From the ABC 7 Weather team

Archive for January 2013

Blizzard of 1996 anniversary: Crippling D.C. snow

January 7, 2014 - 05:05 PM
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Just as the Washington area is breaking out of a chilly, but dry weather pattern in early January, the weather 18 years ago Tuesday was one many area residents won’t forget.

What started out as a low pressure across the central Gulf Coast on January 6, 1996 intensified as it turned the corner to the Southeast Atlantic Coast. The low pressure then swung north along the coast, tapping into the warmer Gulf Stream water and excellent upper-level support. By January 8, a strong low pressure was just off the Mid-Atlantic Coast.

The end result was a major, historical snow storm that unfolded across the Washington region (and the entire Mid-Atlantic and Northeast).

wxmaps

♦ Reagan National got slammed with 17.3 inches, which was the fifth largest 3-day snowfall ever recorded at the airport.

♦ Dulles International (with weather records only dating back to 1962), got 24.6 inches, making the Blizzard of ’96 the second biggest 3-day snowfall.

♦ Baltimore measured 26.6 inches, making the second place rank for top 3-day snowfalls.

Higher totals were found in the western suburbs. The Shenandoah Valley got clocked with up to 30 inches of snow. Strong winds produced drifts of 5 to 8 feet! Even the beaches got slammed with snow with 10 inches in Ocean City!

snowtotals

The storm had a domino effect not only on travel and transportation but the economy. Washington was shut down for 3 days with only limited transportation of goods for a week. Metro-rail transit was discontinued at all above ground stations for just about the entire week. The Federal and local governments were closed. Unfortunately, retailers already suffering from loss of sales due to government layoffs and budget uncertainty had to close down stores and malls, leading to an even greater economic loss.

In total, there were 31 deaths in Maryland and Virginia. Most fatalities were due to people suffering heart attacks while shoveling snow, four were related to car accidents and three were linked to hypothermia. One resulted from a metro-rail accident in Maryland.

To make matters worse, two additional snow events later that week added to the misery. A storm originating in Alberta, Canada, that skirted across the northern tier into the Mid-Atlantic (known as an “Alberta Clipper”) dropped another 3 to 5 inches of snow on January 9 while a third storm struck Friday, January 12 dumping another 4 to 6 inches in the D.C. area. A grand total of 2 to 3 feet of snow on the ground and on buildings caused 3 roof collapses, including a nursing home in Clinton, Md., a church in Springfield, Va., and a school in the District.

Washington

Photo courtesy of the Washington Post

Here’s how the 1996 Blizzard ranks with respect to other 3-day major winter storms in D.C. history:

1. January 27-29, 1922 (Knickerbocker Storm): 28 inches
2. February 12-14, 1899: (Great Eastern Blizzard of '99) 20 inches
3. January 7-9, 1996 (Blizzard of ’96): 16.3 inches of snow

In more recent memory, the December 2009 blizzard produced the third highest 1-day snowfall record for D.C. with 15.0 inches while the February 5-6, 2010 blizzard produced 17.8 inches in two days; the 4th highest 2-day snowfall total in Washington’s history.

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Storms: Great Timelapse of Wild Storms

January 31, 2013 - 05:30 PM
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Here is a great timelapse Alex Liggitt recorded of the line of wild January heavy rain and wind that swept across the DC area yesterday.  This is about 2 hours in 40 seconds from one of our cameras at St. John Regional Catholic School just west of Frederick, Maryland.  Make sure to wait until 25 seconds in   

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Flurries to a dusting of snow for the Friday morning commute

January 31, 2013 - 12:29 PM
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The cold front has passed through the region and flooding is still an issue, but the winds have diminished through much of the area and temperatures will return to their winter-like state tonight. Low temperatures will fall back into the 20s to lower 30s across the area and clouds will be on the increase after midnight ahead of the next disturbance. Unfortunately, this system may make morning travel a little tricky if a a few moderate snow bands set up.

500mb Vorticity Plot for tomorrow morning

Above is the 500mb vorticity plot for tomorrow morning prior to sunrise. There appears to be some reasonable energy with this system, though it doesn't have much associated moisture. This would lead me to believe there wouldn't be much more than flurries or some moderate snow showers. The problem is the timing.

Timing: The areas of light snow will be possible tomorrow morning after midnight starting just prior to the morning commute. This would be bad with the salt now off the roadways from yesterdays heavy rain. The most likely timeframe would be between 4am and 9am. If a heavier rouge snow band sets up somewhere in the region, there may be a few isolated slick spots, just in time for the morning commute. I figured I would try to place that thought in your head before you drive to work tomorrow morning.

Here is a model forecast for tomorrow morning at 5am from the 12Z 4km NAM model. It does depict a few snow showers within the area tomorrow morning prior to sunrise. Though accumulations should be light, you know it only takes a few slick spots to make for a horrendous morning commute in the D.C. area.

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Records broken in the D.C. area Wednesday

January 31, 2013 - 11:27 AM
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There are still numerous Flood Warnings across the area today and many of them continue through this evening through the weekend. This is after some areas received over 3 to 4 inches of rain from the training of heavy showers yesterday through this morning. Laurel, MD even had to evacuate its historic district today because of the release of the Howard Duckett Dam. Once downstream, that release of water will also affect Crofton, Bowie and Upper Marlboro later today. You may think that all of the local area rainfall records were broken, but that wasn't the case.

Highest 2-day rainfall totals

The only place to break a daily rainfall record was Dulles Airport, which saw 2 inches of rain yesterday and a 2 day total of 2.32". Not only did Dulles Airport see record rainfall, but also record temperatures. The record high was set yesterday at 72 degrees breaking the old record of 70 degrees set back in 2002. Dulles also broke a record high minimum of 56 degrees which breaks the old record of 54 back in 2002. Can you believe the temperature didn't go below 56 degrees all day on January 30th! Wow.

RIVER FLOODING TOOL

As far as Reagan National, the airport tied a record high minimum of 52 degrees. Area rainfall was below the record, though there was still a good 1.14" total for 2 days. BWI Marshall also had some great rainfall, with totals at 1.96" for two days, though they too were below record numbers. 

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January Frigid : No Global Warming

January 31, 2013 - 07:00 AM
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Sure has been a wild end to January and it really wasn't "frigid" here in D.C.  I used that as a tease: >)  for this.  Have you head of the term "Cherry picking"?  Just as we might selectively pick the best, ripest fruit, in the on going "debate" on climate change and global warming, data and scientific measurements are too often "cherry picked" to support a position or an agenda rather than science.  I created the title of this short blog "January Frigid . . ." for fun and to illustrate the point.  Here is the graph of the January high temperature in Washington. 

ZZZZZ

Was January "frigid"?  Yes it was! But I have to "cherry pick" the 6 days January 22-27 to "prove" it was frigid.  

ZZZZZ

Overall the January 2013 temperature will close to 4° above average.  What does this have to do with the climate change/global warming debate?  Here is a good read from Forbes.  Have you heard some say or have you read headlines that shouted "Global warming stopped 15 years ago"?.  Let's go cherry picking.  Here is a graph from skepticalscience.com that "proves" it.  

ZZZZZ

Of course 1998 was one of the hottest years on record and is a good time to begin cherry-picking.  Global warming is happening, it is real.  That does not mean that every year will be warmer than the preceding year as this more realistic long term trend shows. 

ZZZZZ

Indeed go back to our January temperature graph.  Variable day to day but overall a "mild" January even with those cold 5 days.  I have many friends and colleagues (none are climate scientists)  who still don't believe a 40% increase in the CO2 in the atmosphere has anything to do with the long term trends climate scientists are measuring like this.  

ZZZZZ

More and more people living in areas of the world most dramatically affected by climate change are seeing real changes in their climate and weather.  Don't think these things are real?  Let's go pick some cherries this spring. . .but only the best :>).  Different view?  Future blogosphere is wide open.  What is the best course of action?  Try and stay objective and for every "opinion" piece on either side, think, "How many cherries were picked for this view?"

 

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Wild January Storms

January 30, 2013 - 12:05 PM
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LIVE DOPPLER  |  HD WEATHER MAPS  |  ALERTS

Follow our Stormwatch 7 Page and please send us any pictures or videos if you see any flooding or severe weather. First and foremost, be safe! Stay indoors away from windows if severe weather moves into your area.

2:18am:  Live doppler shows the strongest line of gusty storms moving over the Chesapeake Bay and on the Eastern shore.  There is still one more line of moderate showers moving through Prince George's and Charles counties and eventually sliding off to the shore.  Rainfall tapering off behind this.

2:02am:  Can you tell where the front is?  Temperatures remain in the 50s and 60s across much of the region.  Notice the upper 30 to low 40 degree readings in Oakland, MD, Elkins, WV.  That is the "colder" air that will eventually make it to D.C.

1:54am:  Severe thunderstorm warning for St. Mary's and southern Calvert counties until 2:45am.  This line is moving East at 30mph and is capable of producing 60mph or greater.

1:30am:  Here's a wide view of what's still to come.  The back-side of the system is currently moving through SW VA.  The D.C. area likely has another 2 to 3 hours of moderate rain, before the wet weather starts to taper off.

1:24am:  A flash flood warning now in effect through 4:15 am for all of southern Maryland.

1:08am:  If you live in Charles county and were wondering where the rain was, here it is!

12:49am:  Super doppler showing, once again, two distinct lines of heavy rain.  I feel like we've seen this pattern over and over today. The training rain continues and unfortunately brings more flooding concerns. 

12:34am:  Wind Advisory extended for the entire area through 6pm Thursday.  Winds could gust between 40 and 50 mph at times.  The winds are slowly starting to pick up.

12:17am:  Nothing really new here, but the latest statement from the NWS in Sterling states, "THE EVENT IS TRANSFORMING INTO A FLOOD EVENT. HAVE CANCELED TORNADO WATCH FOR MOST OF THE FORECAST AREA...EXCEPT FOR THE FREDERICKSBURG AREA AS WELL AS SOUTHERN MD WHERE THE ATMOSPHERE HASNT BEEN WORKED OVER YET" - Sterling WFO

11:52pm:  Line of very heavy rain through Montgomery county and into eastern Fairfax county. 

11:13pm:  Rainfall totals as of 11pm.  Click here for a detailed list.  

Ijamsville, MD - 3.34"

Mt. Airy, MD - 3.05" 

Clarksbury, MD - 2.88"

Purcellville, VA - 2.84"

10:46pm: Tornado watch canceled for the D.C. metro area, but remains in effect until 2am over southern MD.  The greatest threat across the entire area tonight is flash flooding. 

10:09pm: Be sure to check out our HD Maps page for the latest watches and warnings, location of the rain in our radar pages along with temperatures and winds.

10:04pm: St. Mary's and Calvert Counties in Southern Maryland have avoided the rain so far but very heavy rainfall is on the way by Midnight as a strong line is currently moving into Central Virginia.

9:55pm: Our Stormscan continues to show very heavy rainfall west of D.C. This will continue to fall across the region over the next couple of hours and will worsen the current flooding issues.

9:43pm: Flood Warnings have now been issued for Frederick, Howard, Montgomery, Fauquier and Loudoun Counties until 3:30am as one to two additional inches of rain will be possible through the next couple of hours.

9:32pm: Meteorologist Ryan Miller pointed out a good fact. Reagan National has only record 1.39" of precipitation for the month of January. That total may be doubled by the time this system exits later tonight. So far Reagan National has recorded 0.41" though that is sure to rise considerably over the next few hours.

9:26pm: Check out the river gauges in your area as they may have gone up a couple feet in the past couple of hours. So far the region remains under any flood stages, though Flash Flooding is on going through parts of the area. If you encounter high water, report it and find another way to get around.

9:16pm: A Flash Flood Warning has been issued for Culpeper, Fauquier, Madison, Rappahannock and Orange Counties in our viewing area until 3:15am. Heavy rain will continue to train over these areas through Midnight or early Thursday morning.

9:04pm: Here are some rainfall totals closer to the D.C. Metro. Rain will continue over the next few hours before coming to an end after midnight, leading to more potential flooding problems.

Arlington, VA: 0.43"    Washington, D.C.: 0.36"

Annandale, VA: 0.43"    Beltsville, MD: 0.46"

8:52pm: There is a new Tornado Watch that overspreads southcentral Virginia including Richmond and central North Carolina including Raleigh south to Wilmington.

8:39pm: Here is a statement from NWS Sterling... "Just got off the phone with 911 dispatch in Frederick Co MD. They report mulitple roads closed due to high water...along with several waters rescues underway...one just completed in the Urbana Area on Peters Rd where a woman was rescued from the top of her vehicle in flooded waters. Will issue LSR shortly."

Remember turn around, don't drown. Be safe out there and please report any flooding!

8:34pm: Here is a look at some of the heavier rain headed towards D.C. in the next few hours. It should continue through Midnight and possibly the early morning hours. Areas of flooding will be possible and some reports of high water have already come in across Loudoun County.

8:32pm:  The severe thunderstorm warning for D.C. has been canceled.  Still a line of gusty downpours moving through Prince Georges county.

8:01pm: Severe T-Storms are now moving through the D.C. Metro with high winds possible along with very heavy rain. There have been some reports of trees down in the area, please continue to forward along to us any reports of wind damage or flooding.

7:52pm:  A severe thunderstorm warning is in effect until 8:30pm for the entire D.C. metro area and Baltimore.  The line of storms moving East are producing blinding rain and strong winds.

7:40pm: Leading edge of downpours approaching Bethesda, McLean, & Burke.

7:20pm: Weatherbug rainfall totals highest over Frederick and Loudoun counties where rain has been falling constantly since about 2pm.  A flash flood warning remains in effect for these areas.  Check out the totals, so far.

7:05pm: A Severe T-Storm Warning is in effect until 7:45pm for Prince William, Fairfax, Fauquier, Stafford, Culpeper, Spotsylvania and Orange for winds that may exceed 60mph. Be sure to track it on Live Super Doppler 7 as it approaches the D.C. Metro and I-95 corridor.

6:32pm:  TORNADO WATCH in effect for the entire D.C. metro area through 2am. As the strong front approaches, there is enough energy in the atmosphere for circulation to develop. 

6:24pm:  New severe thunderstorm warning until 7pm for Culpeper, Fauquier, Greene, Madison, Orange, Rappahannock, and Spotsylvania counties. 

6:04pm: Severe Thunderstorm Warnings are in effect until 6:45pm for Orange, Nelson, Greene, Albemarle and the City of Charlottesville. It is capable of producing winds in excess of 60mph.

5:43pm:  Flash flood warnings in effect for parts of Rappahannock, Warren, Clarke, Fauquier, and Loudoun counties through 9:30pm.  Moderate showers continue to fall over the same areas.  Rememeber to never drive through standing water.  Additional rainfall totals of 1-2 inches are possible.

5:35pm: Here are some of the latest heavy rainfall totals.

Hamilton, VA (Loudoun County): 1.48"

Adamstown, MD (Frederick County): 1.33"

Leesburg, VA: 1.33"

Mt. Airy, MD: 0.93"

5:06pm:  Showers mainly north and west of D.C.  Temperatures considerably coolder, in the 50s, where the rain has been falling steadily over the past few hours.  D.C.A. remains at 70 degrees.  Watching strong storms approaching Staunton from the southwest now.

4:55pm Bob Ryan here.  Here's a short discussion and the timeline though noon tomorrow.  Heaviest rain and wind still coming through DC area 10PM-2AM. 

4:12pm: new mesoscale discussion has an 80% chance of a severe t-storm watch being issued soon to cover the D.C. area from the increasing threat from the storms over southwest Virginia. 

4:05pm  Radar loop over last 2 hours some training setting up from Front Royal to Frederick and Montgomery County.  Local heavy rain next few hours local flooding possible.  Flood watch until late tonight

3:59pm: A Severe Thunderstorm Watch has been issued for southwestern Virginia until 10pm in association with a strong line of thunderstorms that you can see using our Interactive Radar. This line has the potential to make it to the D.C. area later tonight so we will be watching it very closely.

Severe T-Storm Watch for southwestern VA until 10pm

3:35pm:  Late hyperlocal Futurecast coming in shows winds about midnight 50+mph in DC.  You may be woken up by the strongest winds 10PM-1AM west to east

3:27pm: A Wind Advisory has been posted for the entire viewing area until 6am tomorrow. Winds will gust up to 50mph at times through the early morning hours.

3:06pm: Some heavy rain is affecting Loudoun, Frederick, Montgomery, Clarke and Warren Counties along the line. A quarter to a half inch of rain has fallen in many of these areas with some higher totals locally. Here are some of the totals so far.

Woodstock, VA:  0.70"   Martinsburg, WV: 0.59"   Adamstown, MD: 0.52"

Leesburg, VA: 0.47"   Clarksburg, MD: 0.43"

3:00pm: Rain is coming down on our HD weather camera now along I-270 in Germantown, MD at the WeatherBug Headquarters building on Father Hurley Blvd.

2:35pm: Storms continue to weaken as they enter Montgomery County and move into Leesburg as well in Loudoun County. There is still some gusty winds and heavy rain associated. I have seen winds in the mid 30s and rainfall totals up to a quarter of an inch with this line. The southern extent of the line has drastically weakened.

2:13pm: This line of heavy rain and gusty winds will move into the City of Frederick in the next 5 minutes as well as Leesburg, VA in the next 15 minutes. This line still doesn't have any severe characteristics.

2:02pm: Thank you everyone for your reports of heavy rain entering the western suburbs with this line. It will move into Frederick and Loudoun Counties now and towards the D.C. Metro closer to 3pm if it holds together. The highest wind gusts were 41mph in Brunswick in Frederick County, MD and 40mph in Woodstock along I-81 in Shenandoah County, VA.

1:56pm: Be sure to check out this HD camera in Frederick, MD of the approaching line of heavy rain. It should enter in the next 15 minutes or so.

1:42pm: Here's a look at Today's Storm Reports from the SPC. This includes a tornado that went through Adairsville, GA causing damage and potential injuries. There will be more information coming out regarding this storm later today I am sure. Added correction, there has now been a confirmed fatality by the National Weather Serivce of someone hit by the tornado when they were in their mobile home.

Today's Storm Reports

1:33pm: A Mesoscale Discussion was put out for the majority of our area around Noon highlighting the fact that the severe threat would decrease through the afternoon hours. With that being said, this lone of storms is continuing to move through the Shenandoah Valley with some of the stronger parts of the line moving through Washington Co., MD and Berkeley County in WV. Shepherdstown and Myersville down the line should prepare to seek shelter indoors as this line moves into those areas in the next 10 (Shepherdstown) to 30 (Myersville) min.

1:25pm: Here is video of the tornado that went through parts of northern Georgia earlier today. Video Here

1:17pm: The current line of storms west of the D.C. area will move into Hagerstown, Martinsburg and Winchester all along the I-81 corridor in the next 10-15 minutes. Wind gusts to 50mph are possible along with very heavy rainfall, though there are no warnings in place at this time.

1:07pm:

TIMING: We think this first line that is currently moving into the Shenandoah Valley will weaken as it crosses the Blue Ridge. The main timing for the stronger, heavier rain and storms will be closer to Midnight, with the timing even sooner, 10-11pm in the western and far western suburbs. Here is a good look at a trustworthy model showing a line of storms pushing through the D.C. area right after Midnight.

12Z 4km NAM Model Run for 1am tonight

12:49pm: Check out our Live Super Doppler Radar. The line of heavy rain that is currently on it is a low-topped line which should move closer to the Blue Ridge Mountains around 2pm. We currently don't think this line will hold together as it moves east of the Blue Ridge into a more stable atmosphere. That line has already showed signs of weakening as it has been exiting West Virginia.

12:39pm: Here is a look at the current outlooks as far as the risk for severe weather from the Storm Predicition Center. Just about the entire east coast has a chance for severe weather, with the primary threat coming in the form of damaging winds.

Current Outlook from the Storm Prediction Center

12:30pm: Winds are already gusting from the 20 to 30 mph range right now out of the south out ahead of the cold front. Even some of the sustained winds are at or just above 30 mph. This gives a good idea of just how strong this front is.

12:14pm: A Flash Flood Watch is in effect for parts of the D.C. area including the D.C. Metro from 3pm through late tonight. It is a Flash Flood Watch and not a Flood Watch in our area as very heavy rainfall may fall in a very short period of time, leading to Flash Flooding.

HPC Forecast Precipitation for Today

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Washington D.C. weather: Severe storms possible for Wednesday night

January 30, 2013 - 09:51 AM
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Photo: ABC7

After temperatures reached 69 degrees Tuesday, many of us are loving this break from winter. However, by Wednesday night, the consequences arrive in the form of thunderstorms that will drop heavy rain and bring the threat of flash flooding.

A few storms may be severe and produce damaging winds. A Flash Flood Watch has been issued for the D.C. area starting at 3 p.m. A strong cold front has been triggering severe storms all morning from the Great Lakes to the Gulf Coast.  Here's a look at the damage reports from this system in the past 24 hours:  



The Storm Prediction Center has put the entire area under a slight risk category for severe weather, primarily damaging winds in excess of 60 mph.
The front will reach western Virginia and northern Maryland by mid-afternoon.  We could see some spotty showers in D.C. at that time, but the main event will be later tonight when the cold front arrives. The most likely time of showers and storms is between 9 p.m. and 2 a.m.
Here is a look at our in-house computer model forecast, showing the heavy rain with thunderstorms at 11 p.m. tonight:  


The morning run of the NAM model is in close sync with this and shows the squall on top of us around 1 a.m.   


While the brunt of the worst weather will be short-lived, the rain will be heavy during the thunderstorms. Around an inch can be expected in a short period of time, causing flash flooding in low lying areas and in urban areas.


Use caution on the roads tonight. The moisture will cut off pretty quickly after the front passes, and it will be windy and colder Thursday. Some sunshine by the afternoon with a high in the mid 40s. Back into the 30s for highs on Friday.

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February Ahead: Any cold or hope for snow lovers?

January 29, 2013 - 02:50 PM
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A near record breaking end to January and after our 1 week of "cold", here we are into the 70s in some spots.  Sorry winter weather lovers, right now there doesn't seem to be any big change that will bring persistent cold or a major snowstorm our way through the next couple of weeks.  Here is the outlook from the NWS climate prediction center for the first 1/2 of February. 

ZZZZZ

One of the items we look at is the "Arctic Oscillation" which was negative for a bit, as Jan 22-28 was cold.  The AO is very hard to predict but no indication it will go strongly negative which would indicate very cold air heading to the east.  

ZZZZZ

 

 

Finally a long look (past 7-9 days little-minimal skill) at the upper level pattern and it sure looks progressive into mid-February.  Still hope snow lovers for a "big" storm?  Sure always hope but as as we head toward March, the probability of any big late season snowstorm decreases rapidly.  Stay tuned and we'll keep you posted.

 

 

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D.C. Wednesday forecast: Severe weather possible in the D.C. area

January 29, 2013 - 01:13 PM
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The first severe weather outbreak of the season is occurring through the mid-section of the United States today. Damaging winds and the threat for tornadoes are possible from eastern Oklahoma through southern Missouri and Arkansas. This region for potential severe weather stretches even farther with slight and moderate risks for severe storms placed by the Storm Prediction center.

Today's Severe Weather Outlook by the SPC

Above is today's severe weather outlook. Numerous tornado watches have been issued as well as a severe thunderstorm watch. So far there have only been reports of hail and damaging winds, but I assume as the day goes on we'll see some tornado reports as well. There is a higher liklihood later today through the moderate risk regions.

SPC's Wednesday Severe Weather Outlook

The risk shifts to the D.C. area tomorrow as shown above. This is a giant slight risk area, but it extends through the entire cold front, which will extend from the Great Lakes to the Gulf of Mexico. The highest probability for severe weather exists to our south over SW Virginia, the Carolinas, Alabama and Georgia as you can see shaded in red. Our region is still under a risk and damaging winds should be the main threat in any storms.

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D.C. forecast: Big swing in temperatures this week; First severe outbreak too

January 28, 2013 - 03:37 PM
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The past 7 days at Reagan National airport have been much colder than average with a high temperature departure of -11 degrees. Average high temperatures were only 33 degrees, when they usually sit at 44 degrees at this point in January. It was capped off with some light icing for parts of the region Monday morning.

Light Icing in Arlington, VA Monday morning

The week ahead will experience spring-like temperatures before a crash back into winter by the end of the week and into the weekend. Usually my friends tell me it's this kind of week that makes them sick! A frontal boundary will hang around the region tonight and tomorrow, with fog a liklihood tonight and through much of the morning Tuesday. As far as guidance is concerned, we're not sure how much we trust it, as temperatures in the models may reach the upper 50s tomorrow, though if the fog and clouds hang around, it may only reach the mid to upper 40s. The joys of forecasting! Our current forecast is conservative hanging with the low 50s.

Moderate Risk for severe storms Tuesday from the SPC

A strong area of low pressure and associated cold front will develop in the Plains and move into the Midwest over the next couple of days. Severe weather looks likely through the Mississippi Valley tomorrow evening and tomorrow night, with a Moderate Risk for severe storms placed over portions of Arkansas, Louisiana, Mississippi and Tennessee. Severe winds and the potential for tornadoes exists in those regions, and this could be the first severe outbreak of the year.

SPC Severe Weather Outlook on Wednesday

This severe threat will shift to the east coast on Wednesday as the cold front moves in from the west. The Storm Prediction Center had the D.C. area in the possible outlook as of Sunday, but has taken our area out of the severe outlook as of Monday, as there will be little instability to deal with. We still think there is potential for damaging winds though as winds a couple thousand feet above the surface will be around 60-70 mph. Regardless, surface winds will be windy on Wednesday, with frequent gusts from 30 to 40 mph.

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Temperature roller coaster for D.C. and a wintry mix?

January 26, 2013 - 05:00 AM
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Photo: James Joslyn)

January has had its ups and downs in the temperature department, but up until this past week the region was relatively snow-less.  In one week, that all changed.  An arctic front brought bitterly cold temperatures to much of the East and two clipper systems that resulted in some light snow accumulations

No snow for the weekend, but it will stay cold!  The jet stream stays well south allowing the cold, arctic air to stay in place. 

By early next week, though, the pattern begins to change.  A few high clouds will build in late Sunday into Monday, as a warm front approaches.  This front will open the door to some much milder air, but with it comes the chance for some wintry precipitation.  As the warm front lifts north of the D.C. area overnight Sunday and early Monday, some precipitation will develop ahead and along the front.  Temperatures at the surface will be in the upper 20s to low 30s during this time frame, but as warmer air aloft overruns the cold air at the surface, it can mean the dreaded "wintry mix" for folks. Here's a snapshot from the 00z NAM (one computer simulation) at 7am Monday.  The pink indicates freezing rain/ice.  The precipitation is west of D.C. at this time, but it gives you a general idea of the precipitation type and location of the wet weather by early Monday.

Precipitation aloft begins as snow, but when overrunning occurs (which is common with a warm front) the temperature profile, in the atmosphere, warms, so the precipitation will either partially melt or completely melt.  Say it completely melts.  If the precipitation melts through the atmosphere, but then reaches a surface that is below freezing, the precipitation freezes on contact.  That, my friends, is freezing rain.  Sleet has a similar set up; however, there is a shallow warm layer where the precipitation partially melts, but then enters enough below freezing air that the precipitation re-freezes and falls as ice pellets, or sleet.  Here are two ways of visualizing this:

NWS - Freezing Rain Explainer
NWS - Sleet Explainer

Freezing rain and or/sleet looks like a possible set up early Monday, as the warm air slowly tries to move in.  So how warm will it get?  Well, it won't be until Tuesday that high temperatures climb into the 50s.  Here's a look at the forecast temperatures on Wednesday afternoon, according to one computer model.

Temperatures over the Mid-Atlantic will climb into the 50s, which is not unlikely, at this time, to hit 60 degrees!  Keep in mind, we're a few days out, but just a trend and change in the overall pattern.  Don't get too excited, though, mild weather fans.  Look back at that image of the temperatures and notice the darker blues and pinks over the Great Lakes and Upper Midwest.  Yes, that air will make a comeback to D.C. by the end of next week.  It won't be as cold as this past week's arctic blast, but high temperatures by next Friday will only be in the 30s. 

A big temperature roller coaster, indeed, over the next 7 days.  Of course, the Stormwatch7 weather team will also carefully monitor the progress of the next weather system, which could potentially deliver the region with some icy weather come Monday morning.  We'll keep you posted!

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D.C. Snow: Likely but light through the PM rush (Live blog)

January 25, 2013 - 10:47 AM
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6:18pm:  Our Friday snow event is now over.  Thanks for following our live blog today!  We'll be back for the next weather event in Washington!

5:12pm: Here are some of the latest snowfall totals across the area from the National Weather Service.

 

4:39pm:  Last band of light to moderate snow moving through the D.C. metro.   The back edge of the storm moving through Fauquier and Prince William counties  All the snow should be East of D.C. by about 6:00pm.  

 

4:16pm: Here is a nice picture taken from Karl Helmold in Frederick, MD. Thanks for the submission.

4:09pm: Moderate snow bands are moving back into the D.C. Metro, just in time for the evening commute home. At this pace, snow will be coming to an end in the city closer to 6 or 6:30pm.

3:43pm: Take a look at our Interactive Radar. This shows where the back edge of the snow is, currently in eastern West Virginia. We'll continue to see light snow through the rest of the evening commute.

3:17pm: I think one of the crazy things about this snow is how cold it is. Many times when it snows in D.C. it is closer to freezing as often there is a transitional zone from rain to snow through our area. This time that zone is in North Carolina! Take a look at the local temperatures, all in the 20s and even teens. The high today at Reagan National so far is 25 degrees.

3:14pm: Chatting with the team in here we are all confident that the majority of the snow will be exiting the D.C. Metro close to 7pm. The last of it currently is over eastern portions of West Virginia.

3:06pm: Here is a quick video by Senior Meteorologist Bob Ryan.

2:53pm: At least D.C. just has to deal with all snow. In North Carolina, a lot of the state is contending with freezing rain, sleet and snow. The dreaded wintry mix. Icing will make for much nastier commutes in those areas. As I went to school at N.C. State in Raleigh, I know how much winter precipitation and shut down that city!

2:50pm: Here's a live webcam at the University of Maryland. Thanks to our friendly twitter user @Terpweather for the find.

2:44pm: HD weather cameras are showing snow through the majority of the D.C. area. It remains dry south of D.C. where a bit of a dry slot has been moving through. It shows up rather nicely on our Doppler.

2:37pm: I wanted to thank you for all of your reports on our facebook page as well as on the comments below, we appreciate the ground truth reports when all we have to go by are what the surface observation stations are telling us.

Visibility will be an issue in some of the heavier snow showers and a few slick spots may develop rather quickly in the heavier bands so be careful when it's time to head home for the day. This is D.C. after all so you know we're all in for afun commute home!

2:10pm: Flurries to light snow is now being reported in many areas across the Metro and points north and west. This band will continue to affect the region with the heaviest snow showers north and west of the city.

1:40pm: Our very own meteorologist Lauryn Ricketts has been getting reports from some of her followers and friends in the Shenandoah Valley area of light snow now falling there. Winchester, Woodstock and Front Royal have all seen a few flakes out there. Keep the reports coming in!

1:03pm: Dewpoint depressions (or the difference of degrees between the temperature and dewpoint) are high right now which will be the big problem as the region still needs a lot of saturation to occur at low levels in order for snow to fall. This also leads us to say that this will be another dry snow event so it appears if it does snow it will at least once again be sweepable.

12:52pm: Checking out our Live Doppler Radar right now, there is a nice "snow hole" as everyone likes to call it, though it's really just the atmosphere waiting to saturate. You have to remember that as the beam gets farther away from the radar, it is hitting objects higher up as the beam has a tilt to it. In this case, it is hitting snow or ice crystals higher in the atmosphere (virga which is evaporating before reaching the ground) but you can tell it isn't seeing anything at lower levels closer in to the city.

12:29pm: Frederick, MD is now reporting snow. There is also snow showing up in our live camera in western Frederick County at St. John Regional Catholic School.

12:15pm: Here's a good find from our friend Dave Johnson of a traffic cam showing I-68 east of Cumberland, MD. Very slick driving conditions there.

12:00pm: Pavement temperatures are just about all below freezing throughout Maryland. Light snow or flurries have also been reported in Martinsburg, WV.

11:43am: Snow is already falling in the higher elevations far west of D.C. in Western Maryland. Be sure to check our HD Weather Cameras above to see if it's snowing closer to your area!

Snow falling at Frostburg State University

11:18am: Snow is trying to make it into our region during these late morning hours but the low-level atmosphere is still very dry with dewpoints mainly in the single digits. This snow is evaporating as it falls and is something we call "virga".

I assume we will begin to have a few reports of light snow developing in the Panhandle of West Virginia and the mountainout areas to the west, but it will take a while for the region to reach saturation so snow won't move into the D.C. area until much later this afternoon. 

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D.C. Winter: Mother Nature on a cycle?

January 24, 2013 - 08:34 PM
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The winter in D.C. can be summed up in one word: cyclical! Why’s that? Well, let’s take a look at when snow has fallen in the nation's capital.

Note the key dates.... 24 is the magic number!

snowdates

 

The first reported snow at Reagan National happened as late in December as today's snowfall and the first measureable snow was just two days later (the day after Christmas).

The trend is almost the same at Dulles. The first and third measureable snows were very similar in amounts and exactly one month apart. The second measureable snow in December was greater than the first.

Now what’s the common trend at both Reagan National and Dulles? The second storm that came within two days following its predecessor and brought more snow!

This looks to be the case with tomorrow’s Alberta Clipper. Both Reagan and Dulles should get slightly more snow with Clipper #2 than Clipper #1 (this morning’s snow). Click here for the forecast snowfall map for Friday's storm. Instead of two days apart though, the storms late this month are just 24 hours and change apart from one another.

Mother Nature is usually more chaotic than this… but patterns sometimes happen. So, let’s see next month if Mother Nature follows suit. Who wants to bet on a snow say…February 24 or 26?

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D.C. Snow: Another chance during Friday's PM commute

January 24, 2013 - 03:29 PM
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With last night's snow now in the rear-view mirror, our team has been looking ahead for one last run-in with some wintry weather. The forecast for Friday has shown the chance for snow throughout the week, but we're finally getting a much better idea of what to expect. Temperatures again will not be a problem with this system, as everything should fall as snow. It's the timing that will have the potential to make travel difficult, as it coincides with the Friday afternoon and evening escape home for the weekend.

Timing the snow on Friday

You should wake up to cloudy skies or mostly cloudy skies on Friday as clouds stream in ahead of this next disturbance. Temperatures will start off quite cold around 20 degrees in the city and widespread teens through the rest of the region. We still think it will be cloudy, cold and dry around lunchtime, but by the early afternoon, snow will begin to fall. The timing should be closer to 3pm or 4pm for the western suburbs and between 4pm and 5pm closer to the city. Precipitation should continue through 9pm or 10pm before coming to an end.

How much snow is expected?

Earlier this week we saw a larger potential for measurable snowfall, but now, we are expecting another run-in with snow totals much like last night. We think totals from tomorrow's system should range from around 0.5" to 2" across the D.C. area. Latest guidance shows the majority of the D.C. area with an inch or less of snow. The potential for higher totals exists through the mountains (4"+ in some locations).

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D.C. Snow totals: How much fell and where

January 24, 2013 - 11:04 AM
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Snowfall totals have been coming in to the National Weather Service office as well as our station and we have begun to compile a couple of lists. Last night our team was thinking about a dusting to an inch of snow in the D.C. Metro to a couple of inches south for Fredericksburg and Southern Maryland. Overall I would say we did a pretty good job with this system, which is great giving our track record from the past few weeks! Here are some of the area totals.

The highest snowfall totals were in St. Mary's County in Southern Maryland where there was an isolated report of 5.5" in Ridge, MD from a trained spotter and another report of 4" in Leonardtown, MD in addition to the totals above. The National Weather Service compiled a nice list as well as a map that goes with it on their homepage.

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Snow A.M Rush: How Much and When

January 23, 2013 - 04:56 PM
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The area is now under a winter weather advisory overnight. Some light snow is likely late tonight. I put together this late time-line and what to expect where and when.

With the very dry air over us and a fast moving weak system coming through, this is a "moderate confidence" forecast.  On a 0-10 scale where "10" is a guarantee, I give this a "6"- moderate confidence of dusting to 1" overnight.  Keep you posted.

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Light snow possible tonight in the D.C. area (Update)

January 23, 2013 - 02:15 PM
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**Update** A Winter Weather Advisory is in effect for much of the D.C. area through tomorrow morning at 9am with up to an inch of snow possible in and around D.C. and 1 to 2 inches possible south and east of the city.

A weak "clipper" type system appears like it will bring the chance for a few flakes to the D.C. area tonight into Thursday morning. Yesterday I reported that there was the chance for up to a half inch of snow in the region. I still think this is fairly on the right track for the majority of the D.C. area, but there actually may be some pockets of heavier snow totaling up to an inch or two.

GFS 500mb Vorticity plot

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D.C. cold snap: how does it measure up?

January 23, 2013 - 02:05 PM
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We all feel the chill in the air, and this is the coldest stretch we've seen in Washington for quite a while.  I took a glance at historical data to see how this cold snap measures up to the past.

First of all, our forecast indicates that the temperature may not climb above freezing until Sunday, so that would make for 5 consecutive days of a high temperature at or below freezing (Tuesday was briefly 32°) at Reagan National Airport (DCA).  For the sake of comparison, I sifted through historical data looking for the longest stretch of days in recent years with highs at or below freezing. There have been several 3 or 4 day stretches in recent history, but you have to go back to January of 2004 to find a cold snap of comparable length when we had 6 days below 32° at DCA (warmest was 31°).

Before then, February of 1996 was similar and got off to a cold start with high temperatures ranging from 17° to 30°, and the warmest temperature during that time was 30°.  Also, February '96 may ring a bell for something other than the cold, and that was the 8.4 inches of snow that fell at DCA.  The snow pack likely helped keep temperatures down along with the cold airmass that was in place, which makes our current stretch of cold look even more impressive. 

All that said, we're not breaking any records, and this is not the coldest we've been since '04.  This could just turn out to be the coldest stretch at or below freezing since then.  Actually, just back in January of 2009 DCA hit a low of 8°, and so far in this cold snap the coldest reading was 15° earlier Wednesday morning.

Thanks to Ian Livingston (@islivingston) and Jacob Hamblin (@HamblinJ) for helping to fact check. Follow them on Twitter for great, local weather information.

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Snow Friday: Possible and how much

January 23, 2013 - 04:26 AM
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Snow is back in the forecast twice this week, which seems like something big, but both systems may only drop flurries to a dusting across the region. Friday's system is looking less and less organized at this point as it heads east into the D.C. area.

So what has changed in the forecast? One of the things we were watching was the forecast track of the system. As of Wednesday morning, the track shifted to the south of D.C. This would allow all precipitation to be in the form of all snow, but would also bring the heaviest areas of precipitation south of D.C.  In Friday's case, the heaviest precipitation appears like it will fall in southern Virginia closer to the North Carolina border. This would leave the D.C. area with little (if any) snow as the system skirts by the southern portions of the region. As you can see in the graphic below, we're still waiting for that first inch of snow! We're a little behind...

Average first snows at Reagan National

How much snow are we expecting for the D.C. area? With the current guidance, we would be hard pressed to say that we would get more than a dusting. The highest chance for light snow will be south of D.C. closer to Fredericksburg and Southern Maryland. Farther south along the I-95 corridor, there may be a few inches of snow by Friday night.

As far as timing the system, any snow should begin in the afternoon hours and continue through the evening commute before coming to an end Friday night. This will be bad timing as it will coincide with the commute home. There may be a few slick spots as temperatures will remain below freezing and anything that does fall may stick.

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Wind Chill: Does it really feel that cold?

January 21, 2013 - 04:42 PM
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Boy, was it great that President Obama's inauguration and the inaugural parade was today and not tomorrow.  The coldest air in several years is coming in this week and after a very mild winter, WIND CHILL is the weather headline. Is this a real effect or something weather geeks have created?  Think about the last time you were in a crowded room.  Within a brief time the room probably got warm and stuffy.  We are alive, our body temperature is 98.6° and if there are 100s of us in a small space we heat things up.  But if someone turns on a fan, the moving air moves some of the heat away from us and our body "feels" cooler.  A diagram from askamathematician.com. 

ZZZZZ

   WARM BODY NO WIND                                 WARM BODY WITH A BREEZE 

 Now if you go ourtside with light clothing, when the temperature is 10°, but no wind,  your warm body radiates heat into the cold air and you feel cold . . .  get inside.  Now if you go outside (again light clothes-not naked, the neighbors would call the police) when the temperature is 25° and the wind is 20 mph, the wind chill is about 10° and heat leaves your body about the same rate as when the actual temperature is 10° with no wind. A bit simplified explanation but that's what wind chill is.  It sure is a real effect and the "wind chill temperature" is a calculation that tries to give you an idea of how cold it will feel (with light clothing) so you can take precautions and dress as though the wind chill was the actual temperature.  here is a chart. 
ZZZZZ

and here is what our wind chills around the area will approximately be Tuesday morning. 

ZZZZZ

Bundle up and make sure the youngsters are dressed safely heading to school tomorrow.  After this winter so far, tomorrow morning may feel like 50° below zero rather than "only 10°-15°.  We'll keep you posted.

 

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