From the ABC 7 Weather team

Archive for category The Outside Story August 2014

The Threat of Rain Continues This Week

August 19, 2014 - 02:42 PM
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If you like cloudy, muggy and gloomy weather then this week is your week. Fortunately, temperatures will be held at bay, only reaching into the lower to mid-80s for daytime highs Tuesday, Wednesday and Thursday but the humidity will continue to stream into viewing area as the region is wedged between an area of high pressure to the north and an area of high pressure to the southwest (take a peek at the graphic below).

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Courtesy of The National Weather Service Baltimore-Washington

A frontal boundary will also continue to be draped across our region and will continue to meander in the vicinity of central Virginia and the D.C. metro area at least through Thursday. That frontal boundary will be the main forcing mechanism for any showers or small thunderstorms that pop up around the region Tuesday afternoon. This means that generally any rain that pops up will be around the stationary front getting caught up in our easterly flow and will preside mainly just south of the Washington D.C. metro area on Tuesday afternoon and evening. Unfortunately, since there is so much moisture and the fact that there is no element that is moving these cells along quickly, are few could contain isolated downpours. Good news is that I don’t anticipate any widespread severe weather for Tuesday evening and into Tuesday night.

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The frontal boundary is just to the south of Washington D.C. on Tuesday afternoon, draped across Fredericksburg through Southern Maryland and back to the west around the Eastern West Virginia Panhandle.

If you are headed out to Nats Park tonight, just know it will be a little on the steamy side but I do believe that we will remain dry. Plenty of clouds will stick around through the duration of the game against the Arizona Diamondbacks as temperatures drop through the 70s. There could even be some areas of fog that form while you make your way home from the stadium.

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Overnight temperatures on Tuesday will only fall to right around 70 degrees in most locations and warm back up into the mid-80s once again tomorrow. There could be a few peeks of sunshine once again Wednesday but an upper level low, diving out of the northwest, will be headed this way.

A piece of energy out in front of that low will move into the region Wednesday afternoon through Wednesday evening. This means we have a good chance to see some showers and thunderstorms around the region. Most of the activity will die off in the evening hours as we lose our heating from the day but there is a about a 20% chance that a few showers or storms could linger into the late evening hours leading into Thursday.

By Thursday morning, that upper level low (reference the first graphic from the National Weather Service for more information on the upper level low) will be nearing our area, crossing through during Thursday afternoon and Thursday evening bringing us yet another chance of some showers and thunderstorms. This time, there is about at 50% chance of scattered showers and thunderstorms around the region on Thursday.


The best chance for a good soaking rain comes on Thursday but all in all expect less than a 1.00” in total rain accumulation from Tuesday throughThursday night. This will be good because if you have found yourself sniffling a little through the weekend and into the first part of this week, around the D.C. region mold, grasses and weed pollen is all running a little on the elevated side. So it will be good to get some rain to alleviate some of those allergies.

 

ZZZZZQPF or Quantitative Precipitation Forecast shows 1.00” of less of rain accumulation around the WJLA viewing area from Tuesday through early Friday morning

Due to the rain that we received through the first half of August, we are well over our normal averages for rain during the summer (June – August 19th) at Reagan National Airport as well as Baltimore-Washington Airport (in fact, the rain that fell on Tuesday, August 12th put BWI +4.38” over their normal rainfall amount for the summer). Dulles International Airport could still use some rain however, as they are behind a little over 1.50” for rain accumulation for the summer months.

And while we are at it, to be completely honest, I am still not sold on keeping Friday through the weekend dry. I have continued to have it dry in my forecast for the last two days but I believe it is going to be a wait and see game to if this pattern sticks through Friday and into the weekend or to see if high pressure can edge out bringing some more pleasant conditions. Either way, we will keep an eye on it for you and let you know as the picture becomes clearer.

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Rain to return to the region next week

August 15, 2014 - 09:48 AM
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At this point in time, I think a lot of us Washingtonians are wondering where the summer has gone. With temperatures in the 50s to low 60s this morning, and highs only near 80 this afternoon, we'll be 7-10 degrees below average across the area. Looking ahead to the 7-Day forecast, summer is expected to return by the end of the weekend. But with the increasing levels of heat and humidity will come a higher likelihood for showers and thunderstorms.

Morning lows Friday, August 15

The eastern part of the U.S. has been beautiful this morning due to high pressure filtering in behind yesterday's weak reinforcing cold front. Temperatures were thought to possibly break into the 50s at Reagan National this morning, which would have been the first time in 10 years that has occurred, but low and behold, it only dropped to 62 degrees. I'm guessing chalk that up to the warm water temperature at 77 degrees in the Potomac next to the sensor.

Temperatures will rise slightly into Saturday, back into the mid 80s. By Sunday, a cold front currently situated over Canada will move into the region, bringing a chance for showers and storms by the afternoon and evening. Highs Sunday should reach the upper 80s.

Water Vapor imagery from Friday morning

Beyond Sunday, the forecast can be summed up by the one word many of you don't like hearing...unsettled. Monday and Tuesday will feature a chance for storms from a disturbance currently located over the northern Rockies. By Wednesday and Thursday, we'll be under the influence of a trough which is currently over the Pacific Northwest. This set-up will feature dewpoints in the upper 60s all week, along with showers and the chance for afternoon storms.

Forecast precipitation through Friday morning from the WPC

Taking a look at the precipitation forecast from the Weather Prediction Center above, the D.C. area may see 2 inches of rain or more with locally higher amounts through Friday morning of next week. Not exactly something we really need after the terrible flooding last week. Be sure to dust off the umbrella heading into next week!

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Areas of heavy rain in the D.C. area Tuesday

August 11, 2014 - 02:06 PM
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An area of low pressure continues to move into the Great Lakes region today and an associated frontal boundary will bring the possibility of heavy rain through Tuesday. Showers will begin Monday evening, rather light in nature, and will continue to overspread the D.C. area overnight.

Surface map for Monday Evening

The Tuesday morning commute may be a wet one, but the heaviest rainfall is expected to fall Tuesday afternoon and evening. A few embedded thunderstorms will be possible, and some locations may see the potential of 1 to 2 inches of rain with isolated higher amounts.

RPM Precipitation Forecast

Our in-house RPM model shows the potential for much of the D.C. area to be closer to the 0.5" to 1" range, with isolated spots mainly north and west of D.C. with the higher amounts. This is in line with other modeling as well as the excessive rainfall discussion, which is pegging the state of Pennsylvania with the potential for the heaviest rainfall.

While ponding on the roadways will be possible, flooding doesn't appear to be a big threat at the moment. However, if some of the heavier showers and storms begin training over the same locations, some localized flash flooding may be possible, especially by the afternoon and evening hours on Tuesday.

Rain should wrap up for the most part overnight Tuesday into Wednesday morning. Drier air will filter back into the area Wednesday afternoon and at this point, conditions look about perfect Thursday through Saturday with plenty of sunshine and comfortable temperatures in the lower 80s.

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