From the ABC 7 Weather team

Archive for category Forecast Discussion November 2014

UPDATE: Chances of Season's First Snowfall and Forecast Totals

November 25, 2014 - 07:44 AM
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Today will be a fabulous weather day to travel if you have the ability to adjust your plans at all. All signs are leading to a major travel headache for D.C. and throughout the Megalopolis for Wednesday all day long. We are officially on Stormwatch now. Here are the latest warnings and advisories for our area.

Winter Storm Watch
The pink area is under a warning and most likely to have the heaviest snowfall totals that could reach 6" or more. In the advisory snow will only be a few inches. As new information from computer models continue to pour in, we still have some variations on the solution, so it makes for a tricky one. No big surprise, this is D.C.  Let's start with timing. Here is a look at the most recent Futurecast7 model of the start of rain, transition to snow and sharp ending.
ABC7 Futurecast

The models depict a cold rain to start, mix by late morning, with some hovering or the transition line around I-95 and then ending with snow.

Here are the big three things that you need to know:

METRO:

1)  Starts as rain before dawn, changes to rain/snow mid-late morning, finishes as snow before evening commute.

2) Little-to-no accumulation is expected inside beltway, mainly just wet Roads. If snow rate is heavy enough, up to a slushy 1/2" or inch possible. Watch for slick spots after dark temperatures start around 40 and end just above freezing. Fairfax and Montgomery Counties may see 1-2".

3) Heaviest precipitation will be between 10 a.m. and 3 p.m.

Impact for Potomac Highlands and Mountains:

1) May start as wintry mix or snow in the morning.

2) Snow totals are likely 3-6" with isolated spots getting more.

3) Hazardous roads much of the day. Ending mid-afternoon, but slick spots will stay unless roads are treated.

Challenge: Temperatures. Through the duration of the storm, temperatures are currently forecast to be above freezing in the close-in metro. We've been very warm the past few days, so snow will melt on contact for a while.  There is no arctic air in place, but the storm will create it's own cold. How much is still somewhat in question. Bottom line is that confidence is moderate on this storm and these forecast totals could go up or down still.  Here is my latest forecast snow totals map.

ABC7 Snowfall Forecast Wednesday

Make sure you join ABC7's Stormteam of meteorologists today from Noon-6:30 p.m. on Facebook.  We will take your questions in a live Q & A session about the storm and travel across the country.

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Coastal Storm with Big Travel Impact Imminent for D.C. on Wednesday

November 24, 2014 - 08:15 AM
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It seemed unlikely last week, but now it is almost certain that D.C. will see a strong storm on Wednesday that will bring the first snowfall of the season. The timing couldn't be worse for Thanksgiving travelers. There are still many elements that have to come together. Here is what we know right now.

A cold front will pass our region tonight and stall just to our east in the Atlantic Ocean. Low pressure will develop near the Carolinas Tuesday night into Wednesday morning and head up the coast. It will pull in colder air from the northwest and moisture from the Atlantic to make a travel headache for millions of Americans from D.C. to New England. All of the weather computer models have predicted that there will be a strong coastal storm, but they differ on the exact track. This means it is still uncertain where the rain/snow line is and how much snow could accumulate.

Possible Computer Model Storm Tracks

What can we expect in the D.C metro? Right now, I expect temperatures to be in the 40s when we wake up on Wednesday, leading to the onset of precipitation as a cold rain. As temperatures drop, it will transition to snow in the afternoon. Because of the borderline temperatures at the surface and warm ground with today's record heat, it is going to be tough to get snow to accumulate on roads inside the beltway.  Minor accumulations are possible on grassy areas, but the snow rates will have to be very heavy for that to happen.

Potomac Highlands/Blue Ridge/Mountains:  Temperatures are key here too with upper 30s possible to start the day as moisture moves in. A rain/snow mix is possible to start with before transitioning to snow by late morning or early afternoon. With falling temperatures and elevation, snow will likely accumulate here. It's too soon to put numbers on this, but we may need a whole hand to count the number of inches that accumulate. As temperatures drop further after sunset, roads will become icy.

Computer models are showing a very wide range of possible accumulations. We will have a better idea Tuesday morning so stay tuned for snow band maps. Here is a look at a probability graphic of 1" of snow or more accumulating from Wednesday morning through Thursday morning.

Percentage of Probability of 1" of Snow or More- NOAA

The storm will exit late Wednesday or very early Thursday morning with wrap around snow showers in the mountains. The rest of Thursday will be clear and cold with highs in the upper 30s to lower 40s. A good day to turn on the oven and cook a bird and stay indoors.  The rest of the holiday weekend is looking calm and cool.

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Arctic Blast Brings Record Challenging Temperatures Tonight and Wednesday

November 18, 2014 - 08:49 AM
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Today's bitter arctic blast brought us the coldest air of the season so far and beats last week's cold by about ten degrees. D.C. dropped down into the 20s for the first time and wind chill temperatures were down in the the teens and even single digits in a few spots.

Lows this Morning

Believe it or not, our high temperature actually happened at midnight with 42 degrees and then plummeting temperatures through sunrise. This afternoon will recover a bit, but temperatures only warm a few notches in the low to mid 30s. That is more typical of January temperatures! And it isn't just the temperatures making it feel unreasonably cold. Gusty winds will keep our wind chill factor in the 20s all day long. Wind gusts will reach 25 to 30mph at times. Here's a look at ABC7's computer model forecast wind chill temperatures this afternoon.

Forecast Wind Chill this Afternoon

The wind will diminish after sunset, so that will help, but clear skies means a cold night ahead. Record lows are in jeopardy tonight. The record low for Dulles is 20. I'm expecting to meet or just break that record. Reagan National's record low is 18, and I think we'll miss that by just a few.

Lows Wednesday Morning

Additional records may be set Wednesday afternoon. Highs will only reach the low to mid 30s. We could have the coldest high temperature on record for the date. Here at the stats for that.

Record Cold Highs Wednesday?

By Thursday, we start a slow recovery with temperatures back in the 40s. A dry cold front will pass our area, but won't bring the temperatures down too much more on Friday. For those of you hating on the cold, we'll reach near average temps in the mid 50s late this weekend and should easily top 60 on Monday. The warmer temperatures won't stop there.

 

6-10 Day Temperature Probability

The 6-10 day outlook has much above average temperatures for the Mid-Atlantic and that should last into the first part of December. Hang in there!

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