From the ABC 7 Weather team

Thanksgiving holiday travel concerns

November 22, 2013 - 01:04 PM
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The potential for a coastal area of low pressure to develop around Thanksgiving is increasing. However, big questions still remain.

Remember a few weeks ago, when winter weather was threatening the region nearly 6 days out from the forecast date?

It appears the same type of scenario is happening again, but this time around there is much better confidence for this system to impact the east coast. Let's take a look at the potential impacts next week.

The D.C. area is already expected to experience its coldest temperatures this early in the season in at least 5 years. Cold air will hang around the region this Sunday and Monday behind tonight's strong cold front. High temperatures should only reach the 30s Sunday and near the 40 degree mark Monday.

(Courtesy: WeatherBell Models)

Above is a look at the 500mb relative vorticity plot valid this morning. I've circled two areas of energy, one off the coast of Southern California and one over portions of western Alaska.

We'll be watching for the southern cut-off low meander across the U.S. over the next few days and the energy in Alaska move through Canada and eventually to the Great Lakes by early next week.

When these two finally reach the East Coast, it will result in a big trough over the eastern part of the U.S. As this trough develops, a surface reflection of low pressure is expected to develop over the Gulf of Mexico and move east, transitioning to the east coast late Tuesday into Wednesday morning.

Wednesday morning 6hr-precip and MSLP ECMWF Model (WeatherBell Models)
Wednesday morning 6hr-precip and MSLP GFS Model (Nexlab Models)

As you can see from the model guidance above (to be taken with a grain of salt; still 5 days out), an area of low pressure moves along the eastern seaboard which will have the potential to help spread precipitation along the Interstate 95 corridor just in time for everyone to travel for the Thanksgiving holiday.

7 Day QPF from the WPC

There have been hints that the precipitation could be heavy, with up to an inch or more possible from late Tuesday through Wednesday. The best timing at the moment looks like it would be from sunset Tuesday to sunset Wednesday, with the system long gone by Thanksgiving Day.

Above is a look at the 7 day quantitative precipitation forecast from the Weather Prediction Center. They are also in agreement that the potential for heavy rain is there, but a sharp gradient exists with the heaviest rainfall possible south and east of town with much less farther north and west of D.C.

Right now, the question remains as to what type of precipitation it would be. There could be some snow, but I think the best chance would be relegated to the higher elevations in the mountains.

This is something we'll need to keep an eye on, but latest forecasts are depicting a sufficient amount of warm air in the lower levels for precipitation to fall as rain. The main problem this system will have is that there won't be a big supply of cold air into it as high pressure will have relocated well off the east coast.

The system is expected to clear out the area on Thursday with partly cloudy skies, cool temperatures in the low 40s and along with breezy winds.

Our team will continue to keep you updated on this situation through the weekend and early next week as new developments arise. Be sure to check watch ABC 7 News into the weekend and check our latest posts here online or on our Stormwatch 7 Facebook page for the latest.

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