Wintery mess may threaten Saturday travel in the DC region

- FOX 5 Quick Points:

1) Temperatures fall on the back of some gusty northerly winds through the second half of Friday, with most below freezing prior to dawn Saturday.

2) A weak wave of low pressure riding a stalled frontal boundary south of our region is expected to bring the threat of snow on Saturday.

3) Latest modeling shows light snow in the D.C. region between 5-8am Saturday, transitioning to sleet and freezing rain by the afternoon.

4) This is not a "snow lovers" snow. After three days in a row of above freezing temperatures warming the ground, snow may take a while to stick. The majority of weather models suggest that peak accumulations of 1-2 inches are possible, but scattered and mostly on grassy surfaces.

5) Biggest concern with this particular event is the threat for accumulating ice as opposed to snowfall totals. Snow is expected to transition to freezing rain from south to north during the late morning-early afternoon hours Saturday. Threat will be biggest on untreated streets and sidewalks.

Winter Weather

Winter weather looks to threaten the D.C. region for the second consecutive weekend as cold air returns to the region on Saturday. On Thursday morning, the National Weather Service in Sterling, Va. placed the entire Washington, D.C. region in an enhanced risk for a winter storm on Saturday (shown above). The words "winter storm" are used loosely in this case however, as we are only in this category because of the high confidence in the forecast, but they note that the winter weather is expected to have a "low impact" on our region.

The setup involves a transient area of high pressure sliding across southeastern Canada and through New England during the day on Friday and through Saturday. This area of high pressure allows winter to make a brief comeback by displacing cold air southward and trapping is up against the eastern edge of the Appalachian Mountains, a process called "cold air damming." At the same time, a weak area of low pressure will ride along a stalled frontal boundary draped south of the region.

Winter Weather

The majority of weather models show the precipitation beginning as a light snow just around the dawn hours of Saturday morning. With ground temperatures coming off of a three day stretch of above normal temperatures, including widespread 60s Thursday afternoon, snow may initially melt on contact before beginning to stick to grassy surfaces first. Temperatures within the metro are expected to be marginally freezing, so treated roadways will probably be fine as most snow melts on contact. Untreated and less frequently traveled side roadways and sidewalks may see a little accumulation, and could become slick, particularly north and west of town where temperatures will be a bit colder. As for snowfall amounts, we are not expecting this to be an impactful snow across the region, unlike last Saturday where Southern Maryland and the Eastern Shore got over a half a foot of snow. This system does not have that same energy associated with it, and does not appear capable of producing the higher snow totals. As things currently stand, we favor a dusting to 1 inch of snow for most of the region with the possibility of a few scattered areas to the northwest of the D.C. metro region picking up 2-3 inches. In terms of the raw weather model data wise, if you enjoy snow, you want to be rooting for the American Model (shown above right) which is the most aggressive, showing some moderate snow mixing in and more widespread 2-4 inch amounts. The European (above left) is perhaps more realistic, showing lighter snows with less accumulation but a stripe of 1-2 inch amounts along the Maryland, Pennsylvania border. So if you do not believe us, go ahead and pick your favorite model.

Winter Weather

Perhaps the bigger concern as far as travel is concerned is the potential for the snow to transition over to a period of freezing during the late morning/early afternoon. Warmer air looks like it will begin to push back into the region just above the surface during the afternoon. Locations that fall into the 20s early Sunday morning will have the best chances of seeing icing become problematic, so the threat is once again greatest north of the region. Similar to the snowfall, major highways that are well traveled will likely be fine. At this time, the National Weather Service favors less than an inch of snow in D.C. but about a tenth an inch of ice (shown above) with a little more to the north where temperatures will be colder. The concern is greatest once again for less traveled and untreated roadways and sidewalks. Just a slight glazing of ice can cause major problems, so be sure to use caution if you are hitting the roadways during the afternoon and evening hours of Saturday.

By Sunday, temperatures should slowly rise about freezing across the majority of the region and any icing and snow should begin to melt away. The possibility remains that there could be some scattered areas of sleet/freezing rain around the Maryland, Pennsylvania border but around the D.C. region scattered rain showers are more favored. The weekend as a whole looks rather chilly and gray, all the more reason to get outside to enjoy the 60s this afternoon, and even the 50s on Friday before winter’s chill sets back in this weekend. The good news? Looks like 60s are back come the middle of next week.

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