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Throughout the week, we have been monitoring the potential for a winter storm this weekend in the Mid-Atlantic. We have finally come close enough to the event for me to issue a preliminary outlook for this system. It is still too early for snowfall maps or exact details to be set in stone. With that said, though, I do think we are close enough for us to begin talking about general expectations for this storm and what we may end up seeing from it. As I have said all week, this is still very much subject to change. I know that people want as much information as possible as early as possible. I get that. However, with the bounds of meteorology today, it is not feasible for me to give you a concrete forecast over three days out. Too much can, and likely will, change. With that said, let’s get into it!
The Setup
As shown in my 10-day forecasts, we will see a shot of bitterly cold air move into the region on Saturday. Current guidance indicates that we may struggle to get out of the 20s on Saturday. On Saturday morning, a northwest wind may make it feel like we’re in the single digits locally. Spots north of DC could potentially see Wind Chill values on either side of 0°. Saturday will undoubtedly give us the Winter feel. This cold air is likely to stick around into Sunday as well, granted it will likely moderate a bit.
Tomorrow, our storm system will track from southwestern Canada through the Plains and arrive at the Gulf Coast on Saturday. At the same time, our area of high pressure will be getting established to the north. How these two systems interact with each other on Sunday will help determine what we see happen in the Mid-Atlantic as this storm turns up the coast.
We have been discussing the different scenarios on the table for this system’s potential track all week. Does it take an inland path thanks to an amped-up Jetstream, does it track along the coastline, or does it take a route just off the coastline thanks to a flatter Jetstream? Today, much of our guidance has come into agreement. The eventual storm will likely be somewhere between an inland and coastal track. That would probably mean a track northward along I-95.
Current Indications
That track near I-95 will lead to several things. It will allow the storm to really tap into the strong moisture fetch off the Atlantic. That fetch will supply ample moisture for this system to work with as it moves northward. The track and the moisture fetch will also allow warmer air to surge northwestward into the coastal plain. Winds around a low-pressure system are counterclockwise. These winds will help bring the warmer ocean water overhead of the coastal plain. While we will have lingering cold air in place from Saturday, the onshore flow of warmer will eventually overcome it. However, areas further northwest of the storm track will be allowed to stay colder as cold air filters in.
How would this play out? This afternoon’s run of Futurecast does an excellent job of depicting a potential solution. You can see the storm lif northward late Saturday before moving into the region on Sunday. We are likely to see precip begin falling after lunchtime on Sunday. With temperatures in the upper 20s/lower 30s, this will likely start as snow for most everyone. However, as warmer surges northwestward, the snow will flip over to a mix and rain. How quickly that happens is dependent on your location relative to the storm track. Locations further inland would see a more extended period of snow before going to rain, while coastal areas could see a quick flip to rain.
This onshore flow could mean that we see moderate to heavy rain at times move into the region. This would also mean gusty onshore winds. Current guidance shows that potential for 30-50mph gusts off the water Sunday evening as the system strengthens. This does raise some red flags for me about the potential for power outages and coastal flooding. It’s a bit early to say with any certainty the extent of either one, but the winds will be something that we have to contend with.
Our region will see a wide variety of precipitation types. Along the Atlantic beaches and lower Eastern Shore will likely see mostly rain. This is because the warmer air will easily flow overhead. A bit further inland, but along/east of I-95, there is likely to be a period of snow. Some light accumulations are possible before a brief transition to sleet and freezing rain and then to rain. The transition from that mix to rain should be quick, preventing significant icing concerns. From I-95 to the Blue Ridge will likely see a more extended period of snow before a transition to sleet and freezing rain and then to rain. Some moderate snow accumulations are possible there before the switch to a mix. The mix could last longer here, leading to some icing issues (but it is too early to say to what extent). West of the Blue Ridge mountains will likely be mostly snow as the warm air will have a hard time getting that far west. This is where more substantial accumulations are likely.
Of course, the details on amounts and impacts are not yet in focus, preventing me from detailing them too much. Those details should begin to come tomorrow.
Summary
The uncertainty with this forecast has begun to decrease, but some does still remain. What has become clear is that we will likely see a moderate to high impact storm move through the region Sunday afternoon through Monday morning. The highest impacts will likely be felt out west, where more snow is expected. A transition from snow to mix to rain is currently forecast for Southern MD as warm air will likely replace the bone-chilling air from Sunday. While we likely will not see a lot of snow southeast of I-95, there are heavy rain and wind concerns as this storm tracks over the region. It is too early to detail the extent of these impacts, but I would not write them off! We will get into more details tomorrow with my First Call forecast. It will be essential to stay away from hype and any snow maps you may see floating around the internet.
Stay with JB Weather for the latest information on impacts here in Southern Maryland. You can always access my forecasts and updates here on the website, on Facebook, on Twitter, and on YouTube. JB Weather is Southern Maryland’s Weather Leader, and I am working around the clock to keep you ahead of any storm!
-JB
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