Northern Snow, Sketchy Farther South

Got a few minutes, and no major changes. Before I continue, I will try my best to address most — if not all — on this list, but there is going to be a wide variety of snowfall totals from this storm. Looks like “3 zones” of snowfall… heaviest in the north, a transition zone, then a southern area that gets a fair amount of rain.

Super Quick Take:

Northern areas (from Howard County/BWI and points north… generally speaking, the I-70 and 695 corridor north into srn PA): Looks like mostly snow, with accumulations in the 4 to 8″ range. Could be higher totals if the coastal low sets up in the right spot. Pcp starting as rain this eve, changing over to wet snow by midnight. Snow could be heavy Tuesday.

Central areas (east and north of the DC Beltway to I-70): This area will likely see mostly snow as well (also rain at the onset this eve), but the band of heaviest snow is progged by the models to set up a bit farther north. This could change… but for now, I’ll put this area in a 2-5″ forecast, with the higher totals farther north.

Southern areas (DC South): Rain will cut into snowfall totals, likely limiting these locales to an inch or two of slushy wet snow. But I’ll add this “southern area” may get more snow, esp around DC and immediate burbs, if some of the models are correct.

How it’s gonna play out:

Enjoy the bright blue skies, cos today may likely be the last of the sun we’ll see for the rest of the workweek. We’re in between systems, with a coastal low off of New England while a broad “swirl” of unsettled weather dives southeast from the Great Lakes. This swirl is courtesy of a deepening trof (a southward dip in the jet stream), and what makes this forecast even messier is the number of smaller disturbances (look like eddies) embedded within the swirl.

Non-met/non-technical folks, skip this italicized part…
Geeky sidebar: If you want to see what this swirl looks like on the satellite, check out the water vapor loop; this image/loop shows the movement of the air aloft via water vapor (moisture content) ~ 15,000′ up:

If you’re not really into weather and just want a forecast, don’t bother.

Back to the guts.
This eve (Monday eve)… rain changing to wet snow, but not a big deal. First round of pcp will arrive from the west and southwest, starting as rain in most areas before changing to wet snow in northern MD ~ 10 pm, north of DC ~ midnight, and changing to snow in southern areas in the wee hours of the morning. This snow is not the main event, and when we all get up tomorrow morning, it may not be all that bad out. Dare I say, we may very well wake up to very drivable conditions… wet snow, but treated roads will likely be fine.

Tuesday, models agree a new coastal low will spin up, causing snow to intensify from mid-day Tuesday into Tuesday evening. It’s during this time that the conditions could deteriorate rapidly. Models vary on where the rain/snow line sets up Tuesday; the NAM changes snow back to rain during the day in DC and burbs, while the Canadian has moderate to heavy wet snow falling all the way down into DC during the day. Models also show potential for thundersnow… a classic side effect of a rapidly developing coastal low. Again, I suspect the very drivable conditions Tues morning will become a nightmare in the afternoon if the models are correct. Snow, heavy at times, north of DC. If the Canadian is right, this will include all of DC. If the NAM is right, it’ll be north of DC. Both models did well during the blizzard, so not 100% sure.

Tuesday night: Models have the coastal low departing, but there’s enough energy still left over (those embedded spinners within the overall swirl I mentioned) that snow lingers, especially in the north, until Wednesday morning.

I see no point in second guessing the NWS forecast for this storm, as I think they’ve got a very good handle on it… in fact, when I saw their forecast, I was like “That’s exactly what I was thinking!” … 4-8″ in the north, 2-5″ in the central, 1-2″ in the south.
I’ll share the NWS snowfall forecast links here.

Expected snowfall:
Max snowfall (if things break just right):

I’m sure this will change. Always does… but for now, that’ll do it.


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