April Fools Snow?

Yes, you read the title right, I am tracking a storm that could potentially produce wintry weather in the DMV, and yes it's on April Fools Day. I guess this year Mother Nature is playing pranks of her own.  I didn't make a post about this earlier because it looked like it was going to miss the DC area except for western Maryland. But now, as models have been shifting the system more east and south, the DMV has a chance to see flakes fall, and some accumulation in our more inland, northern areas. Any part of eastern Maryland, even northeast Maryland, don't have much of a chance with this system. This system will enter tomorrow, but the main chance of snow is Thursday morning, as a cold front pushes through. It will be rain throughout Wednesday for everyone. This isn't a weak system too. A lot of models are showing 0.75-1+ inches of all precipitation amounts(total QPF) for a lot of our region. Dynamic cooling will help a lot here.

NAM(12km):

The NAM shows heavy rain transitioning into sleet, then snow as the low starts to move off and up the coast. It still shows temps above freezing, but somewhat heavy precip rates, so if there's any accumulation, it should be solely on the grass. A lot of areas won't even see any accumulation.

The NAM shows all the way from a coating in SE MoCo up to 3 inches in Northern MoCo. It will melt very fast when the snow stops though, and the April sun angle + temps above freezing will cut down on the totals. However, one thing I do want to point out is that the NAM and other models have been showing lingering snow showers even after the main course of the precipitation is done, and that may hit parts of the DMV at times. Shouldn't account to much, if any, as temps will be likely above freezing.

This is a sounding at around 4 AM EDT. The red represents temperature at the surface, and the green represents dew point. The precip here would likely be sleet because of a warm nose from 750 mb(1.25 miles up in the atmosphere) all the way to 500 mb(2.75 miles in the atmosphere). The snowflake would fall and refreeze into a sleet pellet. There are north/northwest facing winds to bring in cold air at the surface all the way up to around 700mb. It could also be rain though, since the sounding doesn't seem to go too past 0 C(freezing line) in the "cold air" area at 800 mb. There is more room for cold air up in the atmosphere, and the warm nose isn't that big to guarantee rain.

European:

The European shows heavy rain possibly turning into wintry precip(mix/snow) as the low moves off and up the coast. This has 6 hour breaks between pictures, so there would likely be some short of wintry precip in between the time from hour 48 and hour 54. 

Assuming 10:1 ratio(NOT KUCHERA), we don't see any snow ACCUMULATION, but that doesn't mean we will see a snow shower. The snow accumulation is awfully close to us though. It might have shifted a bit southeast, which is good for us.

GFS:

The GFS shows heavy rain turning into heavy snow as the low goes up and off the coast before starting to lighten out as the system moves out of our area. These are heavy precip rates, and would be enough to combat the sun angle + above freezing temps... if they occured.

The GFS shows all the way from a coating to a half inch, with the most snow in NW MoCo. It has trended southeast and stronger for this storm, which is good!

However, there is room for being skeptical when the transition happens. At 4 AM Thursday, the GFS on the precipitation maps shows heavy snow. However, when you look at the sounding, it says the precip type is... rain? The sounding supports it. It shows a warm nose from 875 mb to 625 mb with temps above freezing. Compared to the NAM sounding, the temps are warmer and the warm nose looks strong enough to cause a cold rain instead of snow. There are north/northwest winds up to 750 mb to pull in cold air which is good.

A small change could mean either cold rain or heavy wet snow. Accumulation isn't expected to happen anywhere but grass, and may not occur in the first place too. This will have to be watched, and dynamic cooling will play a big role here. North/northwest winds will start to occur as the low moves off the coast and will bring in a lot of cold air. We want more heavy snow before sunrise to alleviate sun angle concerns, but the transition seems to be happening around 4-8 AM. Even just 1-2 hours earlier would make a big difference in snow accumulation. I will make an update tomorrow with new models plus radar and soundings. Right now, it looks like a coating up to an inch for MoCo, with some localized areas possibly reaching up to 2 inches. No accumulation is pretty possible too. I am confident in flakes falling though.