WxUSAF

I mean, yes, verbatim it’s snowing meteors to beat the band right there. But I do think the euro and NAM are going to find some warmer layers in there and it’s going to be pounding sleet.

Yikes

The HoCo jackpot is a plot twist I did not see coming!

Not at all, assuming you have proper expectations. Now if you’re going all in on the 18z 12k NAM, best to look ahead to D7+.

We've talked a lot about 2/14/14 with this storm and there are certainly similarities. Even down to a northern stream s/w over the Northern Plains. But there was more spacing between them and the northern stream s/w didn't dive south and partially phase with the coastal storm, and the coastal storm stayed offshore. It had a decent antecedent airmass, but the high also wasn't locked in and the 850 temps and surface temps warmed quite a bit during the day. http://www.meteo.psu.edu/fxg1/NARR/2014/us0213.php

It is. GFS/Euro blend is a solid front end for the metro corridor with 3-6". Hard to tell how much rain still, but obviously a huge dry slot. Less surface reflection west of the Apps helps concentrate the WAA right into our area, so we get a really solid 6-8 hours of snow. Hard to see that we'll get a GEFS mean like offshore track, but even one that goes Richmond-->lower DE-->ACY could be a big improvement with limited non-frozen precip while also giving us the best WAA snow.

Icon and GGEM both hit us next Friday. GFS is much more suppressed.

This GFS track probably is good enough for you to add 1-2" of snow as it pulls away Monday. Maybe C-1" for me.

We've gotten a small, but noticeable shift east/south, but it's still well short of putting the metro corridor in the CCB/deform band. So the sensible weather outcome is not much different. Probably results actually in slightly less WAA thump, but gives us better odds of limiting rain before the dry slot. Also we are getting pretty close to getting a little coating back on top at the end Monday as it pulls away.

Just a note...that capture/tuck/stall that the Icon does in south-central VA (and all the other guidance does somewhere nearby as well) is what we dream about. When it occurs 50mi east of Norfolk/Ocean City. That's when the deform band just crushes the metro corridor.

My intuition is farther south = less northern stream interaction = slower. The pull from the northern stream shortwave is what speeds it up once it gets captured and starts moving N/NW.

Near surface could stay cold, but it would briefly torch in the 925-850mb range. That could actually limit the surface wind risk.

Matters to me. It's embarrassing to be beaten by DC

DCA measuring issues aside, if we get an inland runner as advertised, this is a situation where DC could quite possibly do better than places to the northeast (me, Baltimore, maybe even @mappy) because they're farther west and also closer to the strongest WWA thump snow.

Sure, all guidance will use it I expect.

Gefs at 96 hours have been fine before. Now they are useless lol? I mean, I hope not because 6z GEFS mean is perfect for us, but it’s pretty clear they’re missing something for this storm relative to all other higher resolution guidance that also has updated physics.

A few things I saw elsewhere that weren’t mentioned in here: 1. There was an aircraft mission with dropesondes off the west coast, so that will help resolve the upper air features. 2. 0z EPS had almost all members take an inland track. Huge difference between the EPS and the 0z and especially 6z GEFS. Given that the GFS is still a western outlier to the GEFS and we know the GEFS uses older/less capable physics, kinda think you have to toss the GEFS. On a more editorial note, it’s been nice to see the SE move from the GFS, but with the differences seen in the GFS/GEFS, I’m somewhat worried that the Euro/EPS is doing something better than the GFS and it’s still inching westward. Would really like to see the euro move SE today (say by tonight’s 0z runs) to validate the GFS trend.

A faster primary shortwave helps us in a couple ways. It also increases the separation between it and the northern stream shortwave that yanks it north. 18z GEFS shows this we’ll around 96-108hrs. We wanted more separation between this and the ocean low at one point. Now we want more between the northern shortwave. Hopefully we can get more.

The ensemble is a certain number, 20-50 depending on the model system, of lower resolution model runs with perturbed initial conditions. A mean of those members is produced at each time step for any particular variable.

Be very very cautious of that. I’d bet good money there would be a 925-850mb warm layer in there with that solution verbatim. Driving pingers.

The apparent “jump” west is somewhat of an artifact of where the graphics routine plots an L. What’s happening physically is the storm is occluding and becoming vertically stacked as it moves through VA.

12z stopped the bleeding, 18z stepped in the right direction. That's all that's worth taking from that.

Couple thoughts/reminders for this type of storm, probably too early: 1. “WAA waits for no one”. Precip usually comes in fast and early from WAA. This is the “thump” we’re talking about. Snow growth usually is meh in this scenario (not fluffy dendrites), so ratios are typically a bit lower than 10:1. 2. The mix line (watch CC radar, hi @mattie g) is going to haul ass northward. Given the likely CAD in place, I’d wag that there will be more sleet than currently shown. That could cut down on the pretty colors on the snow maps. 3. This is a stacked and occluded low, so it will snow much closer to the storm track on the west side than is typical. Hence why even 50-80mi east could make a huge difference to snow totals.

With a stacked, occluded low, you’ll get snow JUST west of the MSLP track. So yeah, wouldn’t take a lot to stay all frozen for the metros. As @psuhoffman said, the phasing of the energy on the back is really the key here. Delay that a little or have less phasing and it slides more NE instead of N. If people are bailing on this storm, they’re crazy. I want all snow, but I’d take a 4-6” thump (Hi RR!) all day and night.

Thump, mix, dry slot. Can’t tell how long it rains with the 6 hour maps, but I’d guess not a ton.