TheClimateChanger

NAM caving? I haven't even looked at the sensible weather yet, but the 2M temperature at 15Z on Thursday (what is that about 1 PM, I think?) in Pittsburgh is now shown on the 12z run as 27F in Pittsburgh versus 31F at the same time on the 6z run.

Well, this particular map does include sleet so it’s inflated somewhat due to that in the south. But I liked it because it looks impressive and really screws over the typical north and west crowd.

I think that's the one missing variable. If we can get that boundary through, then winds shift to the north. With north winds, the typical warm nose is non-existent at least at the surface which would allow any mode of wintry precipitation to occur over plain rain.

That's a depth positive change map, which includes sleet as snowfall... similar to this one from Pivotal:

Why are they so different? I think it was hour 72 or somewhere around there... the NAM had Charleston, WV at 55, and the GFS at 32?

10:1 Ratio:

0z GFS (Kuchera ratio):

The 0z GFS still looks like a decent hit.

Well, alrighty then, better get the generator ready…

Here's the updated map through Friday morning. Looks reasonable, except there's a strange band across the SE portion where snowfall suddenly jumps 2+" across no more than like 5 miles.

Not much snow on the NAM, but it does seem to be trending towards a pretty substantial mixed precipitation event. Shows about 1-2" of sleet or sleet/snow mix in the north, with a band of up to an inch of freezing rain through the metro area.

Here's the official NWS forecast through Thursday at 7 PM:

Well, it's supposed to account for melting and other effects. But it's only showing a couple inches of change between now and Thursday evening. It does seem to keep temperatures mostly below 40.

Uhhh, this doesn't look too good...

I like the Canadian snow depth map. This includes snow on the ground now. I'm not sure how these things are generated, as it certainly doesn't really jive with the snowfall maps. But it's fun to look at!

Today's 12z run of the UKMET continues to look pretty good for our region. It's been pretty adamant about the further south track.

Looks like the NWS isn't expecting much. This is area-wide from the current HWO: .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Widespread and periodic preciptation associated mid to late week frontal encroachment will result in mixed wintry precipitation which could need a Winter Weather Advisory. Looks like they aren't anticipating the need for Winter Storm Watches or Warnings anywhere in the CWA. We get advisories for a trace of freezing drizzle so they aren't going too far out on a limb.

I wouldn't get too hung up on the colors. Those snowfall maps with the razor-thin cutoffs are inflating the snowfall relative to the depth change and (incorrectly) excluding sleet accumulations. I mean have you ever seen a (non-lake effect) storm go from 5" in Akron to two feet in Cleveland? Lol.

Much better look. At hour 84 (Thursday evening), the NAM is now showing freezing rain for many places north of the city. Still think it's way too amped, I can't see this wave of low pressure just bullying that 1050-1055 mb high pressing south from Canada. Normally, the biggest player is the low pressure system. In this case, however, the strongest feature appears to be that high pressure pushing south from Canada. I would think that arctic high would have a huge say-so in the ultimate track of this storm system.

Sleet counts as snowfall in the weather records, so if the snowfall maps are completely excluding sleet they are going to come in too low. Normally, it wouldn't make a big difference as sleet accumulations are typically an inch or less. But the GFS shows several hours of heavy sleet with the snowfall maps (even the 10:1) not detecting any accumulation. If that were to actually occur, then yes, 3, 4, 5 inches of sleet are possible, which are being excluded from the snowfall maps. If you get an inch of QPF to fall as sleet at a 3-5:1 snow to liquid ratio, then that's 3-5 inches of sleet.

Nevermind. A big part of the disconnect is your map cuts out substantial snowfall that occurs after 3z Friday. There's still some weirdness going on, but a lot of those places are projected to receive several inches of snow later Thursday night into Friday.

Seems to be a disconnect between the Pivotal snowfall maps and the Pivotal change in snow depth maps. Some areas on the southern edge are projected to have a positive snow depth change of a foot or more, but depicted to receive little if any snowfall.