psuhoffman

Interesting but the US high res models aren't showing colder/snowier solutions than the GGEM/UK/Euro so...not sure what the point is from a functional POV

After seeing the entire 12z suite I think the issue with the NAM is simply it's weak sauce south of the PA line with the WAA precip. Had the nam looked like EVERYTHING ELSE wrt that it would have been colder.

I don't have access to the Kuchera maps...the UK 10-1 maps are always inflated because they include ice as snow, which in setups like this...makes them look better than they are.

There isn't really a defined, closed circulation low there, it's a trough axis with elongated low pressure along it...slight changes of where exactly the "lowest" pressure point is along the trough axis at any given moment can change where that map decides to place the "L" which makes the change look more significant that it was.

The UK ptype maps had a glitch...shows snow in places that are clearly above freezing at 850 at 15z Sunday. It still has a good thump legit for the area, 6-8" from what I can tell DC north to PA line... but the maps have to be thrown out because its not calculating precip type correctly

I think what it will come down to is the intensity of the WAA precip Sunday morning to midday. The NAM issue IMO is it's a bit lackluster in that regard over VA and MD south of 70. There is a disconnect between the h7 and h85 FGEN and the lift is displaced from the DGZ and the precip just isn't cranking like we need. The mid level temps jump way north during this period where the precip is less than thumpy and it never recovers...you see once the warm layer hits where the heavier precip is ongoing along the PA line it stalls for a while...we need that to happen further south...which it would IMO if there was heavy precip going on to fight the warming. What I would like to see is what the thermals will look like if the NAM comes around to look like what all other guidance does in terms of the precip profile during the 9z-15z time period.

It's the sleet, if you add up the just snow and the just sleet panels...it looks close to that depth map

Yea as I said to DD, the good news from this run was while it didn't actually help us as is...the trends took it close to being a big deal...it's one of those things where it needs to reach a critical tipping point and this got most of the way there...but not enough to significantly change the results...one more shift exactly like this and it would! We were much much closer to a significant snow event here than on the previous run, it just didn't quite get there. SO we still end up sleeting for the same amount of time...but if you look at the thermal profile...its way closer to snow during the day SUnday than it was on the last run

If I am putting my glass half full glasses on, both the 12k and 3k NAM are now very close to a HUGE event for our area...it would only take like a 30 mile adjustment southeast of the snow/sleet line during the 6 hour critical period Sunday midday for our area to go from 6-7" to 15" of snow! It's really close...the warm layer is not very big in our area...so as is it's not a great run, it's within a reasonable adjustment from being much much better.

FV3 was based on the GFS physics I think, and often is pretty close to the GFS so there is that.

I really thought we had a cushion (the thermal boundary is starting out so far south this time compared to those two events you just cited) that DC had at the minimum like 6" of snow before a flip. But the NAM is bothering me...it just blasts the h75 warm later up faster than the precip is advancing once the trough starts to approach and the SW flow hits us...such that it's implying despite how far south the boundary is ahead of this...DC might barely have any snow before the sleet...the "thump" might just be mostly sleet. You buy that?

It's worse for VA up to about DC...it's better for us...but what's frustrating is despite some pretty decent synoptic improvements...I liked the track of the low and orientation of the thermal boundary better...the coastal development...there was a lot I liked about the run...it got significantly worse in the one freaking thing that actually matters the most...it simply warmed the mid layers a little which blasted the changeover to sleet up a few hours faster during the most critical time period. If the thermals from the 6z had held with the other improvements from 12z it would have been a significantly better run.

12k is weird and annoying, in that it trended better in almost every way I wanted...better trough amplification/orientation, better coastal, colder initially...but it trended worse in the one way that matters most, it blasted the mid level warm later up about 3 hours faster...depsite all the other improvements...it basically just said...yes its better synpptically in every way...but lets just make it warmer to F with you.

9z to 15z is really it. DC has to max qpf in that window. NAM last 2 runs had a dryslot limiting qpf during that critical period.

It is but the bigger issue last couple runs was it had a funky dryslot at the most critical time periods when we needed the thump

I’ve decided to just pretend the GEFS knows WTF it’s doing

Rgem was a little of both. It did trend a little SE with the whole thermal boundary but then it also death banded us.

Guidance is trending towards a colder start and a better band out ahead early Sunday. That’s limits the “bust” potential. But we’re also losing the big upside as pretty much everything except the gfs (and we know it can’t see mid level warmth) changes us over now so the 15”+ type solutions are totally gone now. Things have narrowed in on a 6-12” snow to sleet event for most of the area.

Considering NWS has me in 18-24” “could get a foot” seems reasonable. I’d go 8-12 for my area no idea what NWS is smoking.

0z eps and 6zgefs both increased the 10% snowfall quite a bit across the area indicating the chances for a low end bust went down. The 10% snowfall on the EPS is still around 6” in DC and 9” up here. That’s a pretty decent “floor”. GEFS is significantly better of course but it also increases the floor.

@TSSN+ All I’m saying is if you shave 2-3” off the GFS to account for it’s known issue not seeing mid level warmth these are all getting pretty close now. gfs rgem 0z euro

That seems lazy if true, not saying it is. If you look at the skew on the euro it’s clear their algorithm is just wrong and misidentifying p type. It does have some legit freezing rain for you but it also is showing freezing rain for hours where there is a warm layer above 800mb and it’s like 22 at the surface. Thats sleet.

If you look at the euro or 3k skew for the same time its surface temp is within 1 degree. The problem is the gfs cannot see the warm layer at 750mb. It’s not capable of it. This is a known problem. In cases where there is WAA and a mid level warm layer you have to adjust the snow/sleet line NW on the gfs. You can figure out where it should be a number of ways. Least technical is to look at the 3k or euro and say ok now if their Synoptics were identical to the gfs where would they have the snow/sleet line? Then make the adjustment. If you use the GFS snow line in wAA situations you’ll be wrong EVERY SINGLE TIME. It won’t ever see the mid level warming. Caveat…the only way we overcome the mid levels is if the precip is so heavy (death banded) that dynamic cooling can overcome a bit and the heavy precip can mix out the admittedly small warm layer all the better guidance has for our area. That’s not impossible but it wouldn’t be the gfs being correct it would a similar result for different reasons. like if you call a crossing route on 4th and goal from the 5 and the receiver falls down and the QB scrambles and breaks 2 tackles and dives into the end zone. Sure it ended up with a TD, same results, but when breaking it down in film study you wouldn’t say the play worked.

A shit ton of that accumulation along 95 is sleet. Like 3” of sleet! 6z brings in this ridiculous band and dumps close to an inch of qpf midday Sunday most of which is sleet but hey that counts! It also did beef up the snow before the flip by 1-3”.

Gfs has slowly shifted some towards other guidance if you account for the fact it can’t see mid level warm layers and adjust the snow/ice line 20-30 miles NW like you have to. Then it looks identical to the euro and rgem. The warmest guidance shifted colder. The coldest shifted warmer and they ended up converging on about what the euro has shown the last 24 hours. Shocking.