psuhoffman

both Gfs and euro have a very sharp cutoff between significant snow and nada with waves taking very similar tracks along the boundary. Again very 1994 ish just without the crazy ice on the warm side of the boundary because we don’t have an arctic airmass in place.

But he is somewhat right. That is a day 15 mean though...there is a spread and probably some members that aren't bad. But if the H5 anomalies actually end up centered where that mean has them...we are not getting any snow in that pattern. Any wave of any amplitude would track to our NW. The best we could hope for is some ice maybe from trapped low level cold. That is an awful look for a snowstorm.

Yes because if you are only on the edge of the boundary on a mean...anytime a wave comes along the boundary will be north of you. Like I said in my post earlier today...any wave will have a southerly flow ahead of it and try to lift the boundary. Our precipitation events often come at the warmest furthest north point for the boundary in a given pattern. We need the cold anomalies to be well south of us for our area to end up on the cold side during a precipitation event.

A week ago there was a battle between the GEFS and EPS for this week...the EPS had a great look and the GEFS was mediocre...GEFS won! Guess who is more likely to win this time? lol

I obviously don't think it will be nearly that cold but the similarities could mean the boundary between warm/cold could set up in a similar area...just not as cold on the cold side. But if you adjust that pattern from 1994 50 miles one way or the other it can be great or completely awful. Not far south of DC had nothing but cold rain most of that winter while not far north had one of their snowiest winters ever.

I did compare this pattern to late January into early Feb 1994 yesterday. Wasn't there sort of a similar gradient through our area then? I was in western Fairfax County that year just south of Herndon and it was awful. We kept getting pure ice storms while 10 miles NW of us would get a few inches of snow...and another 10 miles NW of there was getting even more. I visited my cousin in WV about an hour NW of me several times that winter and they had like 10" of hard packed snow/ice cover each time while my lawn was bare. It was torture.

Looks like Ralph settled it... snow line sets up northwest of 95 even with that solution LOL And my book gets a little thicker.

are we taking bets on which

The Sunday wave is gonna be difficult to work out...even for the NW crew, because the airmass in front is just so awful. Even with a pretty good track, if the wave has any amplitude to our west the southerly flow will wreck what little cold there is easily. It's not no hope...but we need a lot to go right. The airmass gets progressively a little better after each of these waves so we have a better chance next week imo.

GEFS is a fucking thing of beauty for next week. Best possible signal in every way from an ensemble at that range. It's the GEFS so take it for whatever you think its worth but damn. See I was ninja'd by everyone lol

@Maestrobjwa I can't answer your question. It's hard to say exactly how much the base state has degraded. It's hard to know what a couple degrees would do. It's not as simply as "its 42 and rain so it would be 39 and rain". Changing the equation some could cause the storm to transfer to the coast sooner moving the whole boundary hundreds of miles after. A storm might not develop at all if its a little colder and the boundary doesn't have enough baroclinic instability to initiate the development. This isn't the best example of warming hurting our climo though. We always struggled to get snow from progressive wave patterns. It takes perfect timing for that to work here. The problem I have been alluding to is that recently what used to be a better way for us to get snow in marginal temperature regimes has been failing consistently because marginal temp profiles are now just flat torches. So now we are actually rooting for a pattern that frankly isn't really historically the best way to get a lot of snow here. But it's also a colder pattern and not a total no hope shutout one so people are rooting for this just to have a chance to get some snow. That's my take on all this.

But there is a logical physical reason for that. We've been dealing with total continent wide torches people forget how hard it can be to get a lot of snow even in a cold pattern around here. I am about to generalize so please don't post every exception to the rule...but 90% of winter precipitation (or at least the type that we are tracking) comes from warm air advancing over cold air. Storms ride along the boundary and in front of any wave the southerly flow will try to push the cold boundary north. That is necessary to getting the WAA precip responsible for most of our snow anyways. But...given our location, northeast of the Gulf, along the coast, with very little elevation....if we don't have some mechanism in the northern stream to prevent the boundary from advancing north...we are going to be toast most of the time unless we just get incredibly lucky with timing. Storms are naturally going to want to lift as they get close to the east coast with all the heat gets added from the gulf then atlantic to the southerly flow of any approaching wave. This is why blocking is so important. Our best setups are when something tries real hard to lift north but it cant...its blocked...and the result is all that warm air trying to press into the cold and we get crushed. But what is way more typicaly is there isn't something to prevent the boundary from lifting and so we are cold behind waves...and warm up as the next approaches. Cold dry warm wet. Its basic wave physics.

I thought we weren't having this conversation in here anymore?

Regarding the day 7 storm...at that range the difference between the 6z and 12z is noise. The 12z actually held the general idea of a more coastal system v the true cutter of all the runs prior to 6z. Go back and compare...the runs from yesterday were cutting the system to kingdom come. Fact is even the 6z with an absolutely perfect track was marginal at best for snow here. This is just a reality we seem to be dealing with no matter what. So we have no margin for error...the 12z GFS synoptic evolution is still pretty good and would have been a decent frozen event (probably mixed) if we had an actual cold airmass in place.

We're still in the game. But I still feel like we're playing a man down here. Look at the 6z GFS. Why is the rain/snow line along 95 with that progression. That's really important because that should have been about as perfect an outcome as DC could possibly hope for, and it was still marginal with precip type issues for 95 and the flush hit was NW of the cities. No wiggle room on a run where everything went perfect. Maybe this makes me a deb but while others were celebrating the run I saw that and it left me more depressed because it shows just how stacked against us the deck is

looks worse than 6z but way better than 0z or the runs before. Things will bounce at that range...I won't really worry about the next wave until we get clarity on this first one. Actually second because there is a wave late this week to clear first and the exact final amplitude of that one affects everything behind also.

In a nutshell the only way we have a chance with this is if the NS doesn't phase in at all over the plains and its the STJ wave that keys development later along the east coast. We don't have the necessary cold airmass for a west to east wave of any amplitude to work here.

I mean't "Nope not gonna do it for us" sorry I was agreeing with you.

@stormtracker let me be clear, if we had a cold airmass in place the setup on the GFS would be fine also...problem is without any true cold in front of it we can't afford the wave to amplify really at all before it gets to our longitude.

nope its still phasing with the NS out over OK. That's game over for us. We don't have a cold airmass in place so we can't survive any southerly flow ahead of the wave. We need perfect timing which is what the ICON gave us... initially missing the phase, sliding east, then developing once the low was due south of us. That is pretty much the only way this works out.

The main change on the ICON is around hour 72 as the system is in the formative stages in the plains its a lot weaker and a little faster this run. That tightens the wave spacing some which helps...the NS also doesn't dig as much as so the system is flatter and slides east more and then phases and develops from a further east location. It's a rather significant change for only 72 hours...if its real the other guidance should see it this run I would think.

Wish it was a radar not any model Yea but on the other hand if we're trying to have some hope the ICON still has better scores than anything that existed 10-20 years ago...its just crap compared to the newest upgraded globals (or GFS before it recently went haywire). But this is the first run of the 12z globals and its at a range where its not impossible that if something shifted the ICON could pick up on it. Doubt it but crazier things have happened. Lets see in a few mins if the GFS and CMC are feeling any of the ICON vibes.

I think the GFS was doing the same general evolution but with the next wave middle of next week. But the concept applies to all these waves. Either way this was a HUGE shift for a relatively short lead time so lets see if the other 12z guidance picks up on it or if its just a hiccup run of a JV model.

BAIT

Those probabilities have a major mathematical flaw. They are simply showing what % of the EPS members show X amount of snow. But those permutations are all based on the same physical equation so they all have the same bias and errors to some degree. The model is unable to calculate what the true odds of snow are because it does not know what it does not know, and that is what is the chance the EPS physics is handling something incorrectly and it has nothing to do with the permutations of the initial conditions. A probabilities based on the ensembles of the GEFS/GEPS/EPS might produce a slightly better true probabilities. It would help if those others put more emphasis on their ensembles like the ECMWF does but at least it would calculate some different physics representations into the equation.