psuhoffman

I AM GOING TO BE POSITIVE HERE So don't miss it, and snow god's don't make me regret it Something to keep an eye on... I wouldn't expect this per say, but if we are trying to be optimistic I see one thing today that leaves the door open somewhat for a better result NW of 95 here. I am using the 3k NAM but I've noticed the same general trend in the euro its just a couple degrees warmer so not quite as close but going the same way There has been a trend on the euro and NAM to weaken that inverted trough or trowal feature and allowing the developing coastal to develop a more closed circulation sooner. This cools the column some compared to earlier runs. If you look close you can see that in the height fields here The result is the column was VERY close to support snow during the most critical 3 hour period from 95 NW. This was the 12z run... That isn't really close in the yellow area. Looking at soundings it was a pretty thick area of close to 2C above freezing in the mid levels. But look at 18z same time It's REALLY close to supporting snow. I looked at soundings, 850 is about the warmest layer and its barely above freezing in this region. One more move the same as this and it would be snow in this area. I didn't cherry pick this hour...it might even be colder the hour before and after if you look. Before After But this is in the middle of a 3 hour period where this area gets .3-.5 qpf. If it were to be 1 degree colder that would mean a 3-4" thump in this area. It's possible, not likely but possible, that if this were to be just 1 degree colder than guidance thinks...suddenly if flips the other way in this area.

Feb 2021

I am NOT saying there is no potential for something good early in that pattern. There is. And maybe that will determine if it ends up an epic run or just a one hit wonder... but perhaps we are rushing the evolution, a common thing. It is possible, the way I play this out in my head, that we get some cutters as the TPV initially is displaced west...then as it slides east it becomes suppressive...then finally it weakens and ends up in the 50/50 space and THAT is when our best chance of a HECS comes, as the flow behind it becomes less noisy and there is room for a juiced up STJ wave to attack the cold left behind. If we want to go for a 2010 style epic season...we get a phased monster as the TPV slides over us...then the STJ HECS a week later!

Getting a TPV stuck under the block comes with risk/reward. If it gets displaced correctly it can be awesome. However, if it gets displaced into Western Canada it creates a SER and cutters despite a block. If it gets displaced too far south it suppresses everything. Personally if I got to choose, which to be clear I do NOT, in a nino and that kind of block I would prefer NOT having the TPV there to complicate things. Just throw a bunch of STJ waves into the east with a block to hold in whatever somewhat cold domestic air we can manage. I like simple. Of course I reserve the right to change my mind in a few weeks as we build a glacier from snow on snow on snow if this goes right. BTW back when seasonal forecasts were coming out I saw some poo pooing 1966 as a "lesser" option because technically there was "less" snow than the more epic seasons. But there was a couple weeks in there where it was truly COLD with snow on snow on snow and one of those storms being a triple phased bomb tucked into the delmarva. Come on, only Ji would come out of that anything but thanking whatever god they believe in.

Agree with your analysis. Having a TPV displaced under the block would make this a much colder look than recent Nino blocking regimes like 2016 and 2010. It would make for a noisier pattern not as good for a long track system. On the good v bad side it would increase the chances of suppression and a 1977 type outcome but it would also open the door to a dynamic phased bomb storm like January 1966. But it would most definitely remove the "it's just not cold enough" part of the equation, assuming we get the TPV displaced far enough SE to promote a favorable storm track.

There is this feature called ignore

IMO the worst Euro run was 0z last night. 6z was notably better IMO, and 12z was SLIGHTLY but probably noise better than 6z. Problem is 0z got so warm that the incremental improvements since don't do much for the immediate DC area, hell they barely improve my chances even, yet. But if we were to see another slight colder adjustment on subsequent Euro runs it could end up improving the NW suburbs chances of some snow.

But it's not really cold enough Below is the mid level thermals heading into the event and I put in purple the bare minimum of where we really want that to be at this point based on case studies of historical similar situations that lead to snow. Now, for your second part...what COULD have changed this part of the equation. Had the NS wave to its NW not been there at all and we had a banana high over the top, or if that was weaker I don't know exactly to what degree changes the equation enough but you get the point. Had the whole thing been faster and the initial NS SW phased partially maybe we get a tighter wound colder system and with that track...that could have worked. There are little things you could adjust to make this snow. I am NOT saying we can't get snow. It's not all or nothing. There are still ways to overcome warming. I think when we get a legit block soon our chances go way up! But 2 things can be true. It's also true that if you cool the entire thermal profile about 3-4 degrees F going into this event then DC is most definitely at the least about to end their 1" less snow streak. And frankly the streak wouldn't even exist within that paradigm because there have been several waves during that time where if it was a few degrees colder (F not C) DC would have likely got at least an inch or two.

I do think perhaps we've reached the end of how bad this can degrade. The track isn't actually trending at all...its just the mid level thermals are trending warmer. There is likely a limit to how far NW of the low the mid level warm layer can get and I think we are close to that now.

maybe someday we can get a perfect track…well ok but it’s a Nina we can’t expect…umm never mind.

Skip to the end if you want the TLDR version We weren't really "in the bullseye". From 8+ days out guidance showed the potential but was all over the place with the track, as it will be from that range. Once it started to lock in on the SW for a few runs around day 8 it was south of us. Then as it caught onto the details it shifted north. There were a couple random runs as that happened that might have jacked DC, but if you pulled back and looked at the average across all guidance over a whole day's of runs...NEVER was DC the bullseye for snow. It shifted within one day from being south to north. Then it settled down for a couple days where it showed DC dangerously on the south edge of snowfall with a WInchester to central PA jack. That is NOT where we want to be 5-6 days out. These things tend to trend north the last 100 hours 80% of the time. Several red taggers said that the last few days. The warning sings were there. These are just basic model trend things. Additionally there is the synoptic setup here. There was no true block. There is a 50/50 but everything is shifted east of ideal because the -NAO is very very east based. We want that ridge centered closer to Greenland to Baffin not where it is. The confluence is pretty far north here. This isn't the right setup to stop the typical trends. There are things that could prevent a storm from trending north the final 100 hours. A crazy block like 2010. Those storms didnt' budge the final 100 hours because they couldnt move north at all there was a wall of confluence over PA. Another option would be a NS feature coming across the top suppressing the wave. Not sure that's even what we wanted here, but the NS is pretty far north and there is no TPV in quebec for a lobe to rotate around like happened in 2014 and 2015 a few times to help suppress a wave without blocking. Not every snow event here follows the standard. Flukes happen. There is always a chance. Even now maybe it trends a few degrees colder and places closer to the city get a thump snow Saturday. Weirder things have happened. But thinking this was a lock day 6 was crazy. I was LOL at some of the posts making declarative statements from places well southeast of me when I was not even comfortable expecting snow up here frankly, knowing the setup and the typical correction in guidance from that range. TLDR version below If you want to feel good about snow in the DC area from 5 days out you need a few things. 1) Truly cold and deep antecedent airmass where the thermal boundary is well south of us as the wave gets its act together in the TN valley 2)A well placed 1030 or greater high 3) A STJ wave tracking at us from the SW, not the NW or not needing some crazy negative tilt system to bomb straight up the coast. Something into the TN valley then transferring to the NC coast is the highest probability snow event here 4) Strong confluence where the flow turns somewhere just to our north, like in central or northern PA, not up in northern New England or Canada 5) a true blocking situation with a 50/50 locked in by a ridge to its north. If you have all 5 of those features then I think its safe to feel optimistic about snow chances in DC from longer leads. Absent those...I would NEVER feel good about snow until it was within like 48 hours because the more of those factors we lack the more we need lots and lots of other variables to go perfectly to compensate. It won't be simple or easy. We really only had 1 of those this time...we had an ideal STJ wave and track. And that does put is at least in the game for a fluke to work out absent other things. But we didn't have all the other things needed to make this an "easy" win for DC.

This feels related to what I was getting at yesterday, if you just look at the features we usually rely on to get a feel for the event, SLP, sfc high, confluence, heights, and ignore the specific thermals, everything has actually been trending BETTER over the last 72 hours. You have to pull back to see it, ignore individual run random bounces, but if you look over the last 3 days and just look at the average of all those features its better now than it was. Yet our snowfall has been slowly slipping away across all guidance over that same period. Because regardless of all those features its been trending warmer. A run would trend southeast with the track and better with the high...and the rain snow line still moved 10 miles NW, and this was happening across guidance, worse on the euro which is another bad sign since it's the best with thermals among the globals. So seeing the GFS trend warmer, even if just 1-2 degrees, I think everyone got that feeling like...here we go. The only thing making the GFS better than the Euro was it was simply slightly colder, but everyone knows which one is more likely correct on that one thing. The annoying thing is there is no trend we need with the amplitude or the high, or the confluence, or the upper low, that stuff is all fine, we just need it to be colder than it is. On the positive side things might stabilize now and salvage some frozen for the NW parts of this forum. I could see a path to a quick thump snow still NW of 95 on Saturday. Also, maybe this is like the storm in early 1987 that gave my area like 6" of slop and was a big interior snowstorm for central PA up into interior New England. Then there were a few more interior storms before the snow hit the coast. Maybe we are on a similar progression here. If there was a true block there might be a pathway for something like this to have worked for DC. The path would have been a phased system that was blocked from tracking too far NW. That would have provided the colder profile needed without an inside track. But without a block...we were left with a really really narrow path here. No phase (or a late phase with the trailing SW which is what this is trending towards) wont work for us, congrats New England. It's too warm without any NS interaction. But a phase would have likely lead to an inside track anyways. I don't think those runs 3 days ago that had a 988 low tracking half way up the Chesapeake bay would have actually been snow in DC come game time, that track was way inside what we needed. And it was likely to adjust further inside if that early phased idea was correct anyways. Once we have better blocking and a 50/50 locked in that's when I will get really upset if a setup like this fails.

Thought I saw a flake…then I finished shaving, went outside and it was snowing lightly.

NAM moved towards phasing that trailing SW in. If that trend continues it’s not impossible to get a little snow Sunday if there is enough cold. Ya i know lol

Getting there but in a case with divergent camps they can still be useful. It the op will be better at details and thermals.

To each other? If not that’s a story I need to hear!!!

The eps has been a false positive. At longer leads the ensemble will have a more expensive snow shield due to spread. As the lead shortens it will tighten up as variance decreases. You don’t want to be near the southern area of the snow ok an ensemble at 72+ hours. As the gradient tightens you’ll usually end up on the wrong side.

Ya I know but I’m not trying to have that fight again. My point was we don’t need a track adjustment. Case in point 18z euro was a little southeast of its 12z track and it’s slightly warmer.

this is what I mean. And ya of course if we had some arctic banana 1035 high instead of the inverted trough to a NS system ya…but that was never the setup. Within this paradigm we got most everything to go our way, as it often does in a Nino, we just need it to trend a few degrees colder. It’s not impossible! It’s a minor adjustment. The NAM was much cooler leading in but it has the wrong synoptic solution. lol. That said given the recent results I’d rather need warmer v colder as an adjustment

Euro took a better track. It’s colder north of us. It’s just now at cold with the antecedent airmass as the gfs. There isn’t any synoptic correction we need other than for it to be several degrees colder.

On a side note the internet is destroying the world. Ya it’s great that I can look up anything at all in 2 seconds. But back when you had to get information from sources with editorial standards we didn’t have to trust everyone to be responsible gatekeepers on BS. And even if you mean well….what if I read an article about some new Xray machine. I’m not qualified to determine the validity of the information. I don’t know jack about radiology tech. And I don’t want to have to fact check the latest radiology advancements. I got shit to do. OK that’s not true I’m just wasting time here and likely looking at synoptic plots of some 1938 snowstorm but I don’t want to fact check that ish. The example I gave is pretty innocuous but the same concept can cause big problems on less harmless topics!

Next time I’ll throw some down to you.

Snow should be gone by Sunday. They get the roads clear fast. 70 and 99 should be ok. I drove to PSU from DMV in snow several times and had no problems. But I use common sense like slow down when it’s icy.

I need to apologize, yours was NOT EVEN CLOSE to the most ridiculous argument on here