psuhoffman

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

for those that want to feel better, or worse, for a few hours

Then what are ensembles? What's the NBL? Why do we look at ALL the guidance and not just one model run? If we could create one perfect model that predicts the weather with 100% accuracy down to the second like in BTTF2 then yes, we could just program that one model, sit back, and let it forecast. But we don't have that ability. We know the best models we can currently create are flawed and will not perfectly predict at range. If you are taking them as they are and using them as a forecast that is user error. The skill is seeing all the permutations shown by the various models and interpreting what is most likely to happen within that envelope. The best are better at that...the rest post 300 hour model plots on twitter and facebook.

IMO it probably will be a pretty tight gradient in this type of evolution, which the Euro/RGEM/GFS now all show. The bulk of the precip falls in just a few hours in an incredibly intense bad. Once the thermals go isothermal under that band its unlikely the rain/snow line moves much. The temps surge north as that band arrives then the dynamic cooling stalls it and that is likely where the rain snow line sets up for the duration of that period. So if you end up on the snow side you can quickly pile up 3-6" (I think the higher totals are unlikely) where as just on the other side...womp womp. There isn't that much precip out ahead of it and none behind it where some frontrunning snow or band on the backside could cause some consolation snow for places on the rain side during that main show. It's all or nothing really.

This one is more complicated IMO than some of the clearer examples of storms in the last 5 years or so that I am convinced we lost a 1-3 or 2-4" snow around DC due to warming temps. Plus its not over yet, maybe things trend colder again, I was just pointing out that synoptically I don't see much other to root for than "just be colder". Plus I am not in the mood to argue with the "don't talk about that" crew anymore.

Yea, but isn't that what partially is responsible for the very heavy precip under that trough? The GFS hints at it too but its colder so its ok. But if the Euro is right about the warmer thermals overall, not sure what the win path is there. No trough, no heavier precip, trough, warmer. What are we rooting for there? I guess just the colder GFS thermals to be correct?

Euro and RGEM today kind of made me a little less optimistic. I was thinking that but they both have 6 hour QPF bombs and are still really really warm.

What are you talking about? You use them to make your forecasts. You were asking me what the MSLP and location was just the other night on the euro where it passed our latitude and talking about what we need that to be in order to get snow. You're taking the model output, and adjusting with experience. Using it as a tool. You would have had no idea there was going to be a low anywhere near Ocean City on Saturday evening from that range without the models. We can extrapolate for a day or two using current observations but beyond that we would have no idea what the features important to make a forecast would look like 4, 5 ,6 days from now! You have to look at all the guidance, decide how its likely in error, apply your knowledge of what usually happens to adjust for that error and make your best educated guess. How else do you propose you put out a forecast for something more than a couple days away? If they could make them better they would, its not some kind of conspiracy to hide the real weather from us. It's just the limitations of our current scientific and mathmatecal ability.

@WxUSAF @Terpeast I'm not too worried about the too amped or sheared out options. I think it will end up with the more favorable in between solution. But I am concerned the thermals might bleed the wrong way anyways and even with the more favorable track/intensity it just ends up too warm.