Stormchaserchuck1

I said it wouldn't be a bomb and would be flatter... reason is there are big differences in the Pacific off the west coast. We have a weak High pressure there, vs east-based-posPNA that a lot of analogs had. That Gulf of Alaska trough digs waves downstream, and you can get a Miller A type system.. that's not the pattern we have for this wave. Little chance it goes back to a bomb/blizzard, unless the Pacific pattern changes.

You're right -- it's 1/4-5, 1980. https://www.glenallenweather.com/upload/richmondclimate/richsnow/GreatestSnows.pdf Here's the fix

Yeah, with the MJO. Scandinavian ridge is building another -NAO bout potentially in the long range, but the +QBO/Weak Nina impact on the Stratosphere has been strong this Winter -- it's been hard to sustain a -AO with such a cold 10mb layer. It's actually been a surprise we've had so many -AO periods, but they generally aren't sustainable with such a fast flow in the upper atmosphere. Fits the seasonal trend of late - we are getting -NAO's, about average to even slightly above average, but they are in continuum less than average.

Warm pattern setting up in the medium-range.. Feb 20 is probably going to be our last wintery threat for a while.

I'll say it again -- I find it interesting that in the Richmond top snowstorm composite, the 500mb trough in the Southeast, US was the 4th strongest 500mb anomaly in the N. Hemisphere. That is so interesting, because it's a 20 day-analog composite of picked-and-choose analogs of Richmond centered snow. So what that tells me is we need those other N. Hemispheric anomalies to really hit. The -NAO extending to the Hudson bay is a big hit -- but the one missing is a <-100dm anomaly off the west coast. At 500mb, there is even a NW, US trough in the Richmond-snowstorm-map! This time we have a slight High pressure off the west coast, meaning that the East Coast trough may not dig as far south, and the wave may be more progressive vs something that really bombs.

After looking at composites of top snowstorms, it's close enough... but you can see that we still don't have a New Foundland Low though.. it's 750 miles away. I just don't think we are going to get a deep/bomb scenario like models are real close to showing. Yeah, the H5 is a little north of Richmond.

I see it as a flatter storm though vs all the deepening that models are showing. It may end up further north, but not as strong riding up the coast. That is because we don't have that deep N. Hemispheric pattern of large waves in the mid latitudes -- extended. It does deepen under the perfectly placed Hudson bay/-NAO ridge though. Historically that +PNA is a big piece to dig th3 southern jet, and phase the northern jet too.. But it's not in a perfect position.

Richmond's 20 greatest snowstorm days since 1948, based on the Feb 20 date. Pretty close to the current projected pattern.. 3 troughs Pacific-US-Atlantic around a -NAO, ridge extending into the Hudson Bay.. That difference off the West coast (ridge vs trough) could be a reason why it will be a flatter storm, vs a more S->N amped one.

Closed 500mb low over Minnesota Low pressure in Gulf of Mexico Crazy potential on the model -- Maybe expect something less extreme in future model runs? N. Hemisphere 500mb pattern is good, but no extreme +PNA or anything like that

15z SREF also looks pretty north

When is the last time we had a >1050mb High in the Midwest for a storm? Seems pretty extreme. The 18z NAM at 84hr has 1054mb. Todays 12z models holding the storm really upped the chances imo. Also, if models weaken that 1050's mb High in future runs, will the storm trend north?

Congrats! It's better to look at 500mb and make your own determination.. a lot of times lately they have called -NAO's, +NAO. There was a 4 year period actually where the H5 over Greenland was +90dm and they had it >+1.00 NAO for the 4 years.. It's ok if SLP disconnected a little, but these are big differences we are talking about! Someone from the NW, US mentioned to me how it was their 4th coldest Jan 15-Feb 15 since 1950.. I was like, in such a +PNA period! Then I looked, and that's not +PNA at all lol.

GFS ensembles make me a little trepidacious.. but they usually mostly follow the OP A few of them show a good hit though.

We get buried on the Euro. I would love this! Another thing too is if we do get a good snowfall, temps should be cool for a while, at least below 40. The upper latitude pattern goes south, but we do hold a trough it looks like for up to 7 days after.

A lot of possibilities on the table. I'd feel better if we had low pressures at the latitude on both sides, closer, a slower mid-latitude flow, but a block over the top can be enough to buckle the flow under it. GEFS did trend stronger with the Canadian block today.. if it times right, we can do a monster. Still a lot of variation though in what could happen imo. You want to see more ensembles showing a hit. Watching closely. It could be a fun storm! Hopefully it holds. I'm not strongly for or against it right now.

We could have a buckled mid latitude jet though.. if that were the case you could say, 1/3 odds, 1/2 odds or whatever.. but it's not an ideal jet stream situation we have as waves west and east of the storm are progressive. Just makes the timing needing to be just right.

0z GFS and 6z NAM completely different from each other at 84hr.. GFS dug part of the Polar Jet a lot further SW.. NAM has less phasing. NAM not the best model though.

It's not about wave spacing, it's about having a nearly perfectly timed wave to get the high outcome. That map shows that there's a lot of moisture though. I just think the high potential is capped, given the larger 500mb pattern.

True, but it is about "threading the needle" a little bit, as we need a perfectly timed wave, which models showed tonight, but I'm just saying there is more potential variance than normal between now and the event.. It's not being held constant by any particular thing in the upper latitudes, except the remains of the -AO block over Canada.

This moisture sure is pretty though

I'm a bit skeptical of a big one riding on the heals of this.. This is at your -5 AO Don't get me wrong the Pacific turns favorable.. -EPO/+PNA is definitely what we want, but I think a 4-10" event is more likely than 12-20". I can see something moving more W->E vs S->N. The pattern is actually pretty progressive, it's just a matter of really good timing, having a trough right under the Canadian block on models tonight. They sharpened the trough, but not necessarily the N. Hemisphere fundamentals. I mean it could happen like that, but there's more margin of error imo, and less high potential too without an east-pos-PNA and further SW 50/50 low. Don't get me wrong, I think there could be a snowstorm. But I'm not buying the MECS just yet.

I understand what you're saying, just know that models have trended toward a warmer high latitude pattern after the 20-22 storm.. They have been bad in the Day 10+ range, but right now I think it's looking like more of a rain threat. Maybe the MJO tendency will overpower.. we'll see.

A trough off the west coast in the NE Pacific would look attractive. Our average temp is in the low to mid 40s.. we need more than flipping the map.

Yeah.. I think its potential is somewhat capped though.. expect more of a progressive wave vs Miller A MECS. But it could trend north..

Block isn't super strong.. +NAO keeps the flow progressive We still can get a snow event out of it though