Stormchaserchuck1

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

Need everything to slow down for that to happen, and it's somewhat of a progressive pattern..

CPC apparently changed their reading some time ago.. and it's ... not even really close. There was a time in September I think too where there was N. Pacific High pressure and they said it was like a +2.5 PNA lol. I don't know.. someone said they keep the old calculation on another website, and that one has been -PNA for the last month. You can see the clear Pacific-North-American 3 wave pattern in the map I posted. It does run into the EPO domain a little, but is mostly south of Alaska and over the Ocean.. a clear -PNA. This also isn't going to be close to one of the most +PNA Winter's on record.. the 500mb map isn't like that at all. I just don't know how the CPC has +PNA in that time if there is a string of High pressures from the Gulf of Alaska to NE Asia! I don't know what to say... maybe it's better just to look at 500mb or SLP maps and make your own call. They also had many +NAO's when there was a Greenland block lately too.. maybe they use something that is completely independent from H5? I don't know..

Good research Larry, like always, but this is not +PNA

I stand corrected saying the PNA has been positive all Winter yesterday. There is something wrong with the CPC's methodology of calculating.. this is a 1-month period of -PNA.. I don't care that the CPC says it was +pna. It's not going to actually be one of the most +PNA Winter's on record..

The pattern is ok... you guys aren't hearing me that, that's not a 50/50 low.. it's too far NE and actually a +NAO. Now +NAO has higher precip correlation, so when the Pacific pattern works you can get an overrunning storm.. that's probably what we'll get, but not a Miller A without south-of-Alaska low 500mb and sustained 50/50 low. Beyond there, I got weenied 10 times for saying this last night... but it's not an impressive cold pattern. The EPO looks to go positive for a few days. The next "threat" after the 20-22, probably right now looks like rain. @psuhoffman The AO pattern has its highest snow correlation when it's deeply negative.. not coming back to neutral or positive. The NAO is what you want to see go back to neutral because its negative phase is so dry... but we are missing a -5 AO here with 2 rainstorms. After that, when the AO goes back to neutral/positive, it's not a favorable pattern for MECS anymore! I know your research says lag, but besides the 20-22 storm, it's not looking like a favorable period, mostly because of lack of deep cold (because by that time it's not -AO)! The index regions do correlate the highest with US temps at Days 0 to +1.

My Christmas tree is still up! One year I left it up until July. Actually 2 years. but July is the record.