psuhoffman

If COVID wasn’t going on I would seriously try to organize a group therapy snow field trip right now.

Careful to differentiate between a temporary cold moment due to dynamics and a truly expensive cold airmass. The Feb 10, 2010 storm was cold under the very intense mid and upper level lows that passed right over us. But that storm mixed with rain/sleet at the start all the way to central MD and it was 34 despite 2 feet is snowcover the day before and 38 despite 3 feet the day after at BWI. The temps did drop into the low to mid 20s with a ferocious wind during the height but that was dynamics driven not indicative of an arctic airmass. You remove the snowcover and storms and that week would have had highs of 40-50 degrees. ETA: 2003 had some true cold air masses but it was a moderate modoki nino with a once every 20 years type stable perfect pacific pattern. Yea that would work but it’s super rare and no chance in a Nina and not even a good bet in a nino.

Last thought on the long term climate/pattern thing. Those cpc analogs kind of support my claims. If you were checking the pattern analogs all cold season at no point have they been spitting out shutout analogs. And in some cases they were spitting out very cold/snowy periods. But even at their worst they were mostly periods with some snow. And those take into account the pacific same as everything else. There is ample evidence patterns that worked in the past are not now. The next 2 weeks is a major test. This coming look a -epo with a retrograding block historically leads to cold/snow almost every time. Not necessarily 20” but we should not get blanked from that.

Btw don’t know if this is a coincidence but 79 has been a pattern analog recently ETA: just checked today’s update and low and behold Jan 28 1979 is the number 1 CPC pattern analog

It was but neither of those storms was ever a legit high probability threat to DC. They weren’t the result of an amplified longwave pattern they were spawned by the temperate contrast off the coast due to the cold over a warm Gulf Stream. They were always destined to be coastal scrapers.

I don’t know that 79 fits this but also some storms that were like 20 degrees it still wasn’t really a true arctic airmass from cross polar flow. It was from a domestic cold source but the airmass was very dry and when it saturated we got a very cold storm. But with the pac jet blasting maritime air in we don’t get those “dry” air-masses domestically anymore. Crows polar flow was always super rare. We have to be able to generate enough cold from air that didn’t have to come from Siberia or were in trouble.

We’re talking about the mid latitude jet not the sub tropical stream. It can still snow here. Don’t take this as a “it will never snow again” post. But we also can’t deny it’s getting harder. The frequency of single digit and <5” DC winters is going up consistently. The length between snowy periods keeps increasing. I can play around with the longwave pattern in my mind to dream to ways to snow despite the pac but when I start to have to get that specific and stack factors it becomes less and less likely. Historically “just get a block and force a SW under us” was the path. Now we need that plus 3 other things. Another issue is ridges have more amplitude now. Warmth gets further north. So an epo ridge western trough that might have has a suppressed eastern ridge in some analog 40 years ago...I don’t know if that would even work anymore. I suppose the perfect pattern would be a ridge a little east of where the epo one is this week and a NAO block. So the trough is over the central US but not far enough west to capture tropical pacific and gulf heat and pump the ridge east of it. The southeast ridge would be suppressed by the NAO and the Atlantic can’t add the same heat because it’s down wind. That would work. But that’s so specific it’s just not going to happen that often.

@WxUSAF @frd @cbmclean That period gets brought up a lot and I get it since it was our last cold outbreak but IMO that was not an example of a pattern progression we want to rely on to get snow. First of all it took a progression of steps that aren’t likely to repeat very often. Second even though it got cold it wasn’t snowy, I know @CAPE disagrees lol, and that wasn’t a fluke. When you get a full latitude ridge like that in the eastern pacific it’s usually with a positive NAO. And the trough you get in the east is likely too progressive to lead to a big snowstorm. I know the coast got those big coastal scrapers both years (2017 had a more brief but similar early Jan pattern) but while they were intense systems both were driven at the surface by the extreme temperate contrast created by that cold air near the warm Gulf Stream. They weren’t a response to an amplified longwave pattern. So imo both those storms were never a threat to the 95 corridor in our area. We are too far west. The result was exactly what I would expect 90% of the time from those patterns. Cold/dry with a better chance for a progressive wave amplifying along the baroclinic zone off the coast clipping to our east. That is not a good snow pattern for most of us in this forum. I would feel different if I lived in Cape May. Here is the double bind we’re in with the warmer pac base state. And this comment is pertaining to our longer term chances of snow not specific to now. My pattern progression thoughts have not changed. Our most reliable snow looks are not really super cold ones. Most of the patterns that create cross polar flow and arctic outbreaks here aren’t really that good for snow. But most of our regular old warning level snows historically came from some form of blocking (NAO/AO/Hudson bay) that forced an amplified SW under us and the temperatures were just barely cold enough. Most of those warning events I studied temps were near 32 during the snow. A 20 degree cold powder snowstorm was never common here. We aren’t in the upper Midwest. Our common path to snow was a storm forming along the coastal baroclinic zone and with evaporation and dynamic cooling it was just cold enough. Once in a blue moon we would get the 20 things necessary to all coincide and get some 18 degree cold smoke snowstorm. There are still some rare perfect patterns that would likely work now. One would be to get a pna ridge -NAO pattern that sets in later in winter after a colder profile established in Canada. A rare epo NAO ridge bridge can also work (and will this week if the euro is right) but would be even better if the block was centered slightly northeast of where it’s projected now to prevent the mid latitude ridge from linking up. But think about how specific we’re getting now. When we start needing 12 things to be exactly this that and the other...well 2 years without any snow is what you get. And if you eliminate all the snow we got historically with marginal air masses snow would be VERY rare here. The pac jet does look to retract some next week. Not to historically good levels but to not the raging firehose of hell it’s been. That combined with blocking in Canada and being the core of winter should give us some legit good looks. But longer term we need to say a prayer to whatever gods you worship that the pac jet and warm pac base state isn’t permanent. Yes I know overall it’s warming and there is no denying that but maybe the current spike is a peak in the longer term ups and downs, because no matter what pattern manipulations we do it’s hard to get snow with a huge furnace of heat upwind of us and a raging jet blasting that air towards us.

If I recall the genesis of that arctic outbreak was mid December when a crazy epo ridge that even pinched off into a block near AK for a time went up. It dumped a ton of cold into Canada. Initially western Canada as would be expected with a epo ridge. Then late December a pna ridge went up temporarily and pressed the cold into the northeast. By January the pattern was a convoluted mess as the pacific shifted but the cold was left to linger over the east another 10 days or so.

No one should be getting too up or down over ops at range. But what I do find troubling is how it pertains to longer scale issues when we see runs that end up too warm despite a pretty darn good pattern. That run might not be correct but the models are based on sound physics. They don’t show “impossible things” like Ji says. It’s not good when we struggle to be cold enough to snow in late January with a -3 Stdv blocking event and a -epo. If that pattern is still a struggle it portends larger scale problems regardless of the meso scale outcome. Whether is snows or not next week that’s not a good sign long term.

Don’t confuse my willingness to acknowledge the very real and concerning longer timescale overall patterns and trends with analysis of a specific threat. I still think, and said so, that it snows in the next 2 weeks. I also think there are signs it’s getting a lot harder to get snow around here. It shouldn’t take this many things lining up. Both those thoughts can be true concurrently.

Better let someone know

That’s the one that has the best chance actually. And yea @stormtracker I know it’s day 11 but it’s about the progression. As everything retrogrades once the western trough backs off there is a window there with the blocking over Canada for something to amplify in the east. After that Feb depends on whether the AO stays negative. If so I’ll take my chances recycling the same general pattern but with a colder base state going in. Maybe that works out. If the AO flips we torch.

I liked where the euro was going wrt the whole pattern day 10. Details at that range don’t matter.

You didn’t order the wet blanket?

Yea when people say “if the euro showed something twice in a row it used to be a lock” I roll my eyes. Yea it used to only run to 7 days and only ran once a day. So if it showed something twice that means it was at most only 5 days away and the euro held the idea over what would today be 4 consecutive runs.

Euro is night and day wrt how the block interacts with the mid latitude ridge.

Agree wrt Nina. The last few years weren’t a Nina. The pacific problem has been the same regardless of enso. And frankly we’ve barely had any Nina mid latitude pattern response this year. @CAPE but what is the right pattern? If we have a PNA western ridge there will be a trough off the west coast directing mid latitude pac puke into North America. Historically that worked so long as it wasn’t a full on vortex over AK because the puke mainly gets directed up and over into Canada and mixes with the cold continental air and the result is it’s not cold but not a furnace and just cold enough to get snow here But the last few times we tried that the pac jet was too strong and it completely obliterated cold to our north. Ok so that don’t work anymore. But what else does? If we put that ridge off the west coast as an epo ridge because that ridge will be elongated SW to NE (again stronger pac jet and central pac ridge base state effect) it will dump a trough into the southwest. That hasn’t worked because it pumps a ridge into the east (and news flash the Caribbean/gulf/Atlantic are on fire also lol) and the heat it picks up there pumps a huge ridge. We thought with a block it would (should) but if, and I do mean if because it’s not close to done yet, that doesn’t work then what? And relying on the incredibly rare epo NAO ridge bridge block combination isn’t going to save us often. That’s a super rare look. So where do we want the ridge/trough alignment out west exactly? If a pna and an epo doesn’t work? Yea if we somehow got the once in a blue moon rare broad epo and pna ridge...but that’s even more rare then a epo NAO ridge bridge. That’s not a typical wavelength. The epo and pna are typically opposite. If you get a ridge in one you likely get a trough in the other. And frankly it’s made even less likely with a faster pac jet, and that combo was super rare to begin with. Our best bet is as everything retrogrades because there was an epo ridge ahead of it and some cold got in, and as the pattern shifts back to a trough in the northeast pac there will be a window before the cold gets blasted out of North America again with a trough in the east. But that’s a temporary window that took weeks if factors going in an intricate progression. I fail to see this golden pac pattern that leads to a permanent snow friendly regime here if a +epo/+pna/-AO/NAO (what we’ve had for 6 weeks!) doesn’t work anymore.

The “something” is warmth. Even when the flow is suppressive it’s not even that cold. The storm that gets suppressed south of us this week is just rain. But when something amplifies were walking a thin line because warmth has no problem blasting north at any excuse.

That’s a pretty low bar. I still think the period holds the most potential we will see. I covered why at the end of my post to Frd. This threat around the 25 isn’t a done deal yet either. It’s far enough out to see things reverse. But the last 24 hours of trends have been discouraging. Everyone wanted that N pac trough to relax. It did. And so instead of getting mid latitude pac puke we get a heat flux from the tropical pac up through the gulf and pumps a ridge in front of the trough out west.

Unfortunately it’s not totally different it’s simply a continuation of the trend at h5 and what the natural effect of that is. This 24 hours ago was a block look... This is a full latitude ridge... the high latitude ridge does us no good if it links up with the mid latitude ridge. What makes it a “block” is the westerly flow under the ridge. If it links it just becomes a HUGE ridge.

Read the end of my post to Frd

@frd the epo goes negative from day 4-10. That should be sufficient to get cold into the pattern but it gets muted by mid latitude warmth. But what’s the real issue here? Let’s go through the variants. We’ve had an excellent high latitude pattern all winter. We had a pna ridge with eastern trough for most of the last 6 weeks but it didn’t matter because there wasn’t enough COLD in the trough. The trough west of the pna was blasting WARMTH over the top and the trough under it couldn’t create enough mid latitude cold domestically. Now the pna is retrograding into an epo ridge. But that dumps a huge trough into the west (which has been what happens during an epo ridge in the current pacific base state the last several years). Just throwing that out there for everyone crying for epo help! That trough out west pumps a ridge and too much WARMTH gets added by the TNH pattern out of the gulf and we get too much ridge in the central US. After that the ridge retrogrades to a WPO ridge and the trough pulls back into the epo region and we will go back to pac puke WARMTH flooding across eventually. So where do you want the ridge/trough axis in the pacific? There isn’t going to be a ridge across the whole pac with a huge trough across the whole N American continent. But wherever you put the trough in the pacific to the east of it will be a ridge that taps all that WARMTH and blasts it north towards N America. Everyone keeps saying we need the pac to improve but we’ve tried every pac ridge trough axis. So long as the pac is a raging ball of fire with a 200kt screaming jet what configuration do you think works? That all said @stormtracker is going to ban me probably, but I said a few days ago and still think our “best” chance at something is the 3rd wave in the progression (the one around the 30). As everything retrogrades the ridge there has pulled back enough that we could get something to amplify along the east coast. It’s a temporary window before pac puke starts to invade again but there is a really good window of a few days as the pattern retrogrades and essentially reboots back to where we started. That is often how we get a east coast storm. It’s why we usually warm up soon after.

I do think it’s a valid concern though. The blocking is centered a little far SW and has been trending further south recently. That would actually be fine if we didn’t have a deep western trough, but we do and there will be a mid level response to pump a ridge east of it. The trend the last 24 hours across all guidance is for the blocking ridge and the mid latitude ridge to link up and that wrecks the confluence under the block. If they link we essentially end up with a full latitude ridge and the storm will cut. That trend is there across ALL guidance even the EPS. The just has not gone all the way to a full link like the gfs and cmc...yet. But it’s there... On the eps it hasn’t yet become fatal to our chances but it was more pronounced on the op and it’s trending the wrong way. If that trend continues it will be a problem. The good news is we’re still at a range where details will jump around and change. This could reverse today. But the possibility the mid end high latitude ridge links is a serious threat to our snow chances from that wave.