MAG5035

At some point soon something’s gotta give with this US vs non US guidance in terms of the top end potential. GFS and NAM totals would be an all-time snow event for the Delmarva and at least a top 10 type event for NJ and NYC.

I saw videos earlier today of the ice on the move on the West Branch at Renovo. https://www.facebook.com/nova1962/videos/818644964578280/?idorvanity=105222725398

It looks like they are factoring the NBM in pretty heavily into their forecast, which is probably the best move right now. That’s a comparison of the regular NBM and the v5 NBM which is the parallel one that is eventually going to be the regular operational NBM this spring. The v5 version doesn’t incorporate SREF due to its impending retirement I believe at the end of the year. Actually I’ll just show the relevent slide from NOAA’s presentation on the v5 as to the differences in it and how the blend is made up. https://vlab.noaa.gov/documents/6609493/7858320/NBMv5.0+Overview+for+Evaluation.pdf

It is trying to tuck the low more than 12z and it def made a big step closer to the GFS once it’s further out to sea. GFS still earlier with phasing/storm development that translates to the big amounts it puts out. Main mechanism for us is still the inverted trough, which was more robust with that run. Our “benchmark” for a coastal low is on top the Delmarva or at least right along/near the coast.

It would be an all-time coup for the GFS if its persistent bomb solution came to fruition. But aside from all that.. again there continues to be solid support on most guidance and ensembles for a widespread light to moderate event via the ULL/inverted trough in C-PA even if the coastal ultimately does pop off and track way SE out to sea. I think we’re all in solid shape for a 2-5” type event right now, with the potential for a bit more within eventual placement of mesoscale features associated with the inverted trough setup. What will need to be watched for in the more likely, lighter snow event scenario is timing and rates. This event doesn’t look particularly cold, especially in the earlier stages. Timing seems to be centering on first half of this event possibly occurring during the day Sunday. Later February solar’s getting to a point where a light snowfall rate with temps near freezing won’t accumulate as well. Obviously, more moderate rates will likely be fine, as will whatever snow lingers into a good part of the night Sunday. That could add a bit more range where folks that end up stuck in the light rates see more like an inch vs being in what will likely be a couple of heavier bands that could help deliver a higher end advisory or more. Or the GFS could be right, that would be good too.

It looks like primary wintry threat in the advised area is going to be some elevated freezing rain accrual and perhaps a bit of sleet, as some low level CAD takes a bit of a hold tonight and advects temps near freezing near the surface and 925mb from the NE. Flood watches here tonight, something I haven’t seen in a hot minute. This first batch of rain has already delivered over a half inch here in the last two hours or so. Think the main thing is ice jam potential but looking at the flash flood guidance it is actually quite low. We basically melted out completely here the last couple days, so that top layer of ground is saturated and probably not completely thawed either. Good chance for some sharp rises in the local waterways. Otherwise a much needed rainfall.

This has actually been the most consistent part of forecasting this the last couple days, the inverted trough/NORLUN feature plus the general lighter snows having to do with the upper level feature dropping through. The last couple model runs have been fairly consistent across the board with delivering a light to moderate snowfall. The 0z suite is solid in C-PA, Euro included, with ensemble support for such things. What is still wildly different is the evolution of the coastal itself. 0z GFS threw down like 30” on a big part of the Delmarva, while the 0z Euro has 1-2” at best there and way offshore with the developing coastal.

There’s a lot of energy pieces in the 500mb flow to sort out. It looks like the main piece is phasing in later on guidance now, firing the coastal more offshore. That deep 500mb shortwave still passes over us, so could still have some lighter snow in that scenario. One thing that I saw hints of in various intensity across the overnight op guidance is presence of an NORLUN/inverted trough type feature… something that just occurred in New England a week ago. That’d be a more localized thing, and probably something hard to nail down the exact location of. 6z GFS had the feature a good bit further west vs 0z GFS, for instance. Then there’s the 84 hr 6z NAM with the wave coming through a full 24 hours early, full disclaimer on it being the 84 hr NAM. But I certainly wouldn’t say the models have a handle on this yet.

In what has been a pretty good indicator of warmer times ahead for us the last few winters, Mammoth Mountain point and click has 59-93” in the grids from now through Thursday lol. I do like the weekend timeframe if we can line something up at the proper time. There looks to be 2-3 different waves this week… Wed, Fri, and then the Sunday system that has occasionally shown up as a snowstorm. The first two waves favor rain with some potential for mix NE.

We’re cooked in the low levels up thru 925mb or so, the easterly/northeasterly flow from the low going to the south is drawing sub zero 925mb air thats in place from that direction.. hence the backwards changeover. Actually a pretty decent band of precip running along the I-80 corridor from State College over to pretty much NJ, and there’s accumulating snow on the cams on I-81 and 80 near Hazelton and down I-81 as far as at least the US 209 exit north of Pine Grove.

No worries, I didn’t at all take it as any kind of criticism. I did think it was funny that I pretty much gave this storm 2-3 days up to the 48-60hr range for it to come back north and then of course it does right after I made my “it’s probably not happening” post. So now a period of steadier precip happening with this looks fairly likely, certainly from the turnpike south but perhaps as expansive as from I-80 south. Big issue now that’s happening with guidance overall is suggesting the lower column might not be cold enough. GFS has obviously been the coldest solution in that regard, but high res NAM, HRRR, Euro to a degree present that this might start as rain and possibly remain so for a majority of the event. While surface temps probably won’t be as warm as today (likely more high 30s to low 40s), there’s depth to the low level warmth in the column all the way up to about 850mb. 925mb (3000 ft) temps are progged as much as +5-6ºC prior to precip onset on most guidance. That makes a rain start pretty likely. Colder sub 0ºC air at that level eventually tries to advect in from the NE as the storm deepens as it gets off the coast. GFS does it the fastest, hence its snowier solution. Euro draws it in late, which leads to measurable snows more in eastern PA. High res guidance like the 3k NAM isn’t drawing it down in time.

I mean I’ll gladly be wrong haha, though I didn’t completely shut the door on precip making it into southern PA. The 0z GFS is going harder than the 18z did, with a warning event in the Sus Valley and advisory all the way up through the C-PA I-80 counties. The northern feature is notably sharper and more involved than the 12z and 18z run. 0z vs 12z Models like the NAM and RGEM which hadn’t been anywhere near getting anything into PA now have lighter precip into the southern third of PA on the 0z run, although p-type is mainly rain with those models. 18z Euro, which was one of the few that got precip into PA was the same as well being similar in precip coverage to 12z but more rain. So temps are still a potential issue as they will be fairly mild Sunday. The GFS’s stronger solution would likely take care of that problem as that solution obviously has the heavier rates. You can see how a lighter event might still have issues though with the marginal surface temps. We’ll see what happens the next couple runs.

I’ve given it a couple days but I do believe this Sunday storm possibility is pretty much cooked for us. The streams look to stay separate and this southern stream wave looks to shoot straight out under us. Still a possibility precip gets into the southern tier below the turnpike, as the op Euro and GFS still suggest but other guidance doesn’t get anything into PA. Some EPS support for the Euro op with measureable snow into PA while the NBM has virtually no swath of snow now.. as GEFS, Canadian ensemble and short term guidance like the NAM et al don’t get precip into PA. AI Euro an outlier showing a more substantial snowfall in the Sus Valley and warning amounts in Philly/NJ. Overall, it’s something I’d put at like 20-30% for a chance of a period of lighter snow in places like Gettysburg-York-Lancaster. Other issue in the event we get precip into southern PA could be temps. They look to top out near 40 Sunday and then likely only cool to around freezing during the timeframe of any impacts of the storm. P-type should be snow as I think the column would cool enough but I think surface temps would make any impacts (roads, non snow surfaces) minor.

Nice day with 48ºF here currently. Some melting but dewpoint’s around 30 and it’s not all that windy today. Eastern PA holding onto chillier temps as progged, while temps did overachieve in the central and western parts of the state today. SW PA is way into the 50s. I see a lot of guidance the last couple runs are killing the storm threat for the weekend taking it way south, but I’m gonna remain indifferent to that prospect for now. Sure it could happen, but we’re also currently in that time range where models like to do such things for whatever reason. We went through a good bit of this with the 1/25 storm as well. So I’m not writing anything off yet.

It’ll def be warmer this week overall and much more comfortable compared to what we’ve been dealing with, though the only “warm” day with respect to average looks to come tomorrow. If temps manage into the 40s that’ll make for daytime highs that aren’t much more than a few degrees above average. Western and actual central probably get there but a lot of guidance suggests the Sus Valley doesn’t even get out of the 30s. Tuesday night temps will stay up and probably have more of a + departure but we’re already bleeding cold air back in by that point behind what is now mostly a dry frontal passage. Rest of the week looks like a continuation of below average temps, although much closer to normal. Then we’ll see what this weekend system does. Snow prospects look to hinge on degree of secondary development to the Mid-Atlantic coast as we will likely have a more marginal cold airmass to work with. Overnight Euro was more of a cutter hence the brief mix to rain solution. GFS and Canadian further south with the primary and has the defined secondary low (esp Canadian solution). I’m thinking high probability this isn’t a clean system (strictly snow), but also good possibility of at least front end snows. Immediately beyond that potential system this weekend we look to more significantly moderate temp-wise for a time next week. WPO is forecast to head significantly negative again in the longer term, reloading Canadian cold. Continued +EPO/-PNA in the progs may mean that focuses out west at first, I think we’ll continue to be more vulnerable to cutting systems in that timeframe (next week). We should welcome precip in any form and any kind of a more active storm pattern, because we’ve been building a pretty sizeable negative departure the last 6 months in basically the entire East. If we get this weekends system, that would make 3 full weeks since the last significant precip maker. 90 day precip departures 180 day departures

Geesh, I guess not. I’m probably in the minority here but I’m not really all that impressed with the wind threat if we’re talking strictly from a mph standpoint. Most guidance and that includes the high res stuff like the HRRR that normally ramps up surface winds barely support advisory winds much less anything of the variety that would cause widespread power outages. But I could get on board with a wind advisory for 45-50mph I suppose. Basically a typical wind event in other words, it gusts to 60mph at @canderson’s house in those anyways haha. This event also has a more northerly trajectory to the wind as well being more NW or even NNW.. less of a direct downslope component to enhance wind gusts IMO. What I am impressed with is the COMBO of the winds and cold temperatures. Dynamically this will be the coldest shot of the winter to date. The more northerly component to the wind minimizes modification of the airmass source travelling over the Lakes, which already have a good bit of ice with Erie >95% covered. Non-diurnal “High” temps for Saturday will occur before about 3-4am Sat morning. Sat daytime temps will struggle to get out of the single digits in most of the area. Laurels and some north-central might not crack zero. You can see how there’s an appendage of non-modified Arctic air that reaches PA. I drew the rough surface wind direction. It mostly goes over the frozen portion of Huron and Erie. Saturday morning will probably be the worst for wind chills, though it won’t be good all day. I think most of that extreme cold watch has a good chance of being upgraded to the full blown warning. Here’s the kind of wind chills the 18z HRRR put out after daybreak Saturday morning. I haven’t really seen those kind of wind chills since the Christmas 2022 cold shot.

UNV got to 25ºF today, with similar temps around town up there. So it stayed at 7 days, which is still tied for the 2nd longest streak to that 1893 streak of 10 days. AOO broke their longest yesterday (that station only goes back to 1950) and added another day today only reaching 18ºF. That’s interesting that for the month as a whole, last January was actually colder.

This winter has been tracking similarly to the last real consistently cold winters that we had back in 13/14 and 14/15, especially the latter. Main drivers then were heavily Pac influenced with a strong and persistently negative EPO and WPO much like we’ve had most of this winter so far other than when we warmed up for a couple weeks in early January. That alignment directs a continental source of cold air from Canada with no Pacific modification. The 13-15 winters achieved that without much help from any -NAO/AO, something we actually have had a good bit of this winter, and currently. The result has been a lot of cold in the east, and a historicially bad winter snow-wise in some parts of the west to date. So with that said, I’ll offer at least a little bit of hope. Starting to eye the following week after this week for some kind of period of modification after we probably get whacked with a couple days of arctic air comparable to what we just had next weekend. Looking at teleconnection forecasts right now, there’s a pretty sizeable shift progged to occur in the Pac realm occurring around the timeframe of that clipper and ensuing arctic shot. EPO and WPO both reverse to positive, and the monster +PNA we have reverses to negative. That combo will almost certainly inject Pacific modified air into the CONUS to some degree. How much negative NAO holds will probably have a hand in how that works into our part of the country. Nothing really reverses the -NAO/AO but some ensembles neutralize a bit more than others. So there could be some resistance here, especially with a solid snowpack in the Northeast. Resistance could in fact end up breeding more snow/mix events in our neck of the woods. But I’m currently thinking we’re looking at a milder pattern overall during that timeframe either way. And you can see the op runs of the GFS/Euro in the longer range sort of reflecting that shift. This week prior to the clipper won’t be all that bad temp-wise either, at least during the day. We will continue to have very cold nighttime lows with a deep snowpack and mostly fair weather (other than maybe Wed for some).

System wise this coming week I don’t think we’re dead in the water yet for the Wednesday system, especially in the southern half of PA. NBM guidance has measurable from roughly the turnpike south and GFS generally in that ballpark. This certainly has time to trend back our way, though I think it would just be a lighter snowfall on the table. Solid agreement beyond that for a strong clipper tracking SE thru the lakes around the Fri-Sat timeframe. While staying plenty cold, low track north of PA might have the typical downsloping issues east of the mountains we’ve dealt with a lot this winter.. so we’ll see. As progged it’s a pretty strong system for a clipper, and it looks to usher in another reinforcing shot of arctic air.

Friday morning was the only morning I ended up below zero here (-3 or -4ºF), I got to exactly 0.0ºF last night. Light influences from the developing coastal in the form of light wind and cloudcover as you mentioned likely kept things from fully decoupling. Still been a heck of a cold stretch, when the temps likely fail to reach 20ºF again here today that will break the longest streak of days under 20ºF for KAOO that goes back to 1948 for that station. That was 7 consecutive days set in Feb 1979, and today will make the 8th day. The lows in western PA the last few nights have been wild where there has been ideal radiational cooling conditions. For official ASOS stations, the coldest I saw for last night was -20ºF north of Pittsburgh at Zelionople Municipal Airport (KPJC).

Been bouncing between -2 and -3ºF this morning here. Temperatures especially in the west and central this morning have ended up pretty close to the modeled temps of the coldest models (Euro/GFS). On the Mesowest network there’s several stations reporting -20 or colder, with a -28 near Slippery Rock. On the Ambient network there’s a -22ºF in the Barrens region SW of State College, a typical optimal radiational cooling spot. Temperatures tonight will likely be even colder overall with more widespread below zero lows.

I just think the phase happens too late, its hard to bring a later developing coastal low off the Carolina coast back in close enough to affect central PA without some kind of a situation where its completely cut off/blocked downstream.. which doesn’t look to be the situation here. The storm deepens rapidly and may retro a bit but then it shoots NE. New Euros doing some kind of dumbbelling type action with the low, which acts to really drive up its snow solution in southern New England. Cold’s probably playing a hand in it too, we’re in a frigid pattern. We’re looking at the potential for some record lows Saturday morning as this storm is just beginning to take shape. The center of the closed 500mb low is all way down over Savannah, GA as the trough rotates negative. That’s a bit too far down for us, the surface low explodes on the Gulf Stream and will likely run up along it.

The only thing really keeping me into this threat to any degree is the 500mb ridge axis in great positioning for C-PA. Otherwise it just looks like the trough is going to swing negative too late and system stays relatively progressive. Looked a little bit further into the CIPS analog stuff and off GFS guidance one of the top analogs for the Northeast/East Coast domain that come up is the Boxing Day 2010 storm, which I think is most the representative analog vs forecast setup of a top 5 that consisted of Jan 2016 and even Jan 1996. That’s why the 90th percentile is off the hook on that analysis. Statistically, those accumulations represent amounts that are higher than 90%+ of the dataset.. the highest outliers in other words. Having those big hitters in the mix also skews the mean as well. Here’s the median snowfall, which indicates a lot of these analogs didn’t produce much of anything. Here’s the mean 500mb vs GFS The mean western ridge axis on the analogs is actually a tad east of what the GFS has, and it’s definitely west of the alignment for the Boxing Day 2010 storm. That storm actually tracked up from the Carolina coast and inside of the benchmark while the general consensus of guidance right now is to take the surface low up from Hatteras outside (southeast) of the benchmark. So I think this certainly has room to trend snowfall back our direction, but I’m fairly doubtful it’ll be enough for C-PA due to the reasons mentioned at the top of the post. The storm gets going too late.

At least we didn’t see this kind of crazy sleet. https://www.wboy.com/pendleton/watch-crews-use-excavators-to-clear-sleet-slides-in-west-virginia-mountains/ Pendleton County, WV

Looks like focus could be starting again on about this time next weekend once everyone rests up haha. The 0z Euro op blasted central and eastern PA tonight. This amplifcation and major, highly anomalous closed 500mb low is notable on all the major ops, but the Euro’s the only one that had this kind of storm solution tonight. 500mb ridge axis out west is lining up in the spot favorable for a coastal to strike C-PA if we can time a phase. So we’ll see what happens with this, plenty of time to reel it in.