MAG5035

Starting to flirt with the mixing zone on the CC product. Still all snow for now but will see when the next patch of brighter echoes get here shortly. HRRR has been pretty consistent on an approx 11pm transition to sleet here so that’s probably looking pretty good. Also starting to get near the dry slot as well, though I expect some rebuilding of echoes to a degree.

Gorgeous storm

Right around the 4” mark now, with moderate to heavy continuing. Temp has been rising but still in the teens (19.4ºF), Pressure down to 1002mb.

One thing I’m noticing on the meso surface obs is that most ASOS stations have winds of a NE component to them in central/eastern PA, and even all the way down in all of Sterling’s CWA. So that’s likely to at least hold some surface cold for awhile. Sleet will probably be a more predominant mix type for a while after transistion as it will take some time to modify 925mb.

M 2.4”, Heavy snow. Temp has torched to 14.2ºF lol. Wind NNE 5 G 8, Pressure 1007mb

I was past the first inch when I measured about 20min ago. Heavy snow, 13.1°F(!!)/ 10.8°F This is the coldest synoptic event I’ve seen in years

Snow has begun here in the last 15-20min with a dusting. 16.5ºF/2.8ºF

Yea I”m not sure, could be a difference in whatever algorithms they use to generate the p-type too. Because WeatherBell’s winter conditional QPF are all separated now, there isn’t anything lumped with snow accumulation.

Yea being 7 years old that’s right when those WB maps/products first came out. Early on they were known to be really exaggerated on the edges where there was mix like the Tropical Tidbits maps are. TT literally says on their accumulation maps total snow/sleet. But WB changed their algorithms at some point and are a good bit better and I consider it fairly reliable. Gotta remember type of models make a difference too. A global model like the Euro/GFS aren’t going to see the finer details and sharpness with these transition areas. But any rate on Weatherbell all p-types are separated now. if I want a sleet map, I can pull one up. They calculate accum for sleet on a 3:1 ratio for most of the models. Euro has been colder thermally and has had a more of a straight snow-rain transition with little in between in PA. Here’s the 3k NAM’s sleet map.

Current obs: Clouded up here. It’ll be interesting to watch the wind and barometer as this storm comes up tonight/tomorrow. Also still pretty dry here with the dew point below zero.

I did follow @canderson ‘s scientific advice last night and install my weather station outside lol. So currently I got a 16.3ºF temp and a 1.3ºF dewpoint. Should be interesting to see how low it goes tonight. Only got to 19ºF for a high.

Haha yea there are some large valleys in that region and that’s where most of the population resides too. Although on the other hand, this is the general area I expect the potential stripe of freezing rain that’s more than just a glaze to a tenth. I”m on board with their forecast numberwise (they put a new map out) and a bit of a reduction in accums. I just think the overall high storm impact and still a good bit of overall model support for 6”+ justified a warning for some more of the central counties. Gotta draw the line somewhere I guess. I still expect to get to 6” in AOO/UNV with the amount of mixing dictating the top end potential.

The stable cold boundary layer at the surface usually keeps higher winds from mixing down that far away from the coast. You would need some kind of convective element otherwise, which is possible I guess given the dynamics of the system. There could be some kind of a line denoting the occluded front right before the dry slot. That’s likely the only time I could see noteworthy gusts prior to the low passage outside of maybe some gusty winds on some of those eastern/northeastern ridges. Post low passage though? It is definitely going to be windy probably region wide. The Laurel’s might have worse conditions later Monday than during the main synoptic portion with blowing/drifting and some lingering upslope snows.

So the majority of Bedford County gets 6-11” and 1 tenth of ice warning while Blair (Altoona) and Centre (State College) have an advisory for 3-5” and 1 tenth of ice? All while my newish grid forecast has 6-12” total. That makes zero sense lol. My overall take on the afternoon guidance led me to thinking the warning swath would have looked something like this.

Lol I don’t think I’ve ever seen that lineup of counties with Bedford tacked on before without including the other I-99 corridor counties. They must be concocting a different warning statement for them haha.

Its been a pretty common theme with this storm reaching the point of being a mature cyclone when the low center approaches our latitude. This low rapidly deepens going through the Mid-Atlantic region which gives it the look of bending back in as it occludes. I don’t really have much to add that I haven’t mentioned before, the overall storm track continues to be the issue for the LSV. I still think the warm surge is brief but as I mentioned before the key is going to be the strength/speed of warm air intrusion aloft on a strong low level jet before the surface low runs over some portion of eastern PA. Can the LSV get smacked with a good front end snow before warm air wins out for a time ? Certainly, I think most guidance suggests a period of decent snow up front… but it’s looking more of the advisory variety (general 2-4 maybe some 5” in the western part of the Sus Valley, IMO. I agree with @MillvilleWxon his take about the Euro, although I have liked it’s overall interpretation of a tighter transition zone. I still don’t buy a super wide swath of measurable ZR in our region with this setup. Certainly in the south its a different story, but as mentioned before the high pressure moves east as the storm makes the turn up and it becomes a boundary driven/cold conveyor belt setup over the initial CAD setup. I see any ZR swath as thinner as I think only the LSV gets 925 and surface routed. And even though the low is close I do not see the ridge and valley region westward getting those levels routed. 850mb might though, so sleet could be more in play there for a period of time. If this ends up colder and we don’t have a quicker transition to liquid/freezing liquid, the dry slot might shut off precip before there’s much QPF as non frozen. Which speaking of… The other issue, which you could argue is the bigger one in the longer run is the dry slot. Eastern PA is going to slot out with the forecast track and how much that slot gets into the central counties (the UNV/AOO/99 corridor) will factor into what the top end is there. The storm rockets right up, it’s not blocked due east or a cutoff slow mover.. so I don’t foresee a part two snow for the Sus Valley like some of the recent bigger events when everyone gets back to a snow column by Monday morning. The deform will hang in western and perhaps some of central (another thing to consider in the central region with top end)

This is now pretty much fully in the range of the 60hr 3k NAM so the 12k one is dead to me lol. It’s a least a bit closer to the rest of the guidance.

Euro still doin it’s thing for the most part. 0z vs 18z

In the meantime I’m trying not to sweat the models too much. I finally will have an actual weather station for obs once I get it mounted and set up. (No, I don’t have anything on tap at the moment lol)

Lol, definitely not. It’s not much different than it’s 18z but it ramped totals up in western PA and edged them back up a tad in the central. Sus Valley was still about the same.

Sigh, this freakin NAM. Like the literal definition of a turd in the punch bowl lol. I will say the 3k NAM looks better than the 12k, at least that roughly gets the 2” line to the Susky.

Despite all that it still looked better p-type wise at 48hr on approach than the 18z NAM lol.

Yea, if this does go to liquid at some point in the storm it probably will be with surface temps right at or above freezing. That’s part of the problem with the low tracking inside into eastern PA. The low level flow is ESE and those gusty winds will moderate the surface temps, esp after p-types transition. If this found a way to even mostly stay under PA and go towards Philly or NJ you could have a more ENE flow which could hold the low level temps better. The NAM may be onto something with quicker warmth aloft but it maybe too overzealous with its super strong and far reaching 850 jet. That feature is going to be the key with the front end. The other part of the problem which has been modeled for days is the surface high setting this cold air mass slides east as the storm tracks up. This transitions initial CAD into a boundary situation where the track of the low will dictate the swath of heavy snowfall and transition zone. If this thing tracked NE right up just inside the coastline the high positioning east wouldn’t be an issue as there is still plenty of cold wrapped into the system.

No way up there in P-burg, I’ll happily take that stand and go down in flames if need be lol. Some kind of period of sleet is definitely a real possibility though and maybe freezing drizzle if we slot this far back. I’m still pretty confident in mainly frozen (snow and/or sleet) in this general area here. The low would have to literally track over us or in western PA for me to change my thinking.

I do feel the same way, but I don’t completely discount the NAM’s robust warming higher up near the 850mb level either. But same stuff as 12z. The money 3hr frames for ZR are 60 and 63. Using my nearest station at KAOO as an example since I’m in the thick of the heavy ZR over here. HR 60: Surface -6ºC, 925mb (~3k ft) -6ºC, 850mb +2ºC HR 63: Surface -2ºC, 925mb -3ºC. 850mb back to 0ºC Even with that basic breakdown at the major layers I look at that and ask what part of that suggests that particular station sees 0.78” as freezing rain? I think something toward a NAM scenario might get a few hours of sleet into the central and *maybe* western counties. But Pitt’s advantage is the 850 low tracks favorably on the NAM for western (and serviceable to central counties) plus overall flow is on the cold conveyor belt side of the low. We don’t have an Ohio Valley low with SW flow intruding in this situation and trying to overcome that with a secondary to the coast. The warm advection comes from the tremendous easterly flow aloft with the coastal low. I can’t really think of a situation in the past that has presented the NAM type scenario of that much mix/ZR into western PA so that would be a new one to me if it happened.