MAG5035

These heavier squalls moving through the central counties right now are probably going to make it to Harrisburg and deeper into the LSV the next couple hours with the best daytime heating likely maintaining them. Look for them to have grapuel and snow pellets in them as well with the sun heating surface temps into the 40s.

Amazing to see a full fledged snow squall briefly whiten the ground at 1 in the afternoon on May 9th.

Speaking of cruel, the deck and the car tops are already froze over here. That's going to be a long time we're below freezing here (probably 10-12hrs).

I'd say judging by the radar your currently at your best opportunity to see a mix or changeover with the remaining synoptic precip.

The situation 4 miles away at about 2500’. It’s 29°F up there. Looked like about an inch or so.

A steady light to moderate snow driven sideways on a stiff wind, no accumulation. It's definitely a weird sight with the freshly leafed out trees in town here as a backdrop. Temp already back to 35.

Might see some flakes in parts of the LSV but I think the NW flow drawing the cold into PA and undercutting the back side of the precip shield is going to limit seeing too much east of the mountains because of the downsloping component. Although the surface low getting going on the coast may help a bit keeping some precip around.

Nope this is just the Radarscope app. It's a one time $9.99 app but it's def worth it. It has all the dual pol products, different tilts, shows mPing obs, watch/warning products, etc. It also has additional subscription tiers now that you can get lightning data, archived and longer radar loops, spc outlooks, and local storm reports on as well. I just have the base one and use it on my phone and laptop.

Here's the downslope shadow on the radar, the dashed line is roughly where the Allegheny Front is. The mPing snow report in Altoona is mine. I'll probably eventually make a drive up to the top of the mountain this evening.

My mom was going to get flowers last weekend and decided not to go that day. I promptly told her she better wait til after Mother's Day.

Annd we have flipped to snow here... that quick. It's light though, the downsloping just off the Laurels is evident on the radar.

Black ice is a definite threat later this evening with the gusty winds and the rapid temp drops, especially in the central counties but everyones probably going under 32 tonight. It's looking to bottom out at 25ºF here, which is really going to hurt sensitive stuff.

Snow reports on the mPing obs down into Cambria County now, snow on the ground on the 511pa cam on top of the mountain above Clearfield (I-80 Exit 111). That temp drop in western PA is pretty wild to see. Already freezing in Dubois and Pittsburgh metro is in the mid 30s. Still rain here but the winds have kicked up pretty good so temps are likely to start falling soon.

It’s kind of misleading they announced that when they’re set to announce the next batch of counties today that will be going to yellow. And the way the news sources titled it, it’s really misleading. I guess I didn’t realize the previous state-wide stay at home was to expire today. They’re basically extending that out for the red counties but they will still be evaluating counties that can move to yellow. There’s not really any change from how they’re running their phased reopening plan, which looks to be evaluating counties on a weekly basis.

The synoptic event def doesn't look as good as it did. The system's timing overall is a bit faster by about 3-6 hours and the low seems a tad north and a bit later with getting going. Pretty much the snowy NAM is looking more like what the Euro has been looking like as the Euro has been the least enthused with wintry precip in PA. Also haven't seen an overly strong signal on ensembles other than maybe the SREF. So I think the changeover to snow is looking like it's going to stay confined to higher ground. It's still going to be crazy cold first thing Saturday morning and still a chance of some pop up frozen showers in the afternoon.

I dunno if it's really all that strung out, the NAM looks like it's coming more into line with what the other models have been showing... having a bigger portion of the event rain especially outside of the high ground. Timing is important with this. If this stays slow enough, the main part of the event is late in the day into at least the first half of the night... taking away the sun part of the equation. You would need crazy rates in the middle of the day this time of the year, but toward dusk (after 18z) and nighttime you can start accumulating with more modest rates. We have the things on the playing field to make this happen, having such a cold airmass pressing in with this storm system passing under us. It's going to be interesting to see what happens. I definitely think the high ground is going to see at least a few inches, but the wild card is going to be if this actually gets to lower elevations or even the Sus Valley. This won't affect potential for showers/squalls on Saturday. The core of the mid-level cold will either directly target PA or pass just north depending on models on Saturday behind the system. GFS and NAM are taking it right through PA with sub 516 thicknesses.. which is insane. -40ºC 500 mb temperatures are generally not something seen over the US in May. PA gets into -20 to -22ºC temps at 700mb (10,000ft) and -10ºC 850 temps. Even the 925mb temps are well below freezing. I bet some of the higher Laurels and north central elevations never get above freezing during the day Saturday. But you put that really strong May sun and heat the surface with such cold air aloft and your going to get some stuff to pop up.

Anything frozen would go over to the 20-21 season after July 1st. To properly tally average annual snowfall, it's done over a 12 month period from July 1-June 30/31 so the annual snowfall total covers only one actual winter season.

I once thought as you do. Those last two winters I've tallied snow here in my signature at 54.6" and 52.2" are average winters at my location at the foot of the Laurels. The 16.2" is pretty much 30% of normal and the wall to wall futility was something i've never seen. I was completely over this winter by the beginning of March from a hitting the slopes standpoint as there was never a point this winter the local resorts had a period of even half decent conditions. But you know what? I'm all in on this possible debacle Friday night. It's not likely anything else going on right now is "normal" anyways lol. Plus a paste bomb may actually help insulate the vegetation some with low temps Sat morning in hard freeze territory (mid 20s) Sat morning back this way. Having a trace and having measurable are two different things. If the flakes are flyin in the air, that's a T for the day. Grapuel also counts as frozen precip too so a non or little accumulating grapuel shower would go down as a T as well... and that's definitely on the table Saturday in the LSV. Lancaster has probably never had a recorded measurable event in May but that 1977 event for instance may have given them at T. Either way, any frozen that deep into the LSV in May is extremely rare. I dunno if State College has anything like this but NWS Pittsburgh has a whole webpage of miscellaneous snowfall data for PIT going back to 1884. Their latest recorded snow was May 31, 1893 (T) and latest accumulation of snow was 0.5" on May 25, 1925.

Rain and mangled flakes currently.

I was just about to comment that I saw it falling on the 511pa camera at the Penfield/153 exit up there.

Lol 0z NAM doesn't have the really heavy amounts but it snows on the whole Sus Valley and gets flakes down to the I-95 corridor in central VA.

I'm not sure on definitive dates. I would imagine more stations than you might think have recorded a T in May, but as far as measurable? Aside from likely KJST and KBFD I don't know offhand who else. Any measurable more than a trace in the LSV is likely uncharted territory in at least the last several decades. As far as may snowstorms, May 9-10, 1977 apparently had one in Upstate New York and southern New England. https://www.boston.com/weather/weather/2016/05/09/on-this-day-in-1977-the-weather-was-bad-as-in-13-inches-of-snow-in-worcester-bad

Hah 18z NAM must think so. That's not even done at 84 hours. Welcome to happy hour in May I guess.

The difference between the Euro and GFS for the weekend comes down a choice between insane and more insane. The GFS has been dumping the core of the 500mb PV right over PA while the Euro has been swinging it through NY State. Going to be crazy cold for mid-May either way, but the difference would be the core of the 500mb would provide the best instability for the rain/snow/grapuel showers that are sure to develop with daytime heating. The 500mb air at the core of the PV is progged at -40ºC, which I'm not sure if that is some kind of record over this part of the US but it's def not often you see air at that level that cold even in the winter. I'm pretty sure it would be the coldest ever observed in May over the northeastern US. Gonna have the watch the coastal wave later Friday too, the sharper GFS has the low going more underneath and has what looks like a bit stronger of a system. Would likely make a potentially more snowy scenario in the higher elevations of western and possibly even central PA with that 500mb low dropping. The system is also timed later Friday into Sat evening so it would take the strong sun out of the equation. A wet snow bomb is def on the table in the higher ground. Either in interior PA and/or upstate NY.

I think we're likely going to come out of this after mid-month, as modeling seems to flatten the trough and eventually show some ridging in the east and a bit of a western trough. Given how late in the spring we're going to be by that point, this is definitely looking like a candidate for straight to summer when the pattern breaks down and/or reverses. Saturday is going to be the low point for this whole thing though as an unbelievably cold airmass for this time of the year drops pretty much through PA. Like I said yesterday, the 1000-500 thicknesses are insane and something I've never seen in PA in May.. with the GFS easily sub 522 over all of PA and Euro sub 516 over a big portion of the state. Let me put it this way, if we had thicknesses like that in the middle of January we'd be concerned about it being too cold and supresssing the storm track. Or another way, if this type of thing actually dropped down in the middle of winter the thicknesses would be much lower than that (probably a 2015 style cold outbreak). That's generally not achievable well into May at the low levels, but the mid level temps are what's driving such low thickness values. When the core of this 500mb low moves through PA Saturday, models are progging nearly -40ºC (!!) at 500mb, -20ºC at 700mb, and -5 to -10ºC at 850mb over all of PA. That's crazy this time of the year. GFS generates a couple hundred j/kg of CAPE (Euro a bit north) Sat afternoon. The May sun is going to heat surface temps into the 40s or maybe even 50 or so in the LSV, so probably don't need to tell you the potential is there for robust diurnally driven showers with how cold it is aloft. I think anywhere in the region could see frozen on Saturday, either in grapuel or snow (or both). Grapuel counts as frozen precip too. It's going to be so cold aloft that a heavier shower is going to overwhelm the lower part of the column, and you'd only have to go up to about the 925-900mb level to get below freezing. The higher ground of west central and north-central PA could see two separate snow events in addition to this with tomorrow's system as well as a system progged on the models that ejects east later Friday underneath the pressing anomalous 500 low.