MAG5035

I did just that not too long ago, it definitely didn’t disappoint haha. It really sticks out with the clear skies today, I wish I could load the full quality pics on here. It’s always wild the difference 4 miles and 1100’ of elevation makes. Top of Wopsononock Mtn west of Altoona

This looks like a quick hitting advisory type event, like a 2-3" scattered 4" type deal for most with perhaps more frequent higher amounts (4-6") a better possibility in the Laurels, I-80 corridor, and Poconos. Also need to consider the possibility of a weak spot in the south central counties between I-99 and I-81 (Bedford, Fulton, Franklin, maybe southern half of Huntingdon, etc.) where could only be a 1-2" type snowfall. Low stays NW of PA on a general westerly flow so that typically invites the probability of some downsloping in that aforementioned area, and it has been showing up on most model guidance. Could only be 1-2" in the LSV as well, and I'll explain that below. Timing and temps are another concern, esp LSV below the turnpike. This appears to be a late morning to late afternoon/early evening hit, so rates better be good there with marginal low level/surface temps. I often find that after about the 2nd week of February or so it's like flipping a switch with respect to solar input (ie the sun angle)...not yet with heavier and/or cold storms, but with clear days and light events with marginal temps (specifically ones in the middle of the day). NAM once again the warmest, bringing mixed up into the LSV. Showing ZR as primary p-type but I would imagine any icing would be limited in scope if it were in fact liquid precip. And considering how thermals have went in the other two events this past week (even though the M/D simultaneously got their 4-6" of snow and still had mixing all the way up through MDT with Thur), I'm inclined to seriously consider the NAM in that regard. So ideally, a good shot of heavy precip up front would at least secure getting a couple of inches. Ratios might be <10:1 as well. Kuchera maps have actually looked a bit worse than the 10:1 maps, and while Kuchera method applies a fairly simple algorithm for calculating the ratios it is generally picking up that the temps 850mb to surface are a bit marginal.

That looks like a lot of snow down there too at that elevation. Yea it was a combination of rime ice near the summit which is in clouds a good bit (over 3100' at the top) but alot of it was also the new snow sticking directly to the iced trees too. It looked like they had a significant amount of ice up there from that ice storm even for their standards, and since there was never any strong warm push at what is essentially the 925mb level at the top of the mountain there, most of it didn't melt.

I went up to Blue Knob in the afternoon/evening yesterday and it was quite a sight up there. Probably a general 2’+ natural snowpack around the mountain plus the 1/2”+ of freezing rain from the ice storm and rime ice (esp above ~2600ft) that never melted before it snowed again the last couple days.

Decent burst of snow currently. Wouldn’t say it’s been piling up by any means but it has been snowing pretty much all night so far. Up to 1” additional now with round two, though that’s the running total all the way since mid afternoon.

It does seem like the stuff around is being somewhat under represented on the HRRR but it's still fairly patchy so I don't think we'll end up with as much as some of the models have tonight. I think for the most part an inch or less but perhaps we can get a band setup that drops some localized 1-2" amounts. The best action seems to be staying NW of I-81 for now as well, with it actually snowing half decently here currently. It's been snowing off and on enough this evening that it's got most of the streets and secondary rds icy again. Board was cleared this afternoon right after it started snowing off and on after 2pm. 2.9" fell before, and just measured 0.7" so far since for 3.6" on the event. That makes a 44.1" current season total on those measurements. I generally consider the 45-55" range as average-ish for this end of Altoona right against the Allegheny Front so looking pretty good for Feb 18th.

Some steady snow trying to get restarted back this way. While I was out clearing stuff off a bit ago I had a bout of freezing drizzle that promptly glazed the car right after I brushed it off.

2.8” and slotted out over here currently. Hopefully can get things started back up this afternoon.

2.1” for my last measurement til morning. Steady light snow, 23°F

Moderate snow and 24ºF. Midnight measurement is 1.3" of straight powder snow in a bit under 2 hrs since it got going. Not too bad considering the near term stuff late this afternoon and early evening didn't have this even starting here until about now or a bit later.

Much better flakes now and moderate-heavy rate. Binocular check of the snowboard with the flood light on already looks like over a half inch.

Yep same over here, a nice moderate pixie dust snow for now. Getting this early swath of snow to set over the area is gonna be a big part of hopefully getting pretty well into our forecast range of the advisory (3-7"). I think we're in pretty good shape. There's a patch of some more enhanced echoes on radar over JST that should try to shift this way here within the next hour or so.

Flurries starting here, 25ºF.

Great catch. And the 0z sounding (weather balloon) is hard data too. This was my worry about the southern tier in terms of a getting a warm layer somewhere in between 850-700mb. Yea it will wet bulb down, but more robust WAA there is already being noted. Fortunately for our region I think this has been trending towards minimizing the threat for sleet/mixed (0z NAM didn't have it getting very far across the mason-dixon). But there's still a decent possibility of pingers at some point to consider in likely the bottom tier of LSV counties.

To clarify a bit, holy crap the NAM is sleeting on DC. 2.5-3"+ on both the NAMs lol.

Boy I bet the DC metro folks are loving seeing the 0z NAM and some of the differences between other models this close to game time (||GFS vs GFS and Euro). 3k gives them almost nothing snowy and 12k NAM isn't much better and the 0z HRRR hits them good. My only worry for this region is some sleet mixing in at some point for a little bit in the southern counties. At least none of us are riding THAT edge for this event.

Got some echoes overhead, just waiting for it to hit the ground.

I don't know if it's necessarily a Nina thing. Models being too high with QPF certainly isn't anything new.. especially on the high resolution short range stuff like the NAM and also the RGEM at times too. Pattern is progressive but we're also not phasing shortwaves or amplifying a big time low here in this alignment, and that's a good thing with where that 500mb trough is postioned currently with no NAO/AO blocking anymore. That's why the overrunning aspect of this wave is probably going to be the main part of the storm with the weak surface low and weak mid-level features. We've had a few of these type events this year too.

A big key to what we're going to see snow wise with this system is what happens right up front late tonight into early tomorrow with that finger of early warm advection snows that develops and where it's placed as that probably will be the best snows ratio wise and could throw a stripe of a few inches right off the bat to whoever gets it.That's really been the name of the game with this system since last week, what it does on the front end... even with it being a much colder system overall than it was looking at that point. At any rate, it seemed like a good bit of guidance today (especially the short term and high res stuff) places this early stuff closer to a JST-UNV-IPT line than say a Cumberland to MDT one and then the main surge of precip fills in the rest where it will probably be heavier overall in the southern tier. This is actually most important for that corridor (JST/UNV/IPT/FIG) because this may be a low end advisory or worse without it in the central counties. I'd wager the folks that gets a good piece of the early stuff and transitions into the main surge without wasting a period of light or non-consequential rates are probably going to be the ones that see the best accumulations for the whole event. And if that actually does end up back as far as that JST-IPT corridor, I'd def be more worried about the implications of eventual mixing in the LSV counties. NAM and related near term guidance is the mixiest still, while generally everything else minimizes the mixing above the mason-dixon line. Still have the same concerns with the 500mb mean trough centered west over the central US as well as the mid-level features west of PA and associated WAA busting 0ºC somewhere in that 850-700 layer in esp the LSV. The trend the last couple days has been a bit of a SE shift in the heavy swath and especially an overall toning down on QPF. I think this is basically a 4-8" for all the regulars in here. Clearfield and Williamsport should eventually at least get to 3-4" by the end of this event. Places like AOO/UNV 5-6" and the best chance of a consistent 6"+ swath likely resides closer to the turnpike. Below the turnpike in the southern tier/LSV has the best QPF for widespread 6"+ but that directly depends on if the mixing happens. If it does, I still think everyone gets 3-4". The upper end of this is probably 10".

Yea this wasn't really looking like much more than a 6-12" type event at any point in the heavy axis, other than like the 18z NAM. Another thing I didn't mention on my long post earlier going over the mid-level lows was that we're not really deepening the coastal storm. It's just an overrunning wave attacking a cold high pressure with overrunning WAA precip in either one or two separate heavier precip areas depending on the model. And the weak 850mb low never goes to the coast nor strengthens much, with the parent low staying west of here. So you don't develop the anomalous easterly flow you want to look for to start getting the widespread big amounts and intense banding.

Temps already back to 24°F here with some fluffy upslope snow showers starting to get things covered up again. Spent enough time above freezing this morning that ice is mostly off the trees. Was hard to measure. I called it about a half inch of sleet which combined with the freezing rain made quite the ice layer on the snow. Actual ice accrual on trees and such looked fairly similar to the mostly ZR event I got at the end of December (which I measured 0.2”). Snowpack avg depth after the ice is about 8-9” with as low as 4” and as high as over a foot.

The bigger concern I have for especially the LSV wrt to some mixing later in the storm deals with the mid-level features at 850 and 700mb. The 850 low and 700.. trough are based west of the area. Fortunately these features are weak because a more dynamic phasing storm would assuredly be cutting west given 500mb positioning of the mean trough still over the middle of the country into Texas. Here's the 500mb mid-storm via the Euro. You wouldn't think at first glance CTP (or southern PA here in the Euro's case) is in the midst of getting a significant snowfall but thats the magic of when the features below 17k feet (500mb) are at least somewhat favorable and there's cold air. This isn't the first time we've played this game this winter either. Now going to show what the latest 3k NAM had with it's mid level features. The NAM is definitely on the most amped side of guidance, but same general idea is applying to the other guidance as well. 850mb heights/wind 850 temps First off, you can see the big difference between this one and the last storm... where the 50-60kt+ jet is nosed over SE VA and the Delmarva instead of right directly over PA like last night. There is some southerly flow into PA (enhanced a bit on the west side of the Laurel's) but not the major jet that torches the layer. That big arrow i drew doesn't show it well but the streamlines show that flow turning back a bit toward a due southerly flow over the Delmarva keeping the 0ºC line somewhat close. But overall, that level is okay for us but we don't want to slow down and amp this storm up much more or your going to direct that southerly flow more towards southern/southeast PA. Now 700mb winds/heights 700mb temps This is the level (and possibly somewhat between the 850 and 700mb) that I'm most concerned about for mixing here in our region. You can already see why the NAM has so much sleet as a pretty strong 700mb jet runs through the Mid-Atlantic into PA.. There's going to be some significant WAA in that layer either way (which could cap snow ratios to a degree) but that 0ºC line is teetering near the LSV at 48 when the bulk of the precip is happening. Above 0ºC 700mb air does work into roughly the SE quarter of PA by hr 54. Now as I said..the NAM is generally the most amped with the features I pointed out right now, but consider where we ended up last night. WAA aloft ended up being so strong that even the counties in the north that we're supposed to still 6+ of snow at the beginning of yesterday ended up not seeing anywhere near that. Now let me add the disclaimer that this event should drop some nice snow up front for everyone. With that said, obviously my concern is more robust warming aloft than even the NAM has modeled... especially at 700mb considering how far west the low feature is. You get that sneaky thin area up somewhere between 700-800mb of above 0ºC air and suddenly your pinging away. So def something to keep in consideration.

It's a pretty weak low pressure system overall that's trying to press up into what will be a much better positioned high pressure this go around. I don't think it's really fighting anything, it's actually more focused with a singular significant press of overrunning precip vs the Euro or the ||GFS which seems to have two separate surges of heavier precip. Euro op looked somewhat stronger with the high pressure so that likely had a hand in kind of focusing on the southern tier more. The surface "low" you see west of the mountains is part of the overall low pressure area but the colder denser air draining down via the high pressure in place gives it that two low look. This is an A with a pretty weak surface low. Classic overrunning look.

Here's the sleet total map, good lord lol.

Pretty close. MDT is getting 14.1 Kuchera on 1.36" QPF.. so basically a 10.4 to 1 avg snow ratio.