MAG5035

Past the 9” mark now with continued heavy snow rates and temps have torched up to 10ºF. 

16 minutes ago, Blizzard of 93 said:

What do you those radar trends could mean for the Harrisburg area this afternoon?

Back in western PA the mix line is remaining well south of Pittsburgh, generally near the Mason-Dixon line. That then cuts up NE thru Bedford/Fulton to where it’s pressed up into the Sus Valley.

The next couple hours are going to be where the max WAA occurs to drive the sleet up into the Sus Valley. I would expect a changeover back to snow to try to work back down thru the LSV eventually as that intense WAA passes and the column starts cooling at that level. However, the big thing by that point is going to be the race between that and the main precip shutting off. Models seem to be timing a mid-evening shutoff (10pm ish). There’s a lot of storm to go. 

10 minutes ago, mitchnick said:

This sleet is different from most sleet fests. One of the mets in the MA forum commented that there are still a lot of needles with the sleet and opined could be crystalline below the 700-750mb warm layer. It definitely looks different. 

Thats certainly possible, That 700-800mb area is the only part of the column that warms to the point of mixing and that’s quite high up. We never lose 850mb on down, and there’s plenty of lift at that level as well. 

Heaviest snow of the event so far, working on 7”. Temp 9ºF 

Past the 4” mark here with moderate to heavy rates. Temp 8ºF

The first heavier band has arrived and it is ripping here..probably working on an inch or so already. Decent flake size and it’s fluff. Temp is down to 9ºF, which is nuts for an event like this. 

8 minutes ago, Ruin said:

Ah wow I just clicked updated forecast now says 6 to 8 lol

In Harrisburg? 

Surprised no one posted this earlier, CTP bumped up amounts areawide. My point and click is up to 13-21 inches now. 

Snow began here just a bit after midnight, light for now. Temp 10ºF, Dewpoint 2ºF. Its happening! 

3k NAM does try to bring the snow line back down as the secondary starts to take over, which keeps places like JST and AOO pretty much mostly or all snow but it slots before it really drops back into the Sus Valley. At the same time this model is showing the best comma head over western and northern PA and is probably the snowiest run yet for the max snows, which is exceeding 20” on Kuchera in west central PA. 

Sleet is prolific in the far PA southern tier/LSV and well,  just about everywhere else south of there. This is the kind of setup I feel there’s going to be a zone of multiple inches of sleet somewhere given the depth of the arctic air mass. That widespread? We’ll see. But that’s 2-3” of sleet on top of the 5-7” of snow it puts out in the LSV. 

Snowfall

1st and probably only call I’m gonna do with this. I could’ve just put a text box that said 10-18” on it and called it a day and would’ve had the model support to defend it. But I am hedging some on the NAM thermals being at least partly right and a bit more sleet intrusion. Not full NAM, but somewhere in between that and the general consensus. 

These are purely snow numbers, obviously the reduced zones in the southern tier are for sleet mixing, but if that were to occur than sleet accumulations would be fairly notable as well (perhaps an inch or so). The only reason I’m giving the NAM a bit more weight in what is mainly a snowier consensus is strictly its handling of mid-level features and the warm nose. If the snowier consensus wins out, then the whole subforum simply sees 12-18”. Impact wise, that really isn’t that much of a difference.. this is going to be disruptive. 

I also think top end will be tempered a bit, mainly for speed of the system. Mostly I think there will be a lot of 14s and 15s with some 16-18” reports sprinkled in. It doesn’t look like any kind of a comma head lingers in C-PA to drive widespread amounts toward the 20” mark. What could overcome that is a fast start to the heavier snows when the best snow ratios will be before the mid-levels of the column start to warm later in the event. Both of these points were mentioned in CTP’s disco from yesterday.. which was a good informative discussion. 

Oh yea here’s some current obs, it’s half a degree here right now. 

55 minutes ago, Blizzard92 said:

Obviously much higher QPF event back in 2007, but does anyone recall the breakdown of pure sleet (vs. snow / freezing rain) accumulation in the Valentine's Day storm across the LSV?

Back this way the PSU Walker Building noted 5.8” of snow and 2.8” of sleet on the observation card from that event, and then a further 1.8” of snow on the next day’s observation card. I do remember this storm made quite the glacier pack. 

12 minutes ago, Itstrainingtime said:

I'll look when I get home next weekend but I vividly remember measuring 4.1" of sleet in Maytown.

That’s about what the 3k NAM puts out for a large chunk of Virginia into the western Carolinas. Despite getting the mixing further north, it is by no means warm outside of that region near the 800mb level where above freezing air manages to advect in. 

Which actually brings up the haggling over details that I’m usually trying to sort out for our area, ice impacts. Let’s look down in the Mid-Atlantic region…I’m no fan of whatever algorithm the Euro uses to generate its p-types when it comes to sleet vs freezing rain. Instead of a sleet bomb, it pretty much encases the entire state of Virginia in about .75-1.00” of freezing rain. These two models have a pretty similar column thermally. 

Here’s Euro’s 925mb (3000 ft temps) 

Euro 1hr precip/ptype at the same frame

That’s with surface temps in the low to mid 20s all the way down thru western NC and 850mb (5000ft) temps below zero in northern VA. No way am I buying that big of an expanse of crippling freezing rain on CAD of that strength and depth there outside of the Apps in the far western part of the state. A much more sleet heavy scenario, with an eventual transition to freezing rain late in the event seems more plausible. But yea those are two models with radically different ice scenarios despite similar column thermals.

Applying this to our area, any mix type during the main part of this is going to be sleet. There’s just too much depth to the cold for anything appreciable freezing rain wise.

1 minute ago, SnowPlowGuy88 said:

I was hoping for a nice long duration, high total event. Went from going in early Sunday morning to thinking I can get away with coming in around lunchtime. Just thought with 24+hours of snow that 18-24 was approachable. This is a thankless job/hobby. Glad to only have one site to worry about vs the previous 8-12 I had to deal with at my other employer. Stakes aren’t as high now, but I do want the big one. So much fun

This storm has definitely sped up a bit both in onset time and ending time now that we’re getting into the near term forecasting of it, which is pretty common with these type of storms. It looks like the business end of this occurs in a bit under 24 hours now, arriving in the LSV approx 2-3am Sunday and starting to shut off midnight-1am or so Monday. 

3 hours ago, canderson said:

@MAG5035 - you going to do a map? It’s been a long while! 

I might do one. Think I at least want to see what the 0z suite offers up first. 

Now that this is finally into 3k NAM range we can have a look at the sounding to see what we’re dealing with in terms of warm air intrusion aloft. 

Sounding for LNS (Lancaster) at hour 56

As you can see, the warm air intrusion is pretty high, situated between the 850mb and 700mb layer. That’s why at first glance the 850 and 700 mb temp maps might look okay for an all snow column. Could it be too aggressive with the WAA at that level? Sure, but I’ll forewarn that this was the exact situation that sunk the significant snow in a lot of NE PA back on 12/26. NAM was about the only thing that caught that. And it doesn’t matter how cold it is at the surface. When you melt a falling a snowflake it doesn’t turn back into a snowflake when it refreezes. 

This is a different storm setup to be sure, and again.. there will be significant snows before any mixing where it happens. And sleet will be the predominant mix type given strength and depth of the arctic air mass. 

7 minutes ago, canderson said:

Altoona’s never won anything, ever. 

Lol, certainly not in the 20”+ inch snowstorm department. It’s been since probably 1994 that one of those has happened here in the city itself. ‘96, ‘03, and ‘10 were all 16-18” events and Jan 2016, Dec 2020, and Feb 2021 were about a foot. 

GFS did get a tad NW with the snow/sleet line compared to its 18z run, getting into a portion of Lancaster and maybe extreme southern York. Still a plenty big enough hit for everyone. Top end down a slight bit area-wide, basically 18-19” (Kuchera) for everyone. 

51 minutes ago, GrandmasterB said:

Here's what I have so far.  Pretty aggressive with the lowest total being 12.8 outside of my brilliant hedge against a nightmare scenario:

User	Prediction
canderson	12.8
2001kx	14.5
nut	13.9
Festus	17
Bud Bundy	8.2
SnowPlowGuy88	22
MJS	15.5
Yardstick goes somewhere	19.3
Jns	17.5
Carlisle	19.59
paweather	16
pawatch	16.4

 

I’m really torn between going with what I think or going low because it hasn’t been an official winter in here yet without the annual hotly debated lowball snow total measured at MDT.  I’ll go 15.0”

1 hour ago, canderson said:

The nam is really pumping warmth into the 700mb layer. I call its bluff. 

It has deeper mid level features that are further NW, particularly at 700mb..which is why the WAA at/near that level is so strong. It’s a viable scenario, the 12/26 storm is definitely on my mind here when it comes to the NAM but we’re not yet at the range that it even covers the whole storm so I’m not going to get wound up about it but I’m certainly going to see what other guidance does in the meantime. For all of us here this is likely a sleet vs snow scenario if there ends up being a mix type. Column probably holds the whole way up to about 800mb in a mixing scenario and the frigid surface temps probably aren’t going anywhere. 

Another thing to consider is if we hold all or mostly snow in the southern half of the state, there is still gonna be a good bit of WAA in the mid levels. If we end up somewhere in the spectrum between the GFS and the NAM that  could eventually affect snow growth later in the event at the levels where some of the best lift will be and hence you end up with worse snow ratios even with how cold the surface will be. Kuchera only calculates off of the coldest temp in the layer and not the combo of where the best lift vs temp of that level is. So a 17-18:1 fluff bomb could turn into more of a standard climo 12-14:1 during some of the best part of the storm. 

Just laying out thoughts here, I’m pretty highly confident everyone easily gets warning snow in here and impacts are going to be major regardless. I feel like a 10-16” type snowfall area wide is a fairly prudent call right now with the acknowledgment that this could trend a little bit worse (more sleet) in the southern tier or better for everyone if something like the colder GFS came to fruition. 

And wow, Winter storm watches up already for everywhere, literally. I don’t think I ever saw such a large expanse of watches.

Looking over the 0z ensembles, they continue to be more supportive of an all snow outcome in all of C-PA despite the Euro and especially Canadian op creeping that mix line into southern PA. 

Here’s the Canadian ensemble members and p-type. Note that none of the members really intrude into PA with the mix line. A couple get close, but snow is predominant regardless. That factors pretty heavily into what your seeing on the NBM maps, as it blends all these ensembles. 

0z Euro ensemble is fantastic

Here’s the multi-run trend for MDT (Euro ensemble), you can see how this has really escalated the last couple days. 

27 minutes ago, canderson said:

0z GFS is running and contains new data from the hurricane hunters. 

They can keep that data coming haha. It doesn’t get much better than that for a well timed and positioned handoff to the coastal low to put PA in the best snows. 

8 minutes ago, Blizzard of 93 said:

I think the NBM factors in ratios.

It does, I know reading into the updates of the new version that it mainly applies the Cobb method for snow ratios. I think the current version does to a degree as well, not sure. But the NBM snow maps do factor in variable ratios.