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Central PA - Winter 2021/2022


Bubbler86
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1 hour ago, Itstrainingtime said:

24 hours later, CTP isn't looking so bad for waiting to hoist advisories. 

haha...you read my mind.  I think at times we all take turns hating on CTP for the timeliness of their advisories/watches.  I know they have to follow certain guidelines dictated by the regional headquarters for their CWA.  If I remember correctly, in order for them to issue a watch in any particular county they have to have >70% certainty that at least 50% of the county warned will reach warning criteria.  Obviously it is much less strict with advisories.  I also know that if they believe a watch will be necessary, they can't issue it until the start time is closer than 36 hours away.  For this particular event, like MAG has said many times before, even if just a tiny bit of ice could affect roads and/or sidewalks, an advisory seems warranted to at least alert for the potential for the ice.  That isn't crying wolf, and I don't think the public would mind if the advisory was lifted closer to the event.

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56 minutes ago, Itstrainingtime said:

33/28 here now - I expect zero icing on roads in this area. Perhaps some glazing on trees and power lines for a few hours later tonight. I think you need to get up in the MSV until there's issues of significance. 

Not unexpected. 

I wouldn’t write off issues completely. Yea surface temps got a tad freezing today, they were supposed to. They should fall below freezing when precip arrives. Here’s what the 23z HRRR  just initialized 925mb (3000 ft) temps at. 

image.thumb.png.102e1c7bcbbc4a62ed1bd2af22f97f9f.png

They’re about 1 degree or so warmer at precip arrival around 4-5z. But yea -6 to -5ºC is about 21-23ºF. Pretty decent depth and strength of the low level cold, so that depth suggests to me sleet’s definitely in the equation the first couple hours all the way to the mason-dixon despite what p-type maps show. 

Here’s THV’s sounding generated from the HRRR at 05z (approximate precip arrival). The warm nose is elevated but easily notable, but the column is below freezing from 900mb (approx 4k feet) on down to the surface. 

image.thumb.png.5c8619f93132ea6ac6094e5f4b20e055.png

Otherwise I think CTP’s forecast/headlines are fine, though I probably would’ve considered a few more central/south like Centre, Huntingdon, Fulton, Franklin, for maybe a bit more freezing rain and less sleet. If 925-850 air advects in warmer/faster that could mean the I-80 counties also get 0.25”+ ice in exchange for a bit less sleet/snow. That’s definitely a distinct possibility as well.

I do think as noted by a few in here that QPF might be a thing in the LSV as noted on the newer NAM runs. If that’s the case, that’s probably a bigger limiting factor in higher ice totals than temps IMO. This isn’t Feb 3-4, the CAD is already locked in for most of the night with the precip attacking it. 

 

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I forgot to give my conditions...

Currently 31.6 degrees and hasn't budged for more than an hour.  Dew point is 22 degrees and the wet bulb has decreased slightly from earlier to 28.4.  That at least helps increase the chances that temps will cool off a bit more once good precip is underway.

Latest radar shows serious juice about to enter southwest PA.  Definitely will be interesting to see how much sleet we all might get and how quickly it changes to zr.

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5 minutes ago, MAG5035 said:

I wouldn’t write off issues completely. Yea surface temps got a tad freezing today, they were supposed to. They should fall below freezing when precip arrives. Here’s what the 23z HRRR  just initialized 925mb (3000 ft) temps at. 

image.thumb.png.102e1c7bcbbc4a62ed1bd2af22f97f9f.png

They’re about 1 degree or so warmer at precip arrival around 4-5z. But yea -6 to -5ºC is about 21-23ºF. Pretty decent depth and strength of the low level cold, so that depth suggests to me sleet’s definitely in the equation the first couple hours all the way to the mason-dixon despite what p-type maps show. 

Here’s THV’s sounding generated from the HRRR at 05z (approximate precip arrival). The warm nose is elevated but easily notable, but the column is below freezing from 900mb (approx 4k feet) on down to the surface. 

image.thumb.png.5c8619f93132ea6ac6094e5f4b20e055.png

Otherwise I think CTP’s forecast/headlines are fine, though I probably would’ve considered a few more central/south like Centre, Huntingdon, Fulton, Franklin, for maybe a bit more freezing rain and less sleet. If 925-850 air advects in warmer/faster that could mean the I-80 counties also get 0.25”+ ice in exchange for a bit less sleet/snow. That’s definitely a distinct possibility as well.

I do think as noted by a few in here that QPF might be a thing in the LSV as noted on the newer NAM runs. If that’s the case, that’s probably a bigger limiting factor in higher ice totals than temps IMO. This isn’t Feb 3-4, the CAD is already locked in for most of the night with the precip attacking it. 

 

Thanks, great writeup/discussion. I have dropped below freezing here (31.8) so perhaps there will be a little more than what I bargained for. Speaking of which, do you know where I can find road temp data?

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12 minutes ago, CarlislePaWx said:

I forgot to give my conditions...

Currently 31.6 degrees and hasn't budged for more than an hour.  Dew point is 22 degrees and the wet bulb has decreased slightly from earlier to 28.4.  That at least helps increase the chances that temps will cool off a bit more once good precip is underway.

Latest radar shows serious juice about to enter southwest PA.  Definitely will be interesting to see how much sleet we all might get and how quickly it changes to zr.

I like seeing the heavy returns in the radar to our southwest. Hopefully we get a good dose of sleet before the freezing rain takes over.

 

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14 minutes ago, MAG5035 said:

I wouldn’t write off issues completely. Yea surface temps got a tad freezing today, they were supposed to. They should fall below freezing when precip arrives. Here’s what the 23z HRRR  just initialized 925mb (3000 ft) temps at. 

image.thumb.png.102e1c7bcbbc4a62ed1bd2af22f97f9f.png

They’re about 1 degree or so warmer at precip arrival around 4-5z. But yea -6 to -5ºC is about 21-23ºF. Pretty decent depth and strength of the low level cold, so that depth suggests to me sleet’s definitely in the equation the first couple hours all the way to the mason-dixon despite what p-type maps show. 

Here’s THV’s sounding generated from the HRRR at 05z (approximate precip arrival). The warm nose is elevated but easily notable, but the column is below freezing from 900mb (approx 4k feet) on down to the surface. 

image.thumb.png.5c8619f93132ea6ac6094e5f4b20e055.png

Otherwise I think CTP’s forecast/headlines are fine, though I probably would’ve considered a few more central/south like Centre, Huntingdon, Fulton, Franklin, for maybe a bit more freezing rain and less sleet. If 925-850 air advects in warmer/faster that could mean the I-80 counties also get 0.25”+ ice in exchange for a bit less sleet/snow. That’s definitely a distinct possibility as well.

I do think as noted by a few in here that QPF might be a thing in the LSV as noted on the newer NAM runs. If that’s the case, that’s probably a bigger limiting factor in higher ice totals than temps IMO. This isn’t Feb 3-4, the CAD is already locked in for most of the night with the precip attacking it. 

 

Thanks for the detailed analysis!

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13 minutes ago, Itstrainingtime said:

Radar does look very good to our west - it's going to come down to temperatures and how far we can fall below freezing at onset. 

With the precip set to arrive like a heavy wall, do you think this could help to cool the column a bit to provide more sleet for the first half of the storm?

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I see that the same collapse that has happened to you all to my south has happened up here in Williamsport.  The very stubborn Wunderground -- which stuck with 5-8 until past noon and then went down to 1-3 like the NWS advisory by late afternoon -- now is calling for a whopping inch.  The NWS is still sticking to 1-3 snow and sleet, .1-.2" ice in its advisory.

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2 hours ago, Ruin said:

Thinking this may bust

when you see a primary driving into NW Pa, I dont care what the models show, we torch .....  Yes, HP is in a nice spot, but without transfer sooner or notably south of MD line, its just not gonna work for most of us.  I saw very little CAD showing on the models, and yes temps are marginally ok for onset, but no pronounced wedge showed, and its just really hard to get long duration frozen w/ SLP track like that, unless antecedent cold is stout.  We just dont have that here.  Yes, we are gonna ice for a few hours, but surface is marginal at best, so without sleet, I'd think zr will even be less than modeled until you get to MSV and points NW.  if one looks at the 0z NAM, you can see much less snow even for northern tier counties.  Not trying to piss in anyone's cheerios but it is what it is.  

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Precip arrived just before 10. As expected, full blown pingers so far… with a tad of ZR in there enough to have a glaze on most non-treated surfaces. Already getting on the roads despite the road crews being on the scene. 27.5ºF. 

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15 minutes ago, Itstrainingtime said:

Rain here - no sleet at all at least at the onset.

Edit: it's raining hard.

You’ll have to see what the p-types are when that heavier stuff on your doorstep coming at you from the southern tier gets there. 

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