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Central PA - Winter 2021/2022


Bubbler86
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51 minutes ago, Blizzard of 93 said:

The 3k NAM came in colder and really delivers the heavy sleet even to the LSV.

 

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The pendulum once again has reversed and is heading back away from majority ZR to majority sleet.  Still have another 36 hours to push the snow line further towards our region.  While heavy sleet is horrific for the roads, it can't hurt the trees and shrubs.  Between the two I'd much prefer IP over ZR.

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Great discussion from CTP this morning.

”The storm of note will be gathering over the TN valley on Thursday. Some light precip (snow??) is expected to arrive later in the day. NAM very aggressive with generating meas precip/light snow over much of the CWA during the daylight hrs. However, other model solutions hold it off for almost all day long. Much uncertainty remains with how this storm will affect the CWA. At this point, the low center will prob pass over our NW counties early Fri AM. Warm air flows in overhead Thursday night, and will likely make a prolonged period of mixed precip. Cold air will get reinforced by a cold air damming setup Thursday night. Broad srly 8H winds >40KT will supply plenty of GOMEX mstr. Most places north of the Turnpike get down below freezing Thurs evening and stay there until mid-morning Fri. The setup/signal for FZRA is strong(est) over the Laurel Highlands. WPC guidance, BUFKIT soundings and SREF probs make a good case for 0.25"+ of FZRA between 00Z and 12Z at JST. QPF thru that time is >1" with some of that falling as PL and it could turn to rain near the end of the night in Somerset Co. The sleet-heavy soundings from NAM put down 1" of sleet accums (at like a 4:1 SLR). That amount of sleet can wreak havoc on the roads, esp if people drive on it and compact it. However, the sleet would cut down on snow totals. The nrn tier is least susceptible to a turn-ovber to sleet. However, no guidance points to all snow in the north - it turns to a mix there, too. Precip type change-over timing is very much in doubt. So many what- ifs give low confidence to snow/sleet amounts, and the ice accums, too. Have decided to post a winter storm watch for the Laurels as this appears to be the most-certain area to garner signif ice accretions. Everyone south of I-80 may get 0.10-0.25" of ice, too, and may eventually go to an advy, but confidence in warning levels of snow/sleet/FZRA not there, yet. Thus, no watches elsewhere at this point. I could see posting watches/warnings later for sub- criteria amounts of straight snow if we end up getting a sig amount (1"+) of pure sleet, or sleet topped by a sig glaze of ice. It`ll just harden into a brick, and is not easy to clear from the roads/sidewalks. We had that once already this winter locally. Friday looks like it will be a "snow day" for most schools in Central PA.”

 

 

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The local ABC-27 Met. Brett this morning said he wasn’t expecting much trouble on the untreated roads.

CTP disagreed with that in their discussion that I just posted.

If places get a few hours of sleet before the freezing rain, this will provide a colder surface for freezing rain accretion.

Most models get temps from the high 20’s to low 30’s even in the LSV, so sleet + freezing rain could create a “brick” on surfaces as CTP mentioned.

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1 minute ago, Blizzard of 93 said:

The local ABC-27 Met. Brett this morning said he wasn’t expecting much trouble on the untreated roads.

CTP disagreed with that in their discussion that I just posted.

If places get a few hours of sleet before the freezing rain, this will provide a colder surface for freezing rain accretion.

Most models get temps from the high 20’s to low 30’s even in the LSV, so sleet + freezing rain could create a “brick” on surfaces as CTP mentioned.

I agree sleet will cool the road surfaces faster.

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26 minutes ago, Blizzard of 93 said:

The local ABC-27 Met. Brett this morning said he wasn’t expecting much trouble on the untreated roads.

CTP disagreed with that in their discussion that I just posted.

If places get a few hours of sleet before the freezing rain, this will provide a colder surface for freezing rain accretion.

Most models get temps from the high 20’s to low 30’s even in the LSV, so sleet + freezing rain could create a “brick” on surfaces as CTP mentioned.

Though i'm not a fan of his, he knows the area. I agree with him this time. 

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Overnight temp of 60 and total rain of .13".  My thoughts on the upcoming event:

I don't see this as an overly impactful event for those of us in the LSV.  The Low to our west is a little too high and tight and the High above us trickles east just a smidge too much, all without a truly arctic airmass in place  There is a deep warm layer centered around 800mb, on the back of strong S to SW flow, that is only going to get deeper and warmer as the event progresses.  Despite tomorrow turning nice and cool, marginal surface temps just below freezing and recent warming could make accumulation of whatever falls tricky.  The short-term models are also starting to pick up on the presence of a pretty significant dry slot over much of central PA late Thursday night, which ironically enough, could help with the ice accretion as drizzle would be more likely to accrete than a more moderate rain in a marginal temp environment.  All in all, I see at best a trace of wet snow at the onset followed by a brief period of sleet and then an extended period of freezing rain/drizzle.  Whether the roads get dicey at all may depend on whether we can get a layer of sleet to coat them first, as others have mentioned.  I think things soften up by midday and outside of the early morning time period, don't see too may issues.  The obvious caveat is that CAD can often overperform so we'll have to keep an eye out for that but I'm just not really seeing it with this setup.  I think the more serious impacts will be confined to the more northern areas of the forum.  I am absolutely not buying some of the more extreme freezing rain outcomes being depicted on some of the models (shocking I know) and think anything approaching a quarter inch would be big for our area.  I should also add that the only meaningful snow I see falling is in extreme northeastern PA.  In short, warm air wins again.  As always, I would love to be wrong.

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3 hours ago, Blizzard of 93 said:

Great discussion from CTP this morning.

To me this is like the last time when it comes to headlines. Consideration of watch/warnings for sub criteria is specifically stated in that AFD considering the combo impact of accumulating snow/sleet and freezing rain. As it should be, so why not just issue the watch? There definitely is model support for the “potential” of warning level ice over a decent portion of C-PA. Personally for starters I think watches should match up with the ones BGM issued across the state I-80 north and tie in to the Laurels counties plus a few more central counties. Could argue just issuing the whole CWA under one if they’re going the impact over criteria route. The Sus Valley is going to get decent sleet/freezing rain up front too. The northern tier probably has the toughest case for a watch. Some of those counties require 0.5” of ZR for a warning, which probably isn’t happening up there and it’s likely going to mix too much to get near warning criteria snow in most spots. Just a lot of different scenarios to consider and pretty much all of them in this setup are pretty high impact regardless of thresholds so I just have the opinion of issue the watch and transition to advisory as needed. I think it alerts the general public better that way. 

I see this storm playing out one of two ways. One is you have more frozen (likely mostly sleet), which 1-2” or so (or even just an inch) of that is a high impact event in itself when it comes to roadways. That changes to freezing rain and a glaze of ice, which could still approach warning criteria in some areas anyways. That’s a pretty high impact event. Or two, deeper warmth aloft floods in (a theme this winter) and you have some sleet and a boat load of freezing rain over a pretty widespread part of C-PA. Also a high impact event. And this potential is much more viable than the Feb 3/4 event was. We’re not racing against time with bleeding cold into an ongoing rainstorm. That will be in place tonight. Placement and strength of the high pressure is very good for CAD and as I mentioned last night it doesn’t get moved out of the way.  This has a pretty traditional drawn out ice storm look. And no I don’t like either of those scenarios. Southern stream waves are at a premium this winter, and here we are wasting a bunch of QPF again.

With the snow aspect, I’ll be honest.. I think CTP’s current map is too optimistic. Models have generally locked into tracking the primary low into PA. So 4-6” probably stays above US 6 (maybe even out of PA completely) and the rest of the accum area is 1-3”. I think sleet is going to have a bigger role than snow when if comes to frozen. Just too much warmth aloft. Getting some snow out of this event heavily depends on if we generate WAA precip earlier tomorrow. The NAM had been the most aggressive with that, but the 12z looks like the other models, waiting until about 0z tomorrow and keeping initial precip mostly south of the M/D.

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Temps have started to steadily fall off since about 7am this morning, going from 57ºF to currently 42ºF. It cracked 60ºF for a while just after midnight last night, just your usual 35 degree above average Feb night.

0.44” was the measured rain total from yesterday.

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1 minute ago, MAG5035 said:

Temps have started to steadily fall off since about 7am this morning, going from 57ºF to currently 42ºF. It cracked 60ºF for a while just after midnight last night, just your usual 35 degree above average Feb night.

0.44” was the measured rain total from yesterday.

Is there a cold front coming through?

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1 hour ago, Mount Joy Snowman said:

Overnight temp of 60 and total rain of .13".  My thoughts on the upcoming event:

I don't see this as an overly impactful event for those of us in the LSV.  The Low to our west is a little too high and tight and the High above us trickles east just a smidge too much, all without a truly arctic airmass in place  There is a deep warm layer centered around 800mb, on the back of strong S to SW flow, that is only going to get deeper and warmer as the event progresses.  Despite tomorrow turning nice and cool, marginal surface temps just below freezing and recent warming could make accumulation of whatever falls tricky.  The short-term models are also starting to pick up on the presence of a pretty significant dry slot over much of central PA late Thursday night, which ironically enough, could help with the ice accretion as drizzle would be more likely to accrete than a more moderate rain in a marginal temp environment.  All in all, I see at best a trace of wet snow at the onset followed by a brief period of sleet and then an extended period of freezing rain/drizzle.  Whether the roads get dicey at all may depend on whether we can get a layer of sleet to coat them first, as others have mentioned.  I think things soften up by midday and outside of the early morning time period, don't see too may issues.  The obvious caveat is that CAD can often overperform so we'll have to keep an eye out for that but I'm just not really seeing it with this setup.  I think the more serious impacts will be confined to the more northern areas of the forum.  I am absolutely not buying some of the more extreme freezing rain outcomes being depicted on some of the models (shocking I know) and think anything approaching a quarter inch would be big for our area.  I should also add that the only meaningful snow I see falling is in extreme northeastern PA.  In short, warm air wins again.  As always, I would love to be wrong.

Great, great writeup my friend. Elliott at MU agrees with you, and so do I. I've said very little about this "event" as I feel that ice projections are usually vastly overdone, especially for us southern tier folks. My thoughts are based off of past history and the conditions leading into this particular storm. 

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