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Western Pa / Pittsburgh area Winter Discussion ❄️☃️


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Just now, Ahoff said:

Whatever we end up with, it has put nearly the entire state of TEXAS in winter advisories.  I wonder if something like that has ever happened before?

I would be surprised if it’s happened in the past 30 years. I think the cold snap of late 2017-early 2018 had a massive part of the CONUS under advisories/warnings for snow and cold, but most of that was wind chill warnings and not snow/ice.

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Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
National Weather Service Pittsburgh PA
155 PM EST Sat Feb 13 2021

OHZ039>041-048>050-057>059-PAZ007>009-013>016-020>022-029-
WVZ001>003-140300-
/O.NEW.KPBZ.WS.A.0004.210215T0600Z-210216T1800Z/
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH-
Muskingum-Guernsey-Belmont-Mercer-Venango-Forest-Lawrence-Butler-
Clarion-Jefferson PA-Beaver-Allegheny-Armstrong-Washington-
Hancock-Brooke-Ohio-
Including the cities of New Philadelphia, Dover, Carrollton,
Malvern, East Liverpool, Salem, Columbiana, Coshocton, Cadiz,
Steubenville, Zanesville, Cambridge, Martins Ferry,
St. Clairsville, Sharon, Hermitage, Grove City, Oil City,
Franklin, Tionesta, New Castle, Ellwood City, Butler, Clarion,
Punxsutawney, Brookville, Aliquippa, Beaver Falls, Ambridge,
Monaca, Pittsburgh Metro Area, Kittanning, Ford City, Washington,
Canonsburg, Weirton, Follansbee, Wellsburg, and Wheeling
155 PM EST Sat Feb 13 2021

...WINTER STORM WATCH IN EFFECT FROM LATE SUNDAY NIGHT THROUGH
TUESDAY AFTERNOON...

* WHAT...Heavy snow possible. Total snow accumulations of 6 to 9
  inches possible.

* WHERE...Portions of northwest, southwest and western
  Pennsylvania, east central Ohio and northern and the northern
  panhandle of West Virginia.

* WHEN...From late Sunday night through Tuesday afternoon.

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could impact the morning or evening commute.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the latest forecasts for updates on this situation.

&&

$$

 

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.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
A series of shortwaves withing SW flow will increase wintry precipitation
chances Monday into Tuesday as the longwave central U.S. trough axis
shifts slightly eastward. At the sfc, a low will develop and deepen 
as it moves from the Mississippi Delta towards the northeast U.S., 
with cold air filtering into the region Tuesday as it moves farther 
east of the Upper Ohio River Valley. 

Confidence remains high in accumulating snowfall for much of the 
region and the second wave late Monday into Tuesday being the more 
significant punch. The combination of colder air, strong 
frontogenetic forcing and jet support will help produce potentially 
heavy snow around and to the north/west of Pittsburgh, a Winter 
Storm Watch was issued. Additional headlines are likely for the rest 
of the region as confidence increases in the timing and the type of 
impacts expected.

That said, granular details for each wave remain inconsistent between
models and from run to run for both incoming waves. Among the varying
details through the event include positioning of a mid-level 
frontogenetic zone; strength of ascent and associated connections to
a briefly coupled jet; strength and shifting of a baroclinic zone 
southeast of Pittsburgh leading to more of a wintry mix or freezing 
rain; efficiency of freezing rain accumulation; and potential dry 
slotting within the SW flow reducing accumulation efficiency. 

Increasing sfc high pressure and shortwave ridging will develop in
the wake of the exiting shortwave/low Tuesday night, with single
digit temperature likely for most locations.
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18 minutes ago, meatwad said:

Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
National Weather Service Pittsburgh PA
155 PM EST Sat Feb 13 2021

OHZ039>041-048>050-057>059-PAZ007>009-013>016-020>022-029-
WVZ001>003-140300-
/O.NEW.KPBZ.WS.A.0004.210215T0600Z-210216T1800Z/
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH-
Muskingum-Guernsey-Belmont-Mercer-Venango-Forest-Lawrence-Butler-
Clarion-Jefferson PA-Beaver-Allegheny-Armstrong-Washington-
Hancock-Brooke-Ohio-
Including the cities of New Philadelphia, Dover, Carrollton,
Malvern, East Liverpool, Salem, Columbiana, Coshocton, Cadiz,
Steubenville, Zanesville, Cambridge, Martins Ferry,
St. Clairsville, Sharon, Hermitage, Grove City, Oil City,
Franklin, Tionesta, New Castle, Ellwood City, Butler, Clarion,
Punxsutawney, Brookville, Aliquippa, Beaver Falls, Ambridge,
Monaca, Pittsburgh Metro Area, Kittanning, Ford City, Washington,
Canonsburg, Weirton, Follansbee, Wellsburg, and Wheeling
155 PM EST Sat Feb 13 2021

...WINTER STORM WATCH IN EFFECT FROM LATE SUNDAY NIGHT THROUGH
TUESDAY AFTERNOON...

* WHAT...Heavy snow possible. Total snow accumulations of 6 to 9
  inches possible.

* WHERE...Portions of northwest, southwest and western
  Pennsylvania, east central Ohio and northern and the northern
  panhandle of West Virginia.

* WHEN...From late Sunday night through Tuesday afternoon.

* IMPACTS...Travel could be very difficult. The hazardous
  conditions could impact the morning or evening commute.


PRECAUTIONARY/PREPAREDNESS ACTIONS...

Monitor the latest forecasts for updates on this situation.

&&

$$

 

There it is.

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25 minutes ago, Mailman said:

May be an image of map, sky and text that says 'Winter Storm Watch Hazards Winter Forecast Snowfall Totals 1AM Monday until PM Tuesday ThIn HEAVY HEAVYNW Areascold experience8 8to 12 inches snowi 24 hours. Clarion Salem Castle Butler Punxsutawney Additional nformation Philadelphia Clarion 8-12" Salem Weirton Castie Pittsburgh L cd lighter snow Butler Cambridge Zanesville unxsutawney Latrobe Washington Wheeling Uniontown -12" 8-12" Zanesville New Martinsville Morgantown There potential forsignificant snow, accumulations that impact monitor the latest Uniontown 3-4" Morgantown Martinsvill Davis National Weather Service Pittsburg,PA Davis 0-1 1-2 Weather.gov/PBZ/winter 2-3 6-8 Weather.gov/Pittsburgh'

So the NWS is forecasting 7” of snow in Pittsburgh with a 1% chance of 8” or more? (8” at the airport with a 12% chance of 8” or more.) Something has to give.

Essentially they’re issuing a watch saying “Allegheny County will likely receive 6-9 inches of snowfall” but their probabilities say it is very unlikely that most locations in the county will receive 8 inches. At the end of the day, winter storm watch/warning criteria are 8 inches in 24 hours, correct? The question basically boils down to, do you issue a winter storm watch for an area when the chance of that area meeting warning criteria is somewhere from 1-10%?

Alternatively, the messaging essentially reads “we don’t believe Allegheny County will meet warning criteria, but quite a few models say it will, so we’re going to issue a watch to cover ourselves in case it does happen.” The stakes are low when issuing a watch because you can always downgrade to an advisory.

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7 minutes ago, CoraopolisWx said:

Foggy misty February afternoon on top of a solid snowpack. 
Classic. 
 

ZL here as well.

Speaking of snowpack, depending on how this week plays out, would a large snowpack mute/slow down the effects of the pattern flip that is seemingly becoming more likely at the end of the month?

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Agree with others I'd like to see that boundary a little further southeast.  This isn't the typical "warm tongue" progression, but we have a screaming flow out of the south and the gulf as evidenced on the 500H patterns.  There's also the issue of the atlantic ridging, perhaps enhanced by the typical "Nina" response to develop a southeast ridge.  That ridge can be useful for us in Pittsburgh because it can shove the boundary further inland while warming the coastal plain, but there's also too much of a good thing.

None of the models have been great with thermal gradients this winter, and this particular pattern is even more delicate.  I wouldn't be confident in anything.  We'll probably have to wait and see where the boundary sets up on Monday to really get a sense of how this goes.

The GFS trends in the east have been to raise the heights along the ridge and decrease confluence or suppressive cold.  That trend needs to go back the other way a little.

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32 minutes ago, Rd9108 said:

I can imagine our area is probably a nightmare to forecast for the NWS. 

Oh it has to be. We haven’t had a event like this so far this year but I’ve basically taught myself to push any mix line 50-100 miles north of where modeled.

There was a huge Valentine’s Day storm in 07 or 08 I think and I was in slippery rock, and I don’t think Pittsburgh was really modeled to mix but the mix line made it all the way up to 80. 

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3 minutes ago, MikeB_01 said:


Lol everyone take a deep breath. I’m worried about the mixing too but I’m not jumping ship after one run. Sometimes these models wobble. Like a windshield.


giphy.gif


.

True. The NAM ticked about 500 yards to the SE with its 18z run. Even so, we should probably go on the record and issue a Youngstown special warning.

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3 minutes ago, TimB84 said:

True. The NAM ticked about 500 yards to the SE with its 18z run. Even so, we should probably go on the record and issue a Youngstown special warning.

I called the Youngstown special thats my call but I will say let's settle down when it comes to 18z models. If 0z looks as bad or worse than yes the trend isn't our friend. 

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2 minutes ago, Rd9108 said:

I called the Youngstown special thats my call but I will say let's settle down when it comes to 18z models. If 0z looks as bad or worse than yes the trend isn't our friend. 

Ah yes, the old adage of the 18z models again. It may or may not be true, but at least it allows us to hold off on disappointment for 6 hours.

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3 minutes ago, Ahoff said:

One run. Let’s chill out.

Rationally speaking, you’re correct. This run also shifted the Thursday storm back into a still not great location for us but at least not running the low through Indianapolis so we get snow instead of ice before the warm air blasts in, so we actually end up with similar snow totals for the week before the thaw Thursday night.

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5 minutes ago, TimB84 said:

Rationally speaking, you’re correct. This run also shifted the Thursday storm back into a still not great location for us but at least not running the low through Indianapolis so we get snow instead of ice before the warm air blasts in, so we actually end up with similar snow totals for the week before the thaw Thursday night.

Exactly it goes back and forth.

i imagine we should be starting to shift to the Mesos at this point or very soon.

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