Pittsburgh, Pa Winter 2023-24 Thread.

[blackngoldrules]

Not sure if I've ever seen the models this far apart this close to a potential storm. I guess still a lot of uncertainty how this is going to set up and such a high margin of error. Whoever gets the big snows from this is going to be lucky. I'm starting a new job on Tuesday. Would be my luck if THIS one would happen to nail us! Lol

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[blackngoldrules]

This guy put out a "first call" map for what it's worth. Still so much uncertainty with this. I think maps like this are going to change a lot between now and the event.

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[Burghblizz]

7 minutes ago, blackngoldrules said:

Not sure if I've ever seen the models this far apart this close to a potential storm. I guess still a lot of uncertainty how this is going to set up and such a high margin of error. Whoever gets the big snows from this is going to be lucky. I'm starting a new job on Tuesday. Would be my luck if THIS one would happen to nail us! Lol

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I’ll take it since you guys got the lake band .  But yeah, it looks like up in the air not only regionally, but locally. Wouldn’t be shocked if it was another one that split our area in terms of impact. Model biases seem out the window too. 

[RitualOfTheTrout]

1 hour ago, blackngoldrules said:

Not sure if I've ever seen the models this far apart this close to a potential storm. I guess still a lot of uncertainty how this is going to set up and such a high margin of error. Whoever gets the big snows from this is going to be lucky. I'm starting a new job on Tuesday. Would be my luck if THIS one would happen to nail us! Lol

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NWS with a good discussion in the uncertainty:

.LONG TERM /MONDAY THROUGH FRIDAY/...
KEY MESSAGES:

- The next potential system will impact the region late Monday
  into Tuesday, with a range of potential winter weather-
  related impacts.

---------------------------------------------------------------

The cut-off low will develop a coupled surface low over the
Mississippi Valley early Monday. As the cut-off draws eastward,
it will attempt to re-phase into zonal flow over our area
Monday night through Tuesday. In all likelihood, the system will
start as rain late Monday. From there, the details get dicey.
The strength of the cut-off low will determine various aspects
of the surface low behavior. This could play out as a couple
scenarios over the forecast area.

1) The upper-low is weaker and phases more rapidly into zonal
flow. This would act to keep the surface low track more
progressive and farther to the south. Coastal low development
would then dominate into Tuesday morning. Because the low track
would be farther away, local northerly flow would be weaker.
This would lessen the magnitude of cold and dry advection
around the backside of the system. An area of frontogenesis is
possible, centered over northern West Virginia on the northwest
side of the low, though temperatures would likely be too warm to
result in snowfall. This solution would result in mostly rain
across the area with a lower probability of appreciable snow
accumulation. This is reflective of the NBM 10th percentile,
where totals amount to zero across the lowlands with a light
accumulation for the ridges.

2) The upper low is stronger and slower to re-phase into zonal
flow. Though subtle, this would affect surface low behavior and
the eventual coastal low development. Under this scenario,
ensembles indicate the surface low has a tendency to pull back
and collocate under the upper low before the coastal low takes
over. This is important. A stronger low across the West Virginia
interior could influence three processes. First, stronger north
to northeast flow on the northern side of the system would
advect cooler and drier Canadian air, capable of wet-bulbing
temperatures further. Second, the area of frontogenesis would
more likely be in an area that is cold enough to support
snowfall. Third, latency time of favorable lift increases as the
cut-off is slower to incorporate into the upper flow. These
factors could lean towards snowfall amounts toward the higher
end of the distribution. Even then, there is still uncertainty
with the exact track that the cut-off low may take, adding
uncertainty to the area that may see the highest snowfall
totals. This scenario is more reflective in the NBM 90th
percentile, which shows a sizable tract of 6"+ of snow across
western Pennsylvania and the northern West Virginia panhandle.

With the spread as large as it is between these two scenarios
and still a great deal of uncertainty in track, the current
forecast is reflective of some "middle-ground". Though not
necessarily the "most-likely" scenario, will opt to continue to
trend toward the more likely solution as more information
becomes available in subsequent updates.

[Burghblizz]

Real nice discussion. We normally call it out when they mail it in too, but that’s a good one 

[Rd9108]

NAM is weird but has a mini jack pot for us. Expect the least hope for the best is all I'll say. Would like to see the euro stay consistent and gfs to come south.

[Rd9108]

Last post for a bit. How is the gfs so much different compared to the RGEM. Hopefully it's wrong. 

Like how does the Canadian show this

 

And the gfs has 12+ just a county and a half north. 

[CoraopolisWx]

11 minutes ago, Rd9108 said:

Last post for a bit. How is the gfs so much different compared to the RGEM. Hopefully it's wrong. 

It does seem a bit odd how the gfs moves the low due north that far before transferring. 

[TimB]

And just like that, it’s gone on the GFS. 

[Burghblizz]

7 minutes ago, CoraopolisWx said:

It does seem a bit odd how the gfs moves the low due north that far before transferring. 

If that were the only model I saw, I would think we were in for a plain rainstorm, and somewhere between Columbus and Detroit eventually gets nailed. GFS usually doesn’t tick SE in this range. 
 

NWS doesn’t seem to be buying it. The non-event scenario would be more due to a progressive, weaker storm that doesn’t tap any cold air (as opposed to a larger one that charges north). Probably won’t have a great idea for 24 hours. 

[north pgh]

We may not find out until Sunday night or Nowcasting on Monday.

[Burghblizz]

1 minute ago, TimB said:

And just like that, it’s gone on the GFS. 

That was the Canadian being contrasted to the GFS. GFS is just too amped up.

[RitualOfTheTrout]

33 minutes ago, CoraopolisWx said:

It does seem a bit odd how the gfs moves the low due north that far before transferring. 

Its been consistent with doing that in some form. Looping back through the previous runs that SWPA warm tongue / dryslot signal is on display.

Crazy the difference in solutions right now on the models. 

[north pgh]

7 minutes ago, RitualOfTheTrout said:

Its been consistent with doing that in some form. Looping back through the previous runs that SWPA warm tongue / dryslot signal is on display.

Crazy the difference in solutions right now on the models. 

Agree 100%.

Odds are in our favor for a decent hit only because we haven't had one for so long but are against us because we are most likely to get fringed.

[TimB]

GEFS mean looks awesome.

[Burghblizz]

26 minutes ago, TimB said:

GEFS mean looks awesome.

Was just looking at that. Could be another sign that the it’s GFS Op versus the world. 

[TimB]

14 minutes ago, Burghblizz said:

Was just looking at that. Could be another sign that the it’s GFS Op versus the world. 

The depth maps are meh, so I’m thinking it’s bad temp profiles and tough to get accumulation anywhere close to 10:1 even with a mean of 7”, but who knows.

[TimB]

Razor thin margins, but love when this gets put in the point and click.

 

That said, the Euro took a slight shift north at 12z. Far northern Allegheny county is still fine, but the rest of us are riding the slop line.

[Burghblizz]

Euro looking like the GFS did yesterday. 8” IMBY….but AGC is the battleground with a rapid drop off. 

[RitualOfTheTrout]

4 minutes ago, Burghblizz said:

Euro looking like the GFS did yesterday. 8” IMBY….but AGC is the battleground with a rapid drop off. 

Its such a narrow margin for victory, minor changes in the handling of that upper low will be all the difference.

Im low elevation, and generally my yard does poorly in marginal setups when a few miles any direction is usually significantly better, so I have little optimism.

Going to take some good rates to dynamically cool the column and overcome warm surface, but wherever gets that there should be impact, outside of that probably just wet roads etc. Unless the Canadian is right then everyone loses. 

 

 

[jwilson]

The CMC is the only one of the majors that keeps it an open wave, meaning the lows - at all levels - never close off.  So the s/w doesn't deepen and it bounces along the confluence out to sea.  It's subtle, but it is also a tad bit stronger and further south / faster with the confluence.  There's a suppressive element to that difference.

There's not a ton of NS energy getting phased into the center in any case.  The good and bad of that is we have a cap on how far north it can realistically go, but it also means we cap how deep the storm can intensify.  Most of that energy acts more of a kicker to knock the system East, which also means the center of LP stays farther away and limits its influence on us.

Obviously, we're coming into this event with extremely marginal cold air.  It's going to be 50 degrees Monday.  In a system like this, that doesn't matter quite as much, but the antecedent thermals are always relevant to some extent.  Both the Euro and GFS are now keeping the better totals north of PIT metro.

Based on experience, I think I see enough red flags to bail on this one, at least here in the South Hills.  I'll be happy if I'm wrong, but I would honestly be quite shocked to see this one come back south and bullseye the Pittsburgh localities.  That would go against conventional wisdom.

Not saying it's impossible, but I'm playing the odds here - if you're into betting, it's like taking the favored home team.

[Burghblizz]

9 minutes ago, jwilson said:

The CMC is the only one of the majors that keeps it an open wave, meaning the lows - at all levels - never close off.  So the s/w doesn't deepen and it bounces along the confluence out to sea.  It's subtle, but it is also a tad bit stronger and further south / faster with the confluence.  There's a suppressive element to that difference.

There's not a ton of NS energy getting phased into the center in any case.  The good and bad of that is we have a cap on how far north it can realistically go, but it also means we cap how deep the storm can intensify.  Most of that energy acts more of a kicker to knock the system East, which also means the center of LP stays farther away and limits its influence on us.

Obviously, we're coming into this event with extremely marginal cold air.  It's going to be 50 degrees Monday.  In a system like this, that doesn't matter quite as much, but the antecedent thermals are always relevant to some extent.  Both the Euro and GFS are now keeping the better totals north of PIT metro.

Based on experience, I think I see enough red flags to bail on this one, at least here in the South Hills.  I'll be happy if I'm wrong, but I would honestly be quite shocked to see this one come back south and bullseye the Pittsburgh localities.  That would go against conventional wisdom.

Not saying it's impossible, but I'm playing the odds here - if you're into betting, it's like taking the favored home team.

Good write up. The only thing that feels different to me is how far south the NAM and Ukie are (with Canadian being a non storm). Gives me at least some hope that the final solution ticks back south instead of the other way. 

[TimB]

18z NAM has us in a good spot but it continues to tick north. I’m worried we’re in a precarious spot and this is just part of a bad trend.

[Rd9108]

Lock it in. Would like to see the gfs either stop moving north or tick south or else Bernie Rayno is going to be right about the snow going just to the north of PGH. 

[Rd9108]

Gfs not budging. The low was slightly south of 12z before transfer but the area is just flooded with warm air. My guess is the gfs is most likely gonna be right unfortunately. It just seems like in recent years anytime there is any sign of warm air/warm tongue that it's always north of even the models. Any hope is the cold air pushes further south than progged/more confluence. I'm not saying this one is over, it's just that we most likely willnnot win in this scenario unless we see some better trends...

[TheClimateChanger]

Looks like a classic late spring snowstorm. Sort of reminiscent of that March 20-21, 2018 event, which brought up to 10.5” at the airport if I recall correctly. I think we were looking at 2-4” heading into that event. Only question is how far north this event tracks. Looks like somebody will have a nice accumulation. As is the case with spring snows, shouldn’t last too long as temperatures should be above freezing most days.

[TimB]

27 minutes ago, Rd9108 said:

Gfs not budging. The low was slightly south of 12z before transfer but the area is just flooded with warm air. My guess is the gfs is most likely gonna be right unfortunately. It just seems like in recent years anytime there is any sign of warm air/warm tongue that it's always north of even the models. Any hope is the cold air pushes further south than progged/more confluence. I'm not saying this one is over, it's just that we most likely willnnot win in this scenario unless we see some better trends...

It’s over. 6z GFS had the 6-8” line clipping a portion of the county, at 18z no one in Allegheny gets more than 3-4.

[Rd9108]

Just now, TimB said:

It’s over. 6z GFS had the 6-8” line clipping a portion of the county, at 18z no one in Allegheny gets more than 3-4.

Atleast it's over now and not 24 hours out. Like I said too I have a feeling this forces the rain/snow line even further north than the gfs is modeled. Gotta see some changes at 0z tonight if there's any hope.

[TimB]

What a dumb winter. Can’t believe we got two of these in a row, and this one is somehow worse than last year, which was the worst winter that’s ever occurred here.

[Rd9108]

18z euro north again fwiw. Need to see some type of bleeding to the north stopped tonight or tomorrow or else this thing is going to Youngstown/Cleveland. NAM is next up.