✨Pittsburgh PA ❄ Winter 2018-2019

[north pgh]

2 minutes ago, KPITSnow said:

Point and click upped my totals as did the hourly forecast. 2-4 inches of snow now.

I’m going bullish here and say we get 3-6.

HRRR short term models looking good so far.

[Mailman]

The HRRR is pretty amped.

[ChalkHillSnowNut]

3 minutes ago, Mailman said:

The HRRR is pretty amped.

Not so much for Fayette County...

[Mailman]

3 minutes ago, ChalkHillSnowNut said:

Not so much for Fayette County...

I have low expectations for here tomorrow.  

[MikeB_01]

HRRR has .75 QPF before the change over to rain. Lots of moisture

[MikeB_01]

3k NAM with 4 in snow before the rain. 

[MikeB_01]

1 minute ago, MikeB_01 said:

3k NAM with 4 in snow before the rain. 

should be noted that this run of the 3k also comes with .38 of ice. Might be a little over the top

[MikeB_01]

15z SREFs. 

[Rd9108]

I tend to favor the least amount of snow in this scenario just because we dont hold onto cold all that well. Maybe the HRRR is onto something but if we somehow get more than 3 inches I'd be shocked. 

[Mailman]

[north pgh]

This would be our largest snowfall of the Winter so far if this materializes. 

[KPITSnow]

I’m pretty pumped for this one. Isn’t going to be long duration but I think we can squeeze out 5-6 hours of sn+ before changing over.

 

Too bad we can’t lock in cold or we’d be looking at a good 10-15 type storm.

[jwilson]

I think a lot of the clown maps are deceiving due to their failure to differentiate snow and sleet.  Heavy wet snow would probably fall as a 7:1 to 12:1 ratio, while sleet is in the 2:1 or 3:1 range.  As an example, averaging out 10:1 snow ratio and 2:1 sleet ratio, the NAM gives Allegheny county between 1 and 1.25 inches of total precip.  Ferrier correction calls for 2.5" of snow, or so, which would be about 25% of the total precip.  Under that calculation, I'd estimate there's about an inch of just sleet, then some plain rain plus ZR towards the end.

That half inch of precip that falls as sleet shows up as another ~3-6" of snow on some models.  Looks like the 850s warm somewhere between three and six hours after onsent of precip.  Given our history and the way things have gone this winter, I'm inclined to sway towards a conservative snowfall estimate and thus a warmer overall solution.  The high being off to the East instead of our North gives me even more pause.

Using another example: the HRRR simulated radar still shows snow at 15Z, but the surface temps have already warmed above freezing.  That's four or five hours of snow, maybe even less.  This system could manage heavy rates (say >1" per hour), for sure, but I believe a system with that sort of convection is also more likely to flood in warm air at a quicker rate (someone correct me if I'm wrong on the science).

This is a long-winded way of me saying I'm still not buying into a significant snowfall along the warm "plain."  Places in the mountains and further north will probably see upwards of 10"; a shame we can't get in on that game.  It will be interesting, though, seeing how this storm verifies relative to the GFS vs. the Euro.

[RitualOfTheTrout]

17 minutes ago, jwilson said:

I think a lot of the clown maps are deceiving due to their failure to differentiate snow and sleet.  Heavy wet snow would probably fall as a 7:1 to 12:1 ratio, while sleet is in the 2:1 or 3:1 range.  As an example, averaging out 10:1 snow ratio and 2:1 sleet ratio, the NAM gives Allegheny county between 1 and 1.25 inches of total precip.  Ferrier correction calls for 2.5" of snow, or so, which would be about 25% of the total precip.  Under that calculation, I'd estimate there's about an inch of just sleet, then some plain rain plus ZR towards the end.

That half inch of precip that falls as sleet shows up as another ~3-6" of snow on some models.  Looks like the 850s warm somewhere between three and six hours after onsent of precip.  Given our history and the way things have gone this winter, I'm inclined to sway towards a conservative snowfall estimate and thus a warmer overall solution.  The high being off to the East instead of our North gives me even more pause.

Using another example: the HRRR simulated radar still shows snow at 15Z, but the surface temps have already warmed above freezing.  That's four or five hours of snow, maybe even less.  This system could manage heavy rates (say >1" per hour), for sure, but I believe a system with that sort of convection is also more likely to flood in warm air at a quicker rate (someone correct me if I'm wrong on the science).

This is a long-winded way of me saying I'm still not buying into a significant snowfall along the warm "plain."  Places in the mountains and further north will probably see upwards of 10"; a shame we can't get in on that game.  It will be interesting, though, seeing how this storm verifies relative to the GFS vs. the Euro.

These setups have brought heartache to me since I was a child watching all 3 weather stations watching for snow. That said on occasion in the face of all odds they work out. I agree the high being so far east is not really that helpful to us. I still think a general 2-3 with a surprise 4 isn't out of the question if we can really thump early on.

[RitualOfTheTrout]

3 hours ago, north pgh said:

This would be our largest snowfall of the Winter so far if this materializes. 

That would be something if it happens that way lol.

[Rd9108]

One thing for sure we may not get the accumulations that we want but we may have a good chance for some pretty heavy rates. That's why I want another 94 before a 93 just because the rates in that storm were so incredible yet I was only 3. 

[Mailman]

From WPC:

As precipitation falls, it will first occur into a column cold
enough for snow throughout, and a burst of heavy WAA snow is
likely from WV and points northeast into PA. This WAA thump of
snow will be accompanied by a brief but intense period of
750-600mb frontogenesis which is collocated with the saturated DGZ
in an environment with negative theta-e lapse rates. This suggests
intense snowfall rates which may exceed 1"/hr at times during the
morning across the Mid-Atlantic. The duration of intense snow in
the region will be limited as the warm nose will lift northward
turning precipitation from snow to sleet/freezing rain and
eventually rain by the evening. The guidance may be too quick to
warm the column due to reinforcement of the wedge by falling
precipitation, but eventually precipitation will changeover,
leading to a prolonged period of freezing rain across the terrain
of WV/VA and into PA. The heaviest snowfall in the Mid-Atlantic is
likely from the Panhandle of WV across MD and into Southern PA,
where WPC probabilities are high for 4 inches. The heaviest
freezing rain is likely in the terrain mentioned above, where a
risk exists for 0.5" of accretion even after the snowfall.

 

Source: https://www.wpc.ncep.noaa.gov/discussions/hpcdiscussions.php?disc=qpfhsd

[north pgh]

HRRR short term gives most of Allegheny County 4-5 inches between 6:00 am 11:00 am. Then changes over. It would be nice to see 1 inch per hour rates tomorrow morning. I have a meeting scheduled at 8:15. 

[MikeB_01]

HRRR short term gives most of Allegheny County 4-5 inches between 6:00 am 11:00 am. Then changes over. It would be nice to see 1 inch per hour rates tomorrow morning. I have a meeting scheduled at 8:15. 

That would be a thump. 5 hours of 1 in per hour. Roads will be a disaster.


.

[CoraopolisWx]

Gfs and Nam aren’t budging. 

Interesting to see who verifies tomorrow. Short terms look ok, so we’ll see. 

[MikeB_01]

Gfs and Nam aren’t budging. 
Interesting to see who verifies tomorrow. Short terms look ok, so we’ll see. 

Call it a wishcast if you want, but the short terms will have a better idea of the thermals as they develop. The collision between the HP sitting over NE and the stream of moisture from the south will develop overnight. Bernie mentioned the wet bulbs tonight. A good place to look if you want to see when the change over will occur.


.

[RitualOfTheTrout]

First flakes started falling right as I pulled into work this morning. Things look to be falling in line thus far, looks like a solid 35-40dbz returns just south of Allegheny County. All comes down to how much we can maximize this front end WAA.

I'd still hedge on a blend of short term hi-res models and GFS. My gut says GFS probably over does the warm air just a tad initially but the short term models over estimate how long the cold air hangs on.

[Burghblizz]

Very heavy snow on parkway east. I got a head start because I had meetings but this figures to be a debacle soon

[KPITSnow]

13 minutes ago, Burghblizz said:

Very heavy snow on parkway east. I got a head start because I had meetings but this figures to be a debacle soon

This is one of those days I wish employers would close down or have some consideration for employees not making it in to the office.

[RitualOfTheTrout]

Just now, KPITSnow said:

This is one of those days I wish employers would close down or have some consideration for employees not making it in to the office.

Worst possible timing the way its about to play out too for the commute. I bet a lot of these schools with 2 hr delays just close even though by late morning change over should be taking place the damage will be done.

Another heavy band looking to move into Southern Allegheny soon.

[MikeB_01]

Really coming down in the south hills. If you are not on the roads, it sure is puuurdy

[Rd9108]

1 minute ago, MikeB_01 said:

Really coming down in the south hills. If you are not on the roads, it sure is puuurdy

Roads were terrible on my way home from work. Lucky I was going against traffic but I'm gonna have to cancel my dentist appointment this morning because there is no reason to be on the roads. 

[KPITSnow]

It is REALLY coming down right now.

[ChalkHillSnowNut]

Already mixing in chalk hill... roads are pretty terrible-down the mountain in uniontown is just ice-not much snow

[KPITSnow]

I think I’m AGC, especially northern part, we overperform a bit. The radar returns indicate inch plus per hour rates for the next couple hours, so I think 3-5 inches is a pretty good call.