Central PA Winter 25/26 Discussion and Obs

[pasnownut]

3k ditto.  Small improvment thermally.  Will it add up to much....dunno, but 700/850's are a touch better for both in NAM suite.  

Going out to get wood n chores done.  Hoping to come back to good news.  Reel this one in boys n girls

[MAG5035]

3k NAM does try to bring the snow line back down as the secondary starts to take over, which keeps places like JST and AOO pretty much mostly or all snow but it slots before it really drops back into the Sus Valley. At the same time this model is showing the best comma head over western and northern PA and is probably the snowiest run yet for the max snows, which is exceeding 20” on Kuchera in west central PA. 

Sleet is prolific in the far PA southern tier/LSV and well,  just about everywhere else south of there. This is the kind of setup I feel there’s going to be a zone of multiple inches of sleet somewhere given the depth of the arctic air mass. That widespread? We’ll see. But that’s 2-3” of sleet on top of the 5-7” of snow it puts out in the LSV. 

Snowfall

 

[Mount Joy Snowman]

What's going on with the Canadians?  Did they drink too much again?  On the eve of our biggest event in years and they are a no-show ha.

[Itstrainingtime]

79/72 here in Key West. Just arrived at my airbnb for 2 nights. Can't believe I'm actually here. Overseas Highway...wow. 

The arctic front arrives here tomorrow night with temps getting down to the mid 50s. That doesn't happen every winter.

[Mount Joy Snowman]

Well I'll be damned, the CMC got out of bed.  It's slightly more aggressive with the sleet line but throws out a map that is basically identical to 0z.

[AccuChris]

18z rapid refresh was a slight improvement and the 19z HRRR was a tick colder as well at H17/18. Definitely going to be a nowcast situation as it unfolds


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[canderson]

Roughly what time would MDT flip to sleet according to that NAM (which I think is pretty dialed in)?

Was realy wanting 12” snow but don’t think it’s happening. Oh well. 

[Superstorm]

ICON colder too


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[Blizzard of 93]

The short range 12z Canadians also finally ran & the RGEM & HRDPS look a lot like the Euro, HRRR & GFS.

Every freaking model vs. the NAMs…

[Blizzard of 93]

14 minutes ago, Superstorm said:

ICON colder too


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Good to see…

[mahantango#1]

Bernie Rayno said this morning that he thinks the sleet will have a tough time making inroads on these negative dewpoints. But he said he's been wrong and right before on similar situations. That's his personal opinion.

[Jns2183]

Lessons from Arkansas below. Later I'll do an update for round two and look at Kentucky/Missouri, Ohio

Trust the NBM for the most likely total.
* Use the HRRR to define exactly where the heavy bands will set up (the "where").
* Keep the Euro in the mix to ensure you aren't being "fooled" by a high-res model (like the NAM) that might be missing a major moisture plume.

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[WmsptWx]

I mean, if the NAM scores a win here, they really need to look at halting decommission and supplementing it to where it's more than a short range specialist.

[mahantango#1]

We're probably less than 12 hours from the onset of our first major snowstorm in years. I hope you all enjoy no matter the outcome 

[canderson]

1 minute ago, mahantango#1 said:

We're probably less than 12 hours from the onset of our first major snowstorm in years. I hope you all enjoy no matter the outcome 

Amen! And it’ll stick around a long while afterward too, which is pretty rare overall 

[pawatch]

7 minutes ago, mahantango#1 said:

We're probably less than 12 hours from the onset of our first major snowstorm in years. I hope you all enjoy no matter the outcome 

I just go out when the snow is over and deal with what I got. Tomorrow’s snow I will probably clear a couple times. 

[Superstorm]

GFS slightly better for border counties.


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[Jns2183]

That's the 3k nam, reg nam, observed

The NAM suite’s performance during the Arkansas snowfall event was a case study in systematic failure, characterized by a severe northwest displacement and a critical underestimation of moisture transport. Both the NAM 3km and Parent models shifted the entire storm track 95–110 miles too far northwest, which effectively "erased" the heavy 7.8-inch snow core from Central Arkansas by placing it in a modeled dry slot. While the models were predicting 0.0" for Little Rock and Conway, the actual atmosphere was tapping into a rich Gulf moisture plume that the NAM fundamentally failed to resolve, leading to a massive +7.8-inch error at the storm's most intense point.
The root of this "NAM Gap" was a flawed thermal profile that modeled the 850mb "warm nose" much too aggressively and far north of its verified position. By over-amplifying the ridge ahead of the storm, the NAM physics engine incorrectly predicted that dry air would "eat" the incoming precipitation shield, when in reality, the column stayed cold and saturated enough for high-impact snowfall. For those tracking the storm's progression into the Ohio Valley and Northeast, the takeaway is clear: the NAM’s known dry bias and tendency to over-pump warm air can lead to a 100% miss in the transition zone, making a weighted consensus of the HRRR, Euro, and NBM a far more robust strategy for defining the true snow line.

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