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Wintry January 21-23 2025

Just quoting what Eric Webb said yesterday for those who missed it…
Webberweather53 said:
My experience with these brutally cold Arctic air masses that get dumped onto the Rockies is that they usually end up dropping southward along the Rockies more quickly than the models lead you to believe in the medium range.

Pouring extremely cold air into a trough will cause it to dig more quickly and the positive potential vorticity & stability anomalies that are created above the intense low level cold dome “drag” on the trough base, causing it to also dig more. Feedbacks can then occur with a shallow, but intense low-level northerly barrier jet further shoving the cold air mass further south. The GFS & GEFS are notoriously bad at handling these processes and I expect them to eventuality fully give into the EPS & GEPS.
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Let's play Where's Waldo!

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Just FWIW I notice the difference between the GFS and Euro (and every other model) is how they handle the ridging out west. The GFS has shallower ridging and is further east. Our wave doesn’t dig as much and gets sheared out whereas the Euro camp has a taller ridge and lets the energy dig and doesn’t shear out. GFS does have a progressive bias and that may be in play. We will see.
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1300m said:
F-fff-fold.

It’s like the winter storms of yore. GFS always is the last to latch on.
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Jan 96 is a classic example. That was similar setup with a s/w riding down the backside of the PV. The PV and associated AF weren't nearly as far south but this is the storm that crowned the ECMWF as king

The Gary Gray Files - Jan '96

I had these archived and published on a site but no longer hosting it. Figured I would post them all here. These are the usenet posts from Gary Gray leading up to the Blizzard of '96. Keep history alive. Jan 3 1996: Subject: The Mid-Atlantic's Turn??... <1/3> From: [email protected] (A.K....
www.americanwx.com www.americanwx.com
 
We are crossing the less than 120 hour mark , where our energy is rolling out of the SW and beginning the fun and games.

Big runs at 0z tonight through 12z tommorow. Once it (our energy ) ejects,theres no turning back and the cold aint going nowhere.

Started seeing unanimous consent ( minus mainly GFS OP) already. This is a slam dunk unfolding in front of our eyes. It will get notorized by the notary by 12z tommorow. All that will be left to decide after that point is if you gonna forecast 6-12 or 12-18. And ptypes all the way down to north Florida.

Enjoy the ride. Been a long time coming. Fun part is gona be figuring out ratios for the good reasons and not worst case with this one .

My 2 cents for what its worth.
 
I'm late here, but I found this part of the discussion by KCAE interesting, especially given that GSP apparently doesn't mention ensembles...

While the cold outbreak is high confidence, what follows is
less confident, but quite interesting. All major pieces of
guidance, including the majority of GEFS and ECE members show
some sort of coastal low developing along the southeastward
extent of the primary cold dome. Climatologically, this type of
setup is favorable for wintry precip in the Carolinas and
eastern GA, but it raises a series of possible outcomes as well,
which are shown well in guidance now. The EC and Canadian
(along with their ensembles) show a classic southern slider
overrunning event; ECE probs of greater than 1.0" of snow over
much of the area continues to exceed 40% for multiple runs in a
row now. Ditto for the Canadian. However, these mean probs are a
bit biased towards the high end members of the ensembles. These
high end members raise their own interesting point by
themselves however. Now on the other end for the possible
Tuesday- Thursday system, the GEFS over the last few runs
presents the classic suppressed solution with the surface high
dragged too far south and forcing any synoptic forcing well
south. So, at this point, based on the extent of the airmass,
typical trends in ensembles in the 6-10 day window, and the
current depictions, confidence is increasing in some wintry
precip in the Carolinas and eastern GA; however, as with all
possible wintry precip systems around here it will take time to
figure this out.

They don't have anything in the forecast, but they're honking in this discussion, and I can say local mets are as well.
 
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