2013-01-29 FORECAST: TX/OK/AR/LA

[TrumanBoyer]

Actually the SPC has postings for both...

D4 Tue, Jan 29, 2013 - Wed, Jan 30, 2013
D5 Wed, Jan 30, 2013 - Thu, Jan 31, 2013

At this time D5 is expected to be a QLCS event
but Alabama tends to be really soupy this time of year,
and it would not surprise me at all to see supercells out ahead of the front.

D4 looks best for tornadoes,
and it is really unusual to see tornadoes mentioned in a Day 4 forecast,
especially in JANUARY.

My question is, of course, where will we see the action ?
The prog covers an awful lot of real estate,
and I think its too soon to be betting on a bulls-eye,
but my Gut says Arkansas -- after dark.

Anybody else watching this ? Any Thoughts ?

MODS -- I got a little excited, and posted this early.
I Hope I did not break any rules.

Truman

 

[Jeff Duda]

Boy, that's some hella moisture advection from the GFS. 60 degree dewpoints all the way up to I-70 and even a little north? Wow, at least when compared to what the NAM and SREF are indicating. As is pretty typical with a cold-season setup in the south, shear is really no problem, and instability is at a premium. I know SPC last updated the Day 4-8 outlook overnight so the forecaster didn't see this morning's runs, but areas of C/S TX stood out to me when taking a brief look just now. Instability is much better there, and low-level flow is a little more backed. While overall shear is also slightly lower, storm speeds and shear vectors are more favorable for discrete supercellular activity there than points northeast. However, since there is progged to be at least 100 J/kg of CAPE in the entire threat area, I wouldn't be surprised to see several tornado reports. You just don't need much CAPE in the winter to get tornadoes in the south, at least when moisture is not in question (as it isn't with this system).

There is still some variability in the forecasts, though, so details may change over the next 60-72 hours.

 

[Brett Roberts]

I know it borders on blasphemy to bust out dates like this several days in advance, but there are striking similarities between "Super Tuesday" (2008-02-05) and the 12z GFS prog for Tuesday. The H5 pattern across North America, the elongated but decently-deep surface low, and respectable moisture return by mid-winter standards all conjure up memories of that event. I would not be surprised to see a significant tornado event across the Ozarks and parts of the mid-South *if* this run proves accurate in its synoptic evolution.

However, even the generalities of this forecast are not clear-cut, given the wild model swings of late. For what little it's worth at this range, the NAM paints a much different picture, with a strongly positive-tilt trough that fails to induce a significant low-level cyclone. The ECMWF and GFS had alternately shown scenarios ranging from a flatter, low-amplitude trough to a SW cutoff low over the past several days, but have admittedly come into good agreement since yesterday morning. If the global models hold course through tomorrow and the NAM hedges in their direction, it will be time for AR and surrounding areas to start paying close attention.

 

[Shane Adams]

I'm not sure I buy into the NAM much at this point. It's going crazy on moisture return, but isn't reflecting this in the instability parameters at all. I'm not understanding why there isn't a CAPE spike on the NAM in conjunction with the elevated moisture and 70s temps. Seems a little off to me. But as usual, it's keeping things further west, which tends to be accurate many times. Wouldn't surprise me to see the GFS start to gradually pull back a bit as well, to create a "happy medium" with what the NAM advertises. Still, the surface parameters on the NAM just don't add up for me attm, so I'll await further runs to see if it can get a better handle on things. If anything even remotely comes to pass as advertised, I'd expect the real-world placement for the best shot at chaseable diurnal activity to be in the area from DFW-Waco, and points east. Roads and terrain go to crap too far east from there, and as already mentioned in a previous post, darkness will be an issue as the system moves east throughout the latter half of the day. My money (if anything happens) would be around the Corsicana area to start, awaiting development west or southwest. With the expected storm speeds, I'd want to be at least an hour downstream from where I expect initial development.

We'll see how it looks tomorrow, been a roller coaster thus far.

 

[Jeff Duda]

I'm not sure I buy into the NAM much at this point. It's going crazy on moisture return, but isn't reflecting this in the instability parameters at all. I'm not understanding why there isn't a CAPE spike on the NAM in conjunction with the elevated moisture and 70s temps. Seems a little off to me. But as usual, it's keeping things further west, which tends to be accurate many times. Wouldn't surprise me to see the GFS start to gradually pull back a bit as well, to create a "happy medium" with what the NAM advertises. Still, the surface parameters on the NAM just don't add up for me attm, so I'll await further runs to see if it can get a better handle on things. If anything even remotely comes to pass as advertised, I'd expect the real-world placement for the best shot at chaseable diurnal activity to be in the area from DFW-Waco, and points east. Roads and terrain go to crap too far east from there, and as already mentioned in a previous post, darkness will be an issue as the system moves east throughout the latter half of the day. My money (if anything happens) would be around the Corsicana area to start, awaiting development west or southwest. With the expected storm speeds, I'd want to be at least an hour downstream from where I expect initial development.

We'll see how it looks tomorrow, been a roller coaster thus far.

CAPE is not high in the NAM because lapse rates above the PBL are crap. It's just too warm in the mid-levels due to the area being so far from the mid-level cold core of the system.

 

[TrumanBoyer]

Here in MD mid-50 temps and moderate south winds have been forecast for mid-week for over a week now. Crazy moisture fetch would not surprise me at all, but I have not looked at Gulf SSTs yet. Wednesday (day 4) now has severe blob over my stomping grounds with I-81 as a sort of axis. PERFECT !!

Is it blasphemy to pray for bad weather ?
-T

 

[Mike Johnston]

SPC upgraded the Day 2 area to a moderate risk this morning, which was somewhat expected. Besides that, I like the fact the models are beginning to show:

1. That big upper trough looks to evolve into more of a neutral tilt.

2. A surface low developing over SE Kansas / NE Oklahoma, which may help in locally backing surface winds.

How early the convection will develop on Tuesday, and resultant cloud cover and surface temps, will be important. However, it looks like a decent severe threat over Arkansas, which is notorious for January tornadoes. Goodness knows the wind fields look pretty favorable.

 

[Paul Redmond]

Impressive windfields, plenty of gulf moisture, Great for Arkansas and Norther LA, not so in east texas. Fast moving squall lines and some straight line winds. Armchair this event.