Potential Severe Wed 2/15-Thur 2/16?

[tornadotony]

I'm not going to dive into specifics at this point because that would be incredibly pointless seven days out. But the long-range models have been consistently showing some signals that bear attention for severe potential around the middle of next week. All of them have been featuring general troughiness over the western U.S. and plains during this period, with ridging centered off the east coast. This is a very typical torching pattern for the central/eastern U.S. during winter months and a pattern that supports a wide open Gulf. The GFS/GEFS/Euro all hint at the potential for a shortwave trough/sfc cyclone to affect this region. To give some idea of what type of airmass might be accessible to a system next week, the 00z GFS already has 65F sfc dews all the way to Tuscaloosa next Thursday. That's pretty extraordinary for a week out on the GFS in February. It is by no means certain that a severe event is going to take place, but the chips seem to be in place early in the game and in enough places that it bears watching.

[andyhb]

Yeah, I've been on a bunch of forums watching this potential show up on the models for several days now, GFS has been the most consistent with the Euro not too far behind. One thing that is definitely likely is that the GoM is going to be in a prime state to supply a solid warm sector for any potential system like the models have been showing.

[Bryan Wood]

SPC concurs with your thoughts:

EARLY INDICATIONS ARE THAT A SEVERE THREAT COULD DEVELOP BY AROUND LATE DAY 6/TUESDAY INTO DAYS 7/8 WEDNESDAY/THURSDAY ACROSS THE SOUTH-CENTRAL CONUS...POTENTIALLY INCLUDING THE SOUTHERN PLAINS/ARKLATEX TO GULF COAST STATES AS CYCLOGENESIS OCCURS/MOISTURE RETURNS ACROSS THE REGION. HOWEVER...CONSIDERABLE UNCERTAINTY EXISTS AT THIS JUNCTURE.

What's interesting is that most GoMex water temps are from 2-5 degrees C above where they were this time last year.

[tornadotony]

http://www.spc.noaa.gov/products/outlook/day2otlk.html

[David Reimer]

A complicated setup for tomorrow from a chasing standpoint. I'll say off the bat that it's a marginal day. Heck, if it were any more marginal it would be nothing but a few rain showers. However, I'm seeing a few things that are keeping me interested in chasing tomorrow.

Hot off the 0Z North American Model (NAM) we have our Surface Based CAPE (Convective Available Potential Energy)...

These are always the hardest setups to forecast for regarding the possibility of severe weather. Instability values are quite marginal, even for a cool season event. Never the less, we do have some surface based instability at 3 PM on Wednesday. From the Red River south to about Madisonville, TX is a narrow corridor of instability values in excess of 500 joules per kilogram. South of Madisonville, our instability axis tends to widen out as we're closer to the gulf coast and higher amounts of moisture. Values are generally around 600 to 800 joules per kilogram. Those values are still marginal for cool season events, but just high enough that I believe there is some threat of organized, low-topped convection.

In lieu of a complete analysis of the wind fields, which I'll be publishing later on my website, I'll stick to the three kilometer Storm Relative Helicity Index. This graphic is also for 3 PM on Wednesday. Our primary low level jet will already be ejected off eastward into Louisiana and Arkansas, with a secondary area of westerly winds at 850 millibars in place across most of Central/East Texas. In terms of turning with height, forget about it. By tomorrow afternoon, everything looks quite linear across Texas. That's a different story across Louisiana and Southern Arkansas where low level winds are more southwesterly verses southerly. A few models have backed surface winds, creating pretty large hodographs in those areas. However, models continue to advertise little to no surface based instability in AR/LA, preventing any sort of surface-based convective threat.

However, there are two things I noticed on the 0Z NAM verses earlier runs. There seems to be slightly more instability across LA then earlier runs and wind shear seems to be lower across East Texas then earlier runs at 3 PM. At this time, I have two chase targets in mind if I were to go chasing tomorrow (which is a big if). My primary chase target would be close to the Gulf Coast in Southeast Texas. Instability values are higher and there's the possibility of mesoscale boundaries in place due to coastal effects (sea breeze, convective outflow, etc) that could briefly enhance updrafts and allow them to become briefly capable of producing a low level circulation. My second target is across Central/Northern Louisiana. My concern about heading out east is that models indicate widespread precipitation across those regions most of the afternoon hours, severely limiting instability and atmospheric recovery.

With all that said, I believe the severe weather threat for tomorrow is fairly marginal. If we can get elevated supercells to form later tonight and during the first half of Wedensday across North Texas and Oklahoma, there could be a decent hail threat due to increased instability values. After sunrise, instability values tend to decrease as upper forcing begins to eject northeastward and widespread convection forms thanks to warm air advection. I believe any afternoon severe weather threat will depend greatly on any localized areas of clearing, creating localized differential heating, along with any boundaries that may be in place. The 12Z High Resolution WRF indicated a QLCS type system forming across Southeast Texas. I wouldn't be shocked to see that occur. If that is the type of setup we deal with tomorrow, I would say there is a brief tornado threat with any QLCS spinup (much like we saw back a few weeks ago). Otherwise, spotty damaging winds and sub-severe hail would be the primary issues.

We'll see what happens overnight tonight and what the high resolution models say in a few hours. I don't expect tomorrow to be substantial, but after our event back in January, I'm going to expect the unexpected.

[tornadotony]

Yeah I'm not at all impressed. There is just nothing that stands out about tomorrow at all.