3/7 - 3/8 FCST TX/OK/AR/LA

[Tom Dulong]

This is likely more a "wishcast" than forecast, but...

Based on latest GFS model:

* Fairly strong upper wave punching east across ArkLaTex region
* 55-60 deg F surface dewpoints advecting up from Gulf of Mexico
* Good 0-6 km shear based on surface/850mb/500mb winds
* Hint of 75-80 deg F advecting into area from south TX
* Chance of occurrence of any severe weather ramps up quickly for
ArkLaTex region next two weeks, based on NSSL data...at link

http://www.nssl.noaa.gov/hazard/tanim8094/...evanim8094.html

A squall line is more likely than supercells in the south this time of year, but there are always exceptions.

 

[Jeff Snyder]

Wishcast is a good descriptor...

The op GFS seems to be kicking the southwestern US upper low out much too quickly (refer to HPC Model Diagnostic discussion, many NWSFO discussion, etc.). The ECMWF, unlike the GFS, keeps a nice upper-levle low in the northern Baja area, with a huge trough in the eastern U.S.. Considering the model tendency to kick out low too quickly when located in the southwestern U.S., I prefer the slower solution, and thus I think this will be a big non-event (at least in terms of convective activity in the southern plains... Maybe something in the southeastern U.S. though, for the first time in a long time, if quality low-level moisture can advect into the region...

 

[Tom Dulong]

Timing is always an issue with cutoff lows. A slower movement would favor advecting better quality low level moisture into the southeast.

Originally posted by Jeff Snyder
Wishcast is a good descriptor...

Considering the model tendency to kick out low too quickly when located in the southwestern U.S., I prefer the slower solution, and thus I think this will be a big non-event (at least in terms of convective activity in the southern plains... Maybe something in the southeastern U.S. though, for the first time in a long time, if quality low-level moisture can advect into the region...

 

[Brett Adair]

Timing is going to be the biggest factor with this split flow setup currently given. I am not so sure areas will be able to destabalize rapidly enough to support any severe weather (especially in the southeast) due to below normal temperatures keeping a stable environment in tact. The GFS ensemble has backed off on the phasing solution with the NRN/SRN stream currently, but during this mid range cycle the GFS is not very good with kicking out energy in the southern stream.

 

[Robert Dewey]

As far as the phasing goes, the GFS actually has a bias of phasing northern/southern stream energy, when it should not (or too soon). Other medium range models (GEM, ECMWF, UKMET) also show a no-phase solution via the cutoff low and the northern stream system (0Z/MAR 3rd models). But, it is still more than several days out, and is subject to change obviously... If the system DOES phase, and happens faster than previous runs of the GFS, cyclogenesis will occur further west, if it happens too late (provided that it does happen), you may end up with an east coast storm.

NAO forecasts would favor a strong trough in the east, with a ridge in the west... Though, a ridge in the west doesn't mean a cutoff low couldn't exist, as seen on the GFS.

NAO:
http://www.cdc.noaa.gov/people/gary.bates/tele/nao.gif