01/13/06: FCST: Midwest into the Gulf

[nickgrillo]

All models continue to point to amplification of the upper-air pattern by the late week... A strong shortwave will eject out and move out of the rockies and into the upper Mississippi valley by late THUR -- with surface cyclogenesis occuring ahead of the shortwave -- providing for synoptic-scale ascent impinging the warm sector by late THUR. This event REALLY looks like a ever-so-slightly less intense (thermodynamically speaking) version of last MON (amplifying H5 shortwave behind a sfc cyclone with storms initiating late night -- only to reintensify / redevelop by the afternoon in the lower OH valley and southward). At any rate, the combination of a strongly sheared troposphere and a moist boundary layer yields a favorable kinematic/thermodynamic environment for supercells and tornadoes across the warm sector (from MO / AR latenight THUR / early FRI and then points eastward as the front pushes east in the afternoon). Per the latest NAM, thinking that there is a pretty decent shot at tornadoes late night THUR / early FRI -- given at least a marginally unstable / very sheared boundary layer (with 0-3km SRH >300m2/s2 along the sfc trof by 12z FRI).

 

[Robert Dewey]

Well, I see there haven't really been any updates on the synoptic situation... So I guess I will jump in.

We currently have two camps - the further north and much weaker solution of the NAM and GFS... Versus the further south and much stronger solutions of the 00Z ECMWF, 12Z UKMET, and 12Z GEM. The further south solution would support the threat for severe weather development across the south - particularly south of the OH River. For example, the UKMET tracks a sfc low from southern IL to northeast OH... Deepening from 999MB to <989MB in about 12 hours while going negatively tilted at 500MB.

The ensembles currently support either solution, so you might as well just pick your favorite and go with it... Though the GFS and NAM have been slowly trending towards camp #2 (Euro models).