SWODY1
SPC AC 241240
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 AM CDT SAT SEP 24 2011
VALID 241300Z - 251200Z
...NO SVR TSTM AREAS FORECAST...
...CAROLINAS...
CURRENT VAD DATA AND 12Z RAOBS INDICATE THAT A BELT OF 45-55 KT
SSWLY MIDLEVEL FLOW IS PRESENT ACROSS THE REGION THIS MORNING...
SIGNIFYING ERN ENVELOPE OF STRONGER WIND FIELD ATTENDANT TO
DEEP-LAYER CYCLONE OVER THE UPPER MIDWEST. EMBEDDED WITHIN THIS
FLOW REGIME...A SHORT-WAVE TROUGH CURRENTLY OVER THE CAROLINAS WILL
CONTINUE NNEWD TODAY WITH WEAKENING FORCING FOR ASCENT AND MIDLEVEL
WINDS IN ITS WAKE. IN THE LOW LEVELS...BAROCLINIC ZONE ANALYZED
ALONG THE PIEDMONT IS EXPECTED TO MOVE LITTLE THROUGH THE D1
PERIOD.
TSTMS HAVE PERSISTED EARLY THIS MORNING ACROSS PORTIONS OF CNTRL/ERN
SC AND CNTRL NC WITHIN A MOIST AIR MASS AND FORCED BY DCVA IN
ADVANCE OF MIDLEVEL IMPULSE. 12Z GSO/CHS SOUNDINGS INDICATE THAT
AIR MASS IS ALREADY MODERATELY UNSTABLE WITH MUCAPE VALUES OF
1500-2500 J/KG...AND BREAKS IN THE CLOUDS /PER VISIBLE SATELLITE
IMAGERY/ SHOULD ALLOW FOR FURTHER DESTABILIZATION THROUGH THIS
AFTERNOON. THE PRIMARY UNCERTAINTY IS WHAT EFFECT THE EARLY PASSAGE
OF SHORT-WAVE TROUGH WILL HAVE ON TSTM COVERAGE/INTENSITY THIS
AFTERNOON WHEN AIR MASS BECOMES MORE UNSTABLE. IN ANY EVENT...
CURRENT OBSERVATIONAL DATA SHOW THAT SUFFICIENT SHEAR AND
INSTABILITY ALREADY EXISTS FOR PERSISTENT STORM STRUCTURES /MARGINAL
SUPERCELLS/ WITH A RISK FOR LOCALLY DAMAGING WET MICROBURSTS AND
PERHAPS A BRIEF TORNADO.
...OH VALLEY...
WEAK SURFACE LOW ANALYZED NEAR THE IL/IND BORDER WILL SLOWLY DEVELOP
WWD TODAY IN CONJUNCTION WITH THE DEEP-LAYER CIRCULATION. DESPITE
THE EQUIVALENT-BAROTROPIC NATURE OF SYNOPTIC SYSTEM...A BELT OF
40-60 KT MIDLEVEL FLOW WILL BE MAINTAINED AROUND PERIPHERY OF
CIRCULATION ALONG WITH 500-MB TEMPERATURES AOB -20 C. GIVEN THE
CO-LOCATION OF MIDLEVEL LAPSE RATES OF AROUND 7 C/KM AND VERTICALLY
VEERING WIND PROFILES WITH 40-50 KT OF DEEP-LAYER SHEAR...SOME
POTENTIAL FOR SEVERE STORM FORMATION WILL EXIST. HOWEVER...LATEST
MODEL GUIDANCE REMAINS CONSISTENT IN SUGGESTING THE BOUNDARY LAYER
WILL REMAIN TOO COOL AND DRY TO SUPPORT ANY MEANINGFUL INSTABILITY.
AS SUCH...NO SEVERE WEATHER PROBABILITIES WILL BE INCLUDED IN THIS
FORECAST.
..MEAD/ROGERS.. 09/24/2011
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