SWODY2
SPC AC 241716
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
ISSUED BY 15TH OWS SCOTT AIR FORCE BASE IL
1216 PM CDT THU SEP 24 2009
VALID 251200Z - 261200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
MIDLEVEL LOW WHICH HAS REMAINED ANCHORED OVER THE CNTRL PLAINS WILL
BEGIN TO SHIFT EWD DURING THE DAY TWO PERIOD IN RESPONSE TO THE
APPROACH OF A STRONG UPPER JET STREAK THROUGH THE NERN PACIFIC INTO
WRN CANADA. THIS LOW WILL GRADUALLY MOVE TO THE N OF MID/UPPER HIGH
RETROGRADING WWD THROUGH FL INTO THE ERN GULF OF MEXICO.
AT THE SURFACE...A WEAK CYCLONE ASSOCIATED WITH UPPER LOW WILL
DEVELOP EWD THROUGH THE MID MO VALLEY...WHILE FARTHER E...BAROCLINIC
ZONE SITUATED ALONG THE MS RIVER VALLEY SHIFTS SLOWLY EWD. AN E-W
ORIENTED WARM FRONTAL SEGMENT WILL INTERSECT THIS FORMER BAROCLINIC
ZONE OVER THE MID MS VALLEY...BEFORE EXTENDING EWD THROUGH MUCH OF
THE OH VALLEY. THE SERN EXTENSION OF THIS BOUNDARY WILL ASSUME MORE
WEDGE FRONT OR "BACKDOOR" COLD FRONTAL PROPERTIES WHILE SAGGING SWD
THROUGH THE CNTRL/SRN PIEDMONT AND COASTAL PLAINS.
...NEB/KS...
WARM SECTOR AIR MASS DESTABILIZATION WILL BE LIMITED FRIDAY DUE TO
CONSIDERABLE CLOUDINESS AND RELATIVELY DRY BOUNDARY LAYER CONDITIONS
/I.E. DEWPOINTS LARGELY IN THE 40S/ WITH MLCAPE GENERALLY LESS THAN
500 J/KG. NONETHELESS...DEEP FORCING ASSOCIATED WITH UPPER SYSTEM
SHOULD SUPPORT SCATTERED TSTM DEVELOPMENT BY AFTERNOON FROM VICINITY
OF THE SURFACE LOW OVER NEB SWWD ALONG FRONT INTO WRN/CNTRL PARTS OF
KS.
VERTICAL SHEAR WILL REMAIN RATHER WEAK OVER NEB INTO NRN KS /OWING
TO CLOSE PROXIMITY OF CIRCULATION CENTER/...BEFORE INCREASING TO
30-40 KT THROUGH 6 KM ACROSS CNTRL/SRN KS. GIVEN THE RELATIVELY
COOL THERMODYNAMIC PROFILES...HAIL APPEARS TO BE THE PRIMARY THREAT
WITH THE STRONGEST STORMS. HOWEVER...SHOULD STRONGER SURFACE
HEATING OCCUR...A BRIEF TORNADO OR TWO REMAINS POSSIBLE NEAR SURFACE
LOW WHERE AMBIENT VERTICAL VORTICITY WILL BE GREATEST.
WILL MAINTAIN ONLY LOW SEVERE PROBABILITIES DUE TO ABOVE-MENTIONED
CONCERNS REGARDING AIR MASS DESTABILIZATION.
...LOWER MS/TN/OH VALLEYS...
SIMILAR TO THE CNTRL PLAINS...IT APPEARS CLOUDS WILL LIMIT DIABATIC
HEATING...PARTICULARLY ACROSS PARTS OF THE OH AND TN VALLEYS.
FARTHER S...BOUNDARY LAYER DEWPOINTS IN THE 70S AND COMPARATIVELY
STRONG HEATING WILL CONTRIBUTE TO POCKETS OF MODERATE INSTABILITY
WITH MLCAPE APPROACHING 1000-1500 J/KG. GIVEN THE RELATIVELY WEAK
CAPPING...EXPECT A GENERAL INCREASE IN STORM COVERAGE THROUGH THE
DAY IN AREAS WHERE THE STRONGER DESTABILIZATION OCCURS.
MODEL GUIDANCE CONTINUES TO SUGGEST THAT STRONGER WIND FIELD
ASSOCIATED WITH UPPER LOW WILL LAG PRIMARY INSTABILITY AXIS TO THE
W/NW WITH ONLY MARGINAL VERTICAL SHEAR /I.E. 25-30 KT THROUGH 6 KM/
EXPECTED ACROSS WARM SECTOR THROUGH THE DIURNAL HEATING CYCLE. THIS
WILL TEND TO LIMIT THE POTENTIAL FOR A MORE ORGANIZED SEVERE WEATHER
THREAT...THOUGH ISOLATED...STRONG TO MARGINALLY SEVERE STORMS WILL
REMAIN POSSIBLE.
LLJ DEVELOPMENT FRIDAY NIGHT IS NOW NOT AS PRONOUNCED AS IN PREVIOUS
MODEL RUNS...WHICH SHOULD LIMIT THE NWD EXTEND OF AN MEANINGFUL AIR
MASS DESTABILIZATION TO THE OH RIVER. MOREOVER...INCREASING
CONVECTIVE INHIBITION ACROSS WARM SECTOR WILL MITIGATE THE POTENTIAL
FOR ANY MORE ROBUST NOCTURNAL SEVERE THREAT.
..15_OWS.. 09/24/2009
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