SPC AC 070530
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 AM CDT THU MAY 07 2009
VALID 071200Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM OK/KS NEWD INTO THE WRN OH
VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS STRETCHING FROM THE MID
ATLANTIC STATES SEWD INTO THE GULF COAST STATES...
...SYNOPSIS...
WNWLY MID LEVEL WINDS AT 50-70 KT ARE FORECAST TO EXTEND FROM THE
PACIFIC NW INTO THE CENTRAL PLAINS AND EWD INTO THE MID ATLANTIC
STATES THROUGH THE PERIOD. WEAK EMBEDDED SHORTWAVE TROUGHS WILL
PROGRESS THROUGH THIS FLOW...THOUGH NONE OF THEM ARE FORECAST TO BE
STRONG ENOUGH TO RESULT IN HEIGHT FALLS OR AMPLIFY THE ZONAL FLOW.
AT THE SURFACE...A WEAK FRONT/REMNANT OUTFLOW BOUNDARY WILL LINGER
EAST OF THE APPALACHIANS SEWD INTO GULF COASTAL STATES. ANOTHER WEAK
COLD FRONT/TROUGH IS FORECAST TO EXTEND FROM THE WRN GREAT LAKES
SEWD INTO THE CENTRAL PLAINS BY LATE AFTERNOON.
...NRN/CENTRAL MO EWD INTO THE LOWER OH/TN VALLEYS...
SHORTWAVE TROUGH...WHICH WAS MOVING THROUGH WY WED EVENING...IS
FORECAST TO MOVE INTO NRN MO THU AFTERNOON AND INTO IL DURING THE
EVENING. LARGE SCALE LIFTING ASSOCIATED WITH THIS SYSTEM... COMBINED
WITH EFFECTIVE SHEAR AT 40-50 KT AND MLCAPES FROM 1000 TO 2000
J/KG...FAVOR ORGANIZED SEVERE CONVECTION DEVELOPING EWD THIS
AFTERNOON/EVENING FROM MO INTO THE WRN OH VALLEY. VEERING WINDS AND
STRONG 1 KM SHEAR MAY SUPPORT A TORNADO THREAT...ESPECIALLY ACROSS
PORTIONS OF MO...WHERE SURFACE DEWPOINTS SHOULD BE AT LEAST IN THE
MID 60S AND STRONG LOW LEVEL SHEAR WILL EXIST. HOWEVER... THE
PRIMARY SEVERE THREAT IS MORE LIKELY TO BE WIND DAMAGE...GIVEN THE
STRONGER FLOW ALOFT AND MOSTLY UNIDIRECTIONAL WLY FLOW ALOFT.
...SERN KS/SWRN MO/NRN AND CENTRAL OK/NWRN AR...
MOIST BOUNDARY LAYER...DEWPOINTS AOA 70F...AND AFTERNOON HEATING
WILL LEAD TO A VERY UNSTABLE AIRMASS...MLCAPES IN EXCESS OF 3000
J/KG. HOWEVER...LACK OF ANY EVIDENT DYNAMICAL FORCING AND STRONG
CAPPING BETWEEN 800 AND 700 MB WILL LIKELY INHIBIT STORM DEVELOPMENT
THROUGH THE DAYLIGHT HOURS. SHOULD ANY STORMS FORM... DEEP LAYER
SHEAR AND INSTABILITY WOULD BE SUPPORTIVE OF SUPERCELLS WITH VERY
LARGE HAIL. HOWEVER...THUNDERSTORMS ARE MORE LIKELY OVERNIGHT AS
BOUNDARY SAGS SLOWLY SEWD INTO FAR SERN KS/SWRN MO/NRN OK AND LOW
LEVEL JET/WARM ADVECTION INTENSIFIES. GIVEN THE DEGREE OF
INSTABILITY...30-40 KT MID LEVEL WNWLY FLOW AND SURFACE
BOUNDARY...AN MCS WITH HAIL AND BOWING SEGMENTS/WIND APPEARS
LIKELY...MAINLY AFTER 05Z.
...MID ATLANTIC STATES SEWD INTO THE GULF COASTAL STATES...
MODERATE INSTABILITY WILL OCCUR IN AREAS WHERE MOIST AIR MASS IS
WARMED FROM MORNING/EARLY AFTERNOON SUNSHINE. STORMS SHOULD READILY
DEVELOP DURING THE AFTERNOON ALONG A WEAK BOUNDARY LOCATED IN THE
REGION. MID LEVEL WLY WINDS AT 25 TO 40 KT WILL BE FAVORABLE FOR
MULTICELL SEVERE STORM CLUSTERS. LARGE HAIL AND DAMAGING WINDS
SHOULD BE THE PRIMARY SEVERE THREATS...DUE TO THE DEGREE OF
INSTABILITY AND MOSTLY UNDIRECTIONAL WLY FLOW ABOVE THE BOUNDARY
LAYER. STRONGER STORMS WILL BE DIURNALLY MODULATED... WITH ACTIVITY
EXPECTED TO DIMINISH AROUND SUNSET.
..IMY/JEWELL.. 05/07/2009
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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