SPC AC 211622
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CDT MON MAR 21 2011
VALID 211630Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF THE UPPER OH
VALLEY...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE MIDWEST...
A BROAD UPPER RIDGE IS SLOWLY BUILDING ACROSS THE GULF COAST AND
SOUTHERN PLAINS TODAY...WITH A STRONG SHORTWAVE TROUGH ROTATING INTO
CA/NV. SOUTHERLY LOW LEVEL WINDS ARE WIDESPREAD TODAY SOUTH OF THE
MAIN BAROCLINIC ZONE FROM THE DAKOTAS INTO THE OH VALLEY...BUT AN
ONLY PARTIALLY MODIFIED AIR MASS OVER THE GULF OF MEXICO HAS LIMITED
SURFACE DEWPOINT VALUES TO THE 50S AND LOWER 60S OVER MOST OF THIS
REGION. NEVERTHELESS...THE CORRIDOR FROM SD/NEB INTO THE MID
ATLANTIC STATES WILL HAVE A RISK OF SCATTERED THUNDERSTORMS /SOME
SEVERE/ THIS AFTERNOON AND TONIGHT.
...OH/KY/WV/PA...
RATHER STRONG WEST-NORTHWESTERLY MID LEVEL WINDS ARE PROGD THIS
AFTERNOON OVER THE OH VALLEY AND CENTRAL APPALACHIANS /500MB WINDS
OF 60-70 KT/. MEANWHILE...THE PRIMARY SURFACE FRONT EXTENDS FROM
LAKE ERIE SOUTHWESTWARD INTO CENTRAL IND/IL. PARTIAL SUNSHINE AND
SURFACE DEWPOINTS IN THE 50S WILL YIELD AFTERNOON MLCAPE VALUES OF
500-1000 J/KG AHEAD OF THE FRONT. MOST MODEL SOLUTIONS AGREE IN THE
DEVELOPMENT OF SCATTERED THUNDERSTORMS LATER THIS AFTERNOON ALONG
THE FRONT AS IT SAGS INTO SOUTHERN OH. FORECAST SOUNDINGS SHOW
STEEP MID LEVEL LAPSE RATES AND 30-40 KNOTS OF EFFECTIVE SHEAR.
THIS SUGGESTS A RISK OF HAIL AND DAMAGING WINDS IN THE STRONGER
CELLS THROUGH EARLY EVENING AS STORMS SPREAD INTO PORTIONS OF KY/WV
AND SOUTHWEST PA. WEAKER LOW LEVEL MOISTURE/INSTABILITY FARTHER
EAST OVER VA WILL LIKELY LIMIT CONVECTIVE POTENTIAL...BUT A
CONDITIONAL RISK OF HAIL WILL BE PRESENT IF STORMS CAN CROSS THE
MOUNTAINS THIS EVENING.
...SD/NEB/IA/MN...
AS THE UPPER RIDGE BUILDS ACROSS THE SOUTHERN/CENTRAL PLAINS
TODAY...STRONG SOUTHERLY LOW LEVEL WINDS WILL TRANSPORT 50S TO LOWER
60S DEWPOINTS NORTHWARD INTO KS/MO AND EVENTUALLY SOUTHERN NEB.
HOWEVER...MORNING RAOBS CONFIRM A STRONG CAPPING INVERSION OVER THE
WARM SECTOR THAT WILL LIKELY INHIBIT DEEP CONVECTION THROUGH MOST OF
THE PERIOD. AFTER 00Z...IT APPEARS LIKELY THAT A COMBINATION OF LOW
LEVEL WARM ADVECTION AND SUBTLE MID LEVEL HEIGHT FALLS WILL HELP TO
INITIATE SCATTERED THUNDERSTORMS NORTH OF THE WARM FRONT OVER
SD/NEB/IA. FORECAST SOUNDINGS SHOW FAVORABLE THERMODYNAMIC AND
KINEMATIC PROFILES FOR ELEVATED SUPERCELLS CAPABLE OF LARGE HAIL.
ACTIVITY WILL LIKELY PERSIST THROUGH THE NIGHT AND DRIFT
EAST-NORTHEASTWARD INTO NORTHERN IA/SOUTHERN MN. AT THIS
TIME...WARM SECTOR DEVELOPMENT /SURFACE-BASED STORMS/ APPEARS
UNLIKELY OVER SOUTHERN NEB/NORTHERN KS.
..HART/COHEN.. 03/21/2011
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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