SWODY1
SPC AC 131229
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0729 AM CDT MON SEP 13 2010
VALID 131300Z - 141200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE CENTRAL
PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS FROM NY INTO SOUTHERN NEW
ENGLAND...
...CENTRAL PLAINS...
A LOW-AMPLITUDE UPPER RIDGE WILL REMAIN IN PLACE OVER THE SOUTHERN
ROCKIES AND SOUTHEAST STATES TODAY...WHILE MODERATELY FAST WESTERLY
FLOW ALOFT AFFECTS THE CENTRAL/NORTHERN SECTIONS OF THE COUNTRY.
SOUTHERLY LOW LEVEL WINDS OVER THE PLAINS WILL HELP TO TRANSPORT
GULF MOISTURE NORTHWARD TODAY...LEADING TO MODERATE AFTERNOON
INSTABILITY ACROSS PORTIONS OF KS/NEB/SD. DESPITE THE RELATIVELY
LACK OF MID/UPPER LEVEL FORCING MECHANISMS...MOST MODEL GUIDANCE IS
IN AGREEMENT THAT ISOLATED TO SCATTERED THUNDERSTORMS WILL FORM
DURING PEAK HEATING FROM NORTH CENTRAL KS INTO SOUTHEAST SD.
FORECAST SOUNDINGS SHOW STEEP LOW/MID LEVEL LAPSE RATES AND
SUFFICIENT CAPE /1500-2000 J/KG MLCAPE/ FOR ROBUST UPDRAFTS.
VERTICAL SHEAR WILL ALSO BE SUFFICIENT FOR SUPERCELL STORM
STRUCTURES. LARGE HAIL AND DAMAGING WINDS ARE LIKELY TO BE THE MAIN
THREATS...ALTHOUGH AN ISOLATED TORNADO CANNOT BE RULED OUT. STORMS
WILL DEVELOP EASTWARD AFTER DARK INTO WESTERN/CENTRAL IA AS LOW
LEVEL JET STRENGTHENS AND ENHANCES FORCING.
...NEW YORK INTO SOUTHERN NEW ENGLAND...
MORNING WATER VAPOR IMAGERY SHOWS AN UPPER LEVEL TROUGH MOVING
ACROSS THE GREAT LAKES REGION. ONE SHORTWAVE TROUGH EMBEDDED IN THE
LARGER SCALE CYCLONIC FLOW IS OVER LOWER MI/SOUTHERN ONT. THIS
FEATURE WILL TRACK EASTWARD ACROSS NY TODAY AND INTO SOUTHERN NEW
ENGLAND THIS EVENING. DEWPOINTS IN THE 50S...BREAKS IN THE
CLOUDS...AND COOLING TEMPERATURES ALOFT WILL HELP TO YIELD POCKETS
OF MODEST INSTABILITY. FORECAST SOUNDINGS SUGGEST MLCAPE OF AROUND
500 J/KG. IT APPEARS LIKELY THAT THE SMALL CLUSTER OF THUNDERSTORMS
NOW NEAR BUF WILL BE MAINTAINED AT TRACK ACROSS THE SLIGHT RISK AREA
THROUGH THE DAY. DEEP LAYER EFFECTIVE SHEAR OF 30-35 KNOTS
INDICATES THE POTENTIAL FOR A FEW ORGANIZED STORMS CAPABLE OF HAIL
AND DAMAGING WINDS. THREAT SHOULD DIMINISH QUICKLY AFTER SUNSET.
..HART/STOPPKOTTE.. 09/13/2010
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