SPC AC 201632
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1132 AM CDT SUN AUG 20 2006
VALID 201630Z - 211200Z
...THERE IS A SLGT RISK OF SVR TSTMS OVER SRN NEW ENGLAND...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF THE DAKOTAS...
...NRN PLAINS...
SURFACE COLD FRONT NOW EXTENDING FROM MANITOBA SEWD INTO NERN MT
WILL CONTINUE SSEWD INTO THE CENTRAL DAKOTAS BY LATER TODAY/THIS
EVENING. AHEAD OF WHICH...STRONG HEATING WILL OCCUR WITHIN NRN EDGE
OF NEAR 60F SURFACE DEW POINTS. EXPECT 55-60F SURFACE DEW POINTS
WILL SURVIVE DIURNAL MIXING AND ALLOW AXIS OF MODERATE INSTABILITY
TO DEVELOP ACROSS THIS REGION BY LATE IN THE AFTERNOON. RUC PFC/S
INDICATE MLCAPE MAY EXCEED 2000 J/KG BY 00Z. REGION WILL ALSO
REMAIN ALONG FRINGE OF MODEST WLY FLOW ALOFT AND SUPPORT 30-40 KT
EFFECTIVE SHEAR LATER TODAY AND THIS EVENING. THEREFORE...SEVERE
POTENTIAL SHOULD INCREASE BY THE LATE AFTERNOON AS CINH DIMINISHES
ALONG AND AHEAD OF APPROACHING SURFACE FRONT/TROUGH. ACTIVITY WILL
LIKELY DEVELOP AROUND 21Z AND ORGANIZE INTO SUPERCELLS/LINES AS
STORMS SHIFT ESEWD THROUGH THE EVENING. MARGINAL LOW LEVEL
FLOW/SHEAR ALONG WITH RELATIVELY HIGH LCLS INDICATE PRIMARY THREATS
WILL BE FROM DAMAGING WINDS AND LARGE HAIL.
...NEW ENGLAND...
LOW LEVEL AIR MASS REMAINS QUITE MOIST ACROSS SRN NEW ENGLAND EARLY
THIS AFTERNOON WITH SURFACE DEW POINTS IN THE LOWER 70S. THIS IS
OCCURRING WITHIN MID LEVEL DRY SLOT IN WAKE OF WEAK MID LEVEL
IMPULSE NOW SHIFTING OVER THE NEW ENGLAND COAST. EXPECT LOW LEVEL
FLOW WILL BECOME INCREASINGLY WSWLY THROUGH THE DAY AND LIMIT
OVERALL CONVERGENCE ACROSS THE AREA. HOWEVER...STRONG HEATING AND
DEGREE OF BOUNDARY LAYER MOISTURE SHOULD ALLOW MODEST INSTABILITY TO
DEVELOP DESPITE THE RATHER WEAK LAPSE RATES IN PLACE. IF STORMS CAN
REFORM WITHIN DESTABILIZING AIR MASS...ISOLATED DAMAGING WINDS MAY
OCCUR GIVEN AMOUNT OF WLY FLOW IN THE LOW TO MID TROPOSPHERE AND
STEEPENING LOW LEVEL LAPSE RATES...ALONG WITH SOME HAIL. OVERALL
THREAT SHOULD DIMINISH QUICKLY AFTER DARK THIS EVENING.
...OZARKS/MID MS VALLEY...
A COLD FRONT WILL ADVANCE SWD ACROSS THE REGION TODAY PROVIDING A
FOCUS FOR CONVECTIVE DEVELOPMENT THIS AFTERNOON. ALTHOUGH VERTICAL
SHEAR WILL BE RELATIVELY WEAK...MODERATE INSTABILITY IS ALREADY IN
PLACE ACROSS PARTS OF AR AND TN WHERE OBJECTIVE ANALYSIS ESTIMATES
MLCAPE VALUES IN THE 1000 TO 1500 J/KG. AS INSTABILITY INCREASES AND
LOW-LEVEL LAPSE RATES STEEPEN THIS AFTERNOON...THE STRONGER
THUNDERSTORMS MAY BE CAPABLE OF STRONG WIND GUSTS ESPECIALLY AROUND
PEAK HEATING LATE THIS AFTERNOON.
...ERN SEABOARD...
AN UPPER-LEVEL TROUGH WILL MOVE INTO THE CNTRL APPALACHIANS TODAY AS
A COLD FRONT ADVANCES SEWD INTO THE CAROLINAS. MODEL FORECASTS SHOW
STRONG LOW-LEVEL CONVERGENCE ALONG THE FRONT WHICH SHOULD RESULT IN
SCATTERED THUNDERSTORM INITIATION BY EARLY AFTERNOON. MODERATE TO
STRONG INSTABILITY IS FORECAST TO DEVELOP ALONG WITH VERY STEEP
LOW-LEVEL LAPSE RATES WHICH SHOULD BE FAVORABLE FOR STRONG GUSTY
WINDS. HOWEVER...WEAK VERTICAL SHEAR PROFILES SHOULD KEEP ANY SEVERE
THREAT THAT DEVELOPS FAIRLY ISOLATED.
..EVANS/CROSBIE.. 08/20/2006
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z
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