DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 311251
SWODY1
SPC AC 311249

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0749 AM CDT FRI AUG 31 2012

VALID 311300Z - 011200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING FOR NRN
NY AND NRN NEW ENGLAND...

...THERE IS A SLGT RISK OF SVR TSTMS TODAY FOR THE ERN AR/SE MO
AREA...

...NRN NEW ENGLAND TODAY...
A MIDLEVEL SHORTWAVE TROUGH OVER JAMES BAY...AND OTHER LEAD SPEED
MAXIMA...WILL PROGRESS ESEWD OVER NRN NEW ENGLAND BY THIS
AFTERNOON/EVENING...ACCOMPANIED BY A SURFACE COLD FRONT. A NARROW
CORRIDOR OF LOW-MID 60S BOUNDARY LAYER DEWPOINTS WILL OVERSPREAD THE
SAINT LAWRENCE VALLEY AND NRN NEW ENGLAND FROM SRN ONTARIO/QUEBEC IN
ADVANCE OF THE COLD FRONT...ALONG WITH THE ERN EXTENT OF A MIDLEVEL
LAPSE RATE PLUME ORIGINATING OVER THE NRN ROCKIES/PLAINS. AFTERNOON
SURFACE TEMPERATURES WARMING TO AOA 80 F IN CLOUD BREAKS...WITH THE
AFOREMENTIONED MOISTURE/LAPSE RATES... WILL RESULT IN MLCAPE VALUES
OF 500-1000 J/KG.

THERE IS SOME UNCERTAINTY REGARDING THE IMPACT OF CLOUD COVER ON
SURFACE HEATING THIS AFTERNOON...THOUGH BROKEN BANDS OF
THUNDERSTORMS ARE EXPECTED TO DEVELOP AROUND 19-22Z AND MOVE INTO
NRN NY/NRN NEW ENGLAND AS ASCENT ALONG THE FRONT PHASES WITH THE
DIURNAL HEATING CYCLE. THE SEVERE RISK SHOULD PERSIST UNTIL ABOUT
02Z. DEEP-LAYER WNWLY SHEAR /EFFECTIVE BULK WIND DIFFERENCES AOA 50
KT/ WITH STRAIGHT HODOGRAPHS WILL FAVOR BOTH SUPERCELLS AND SHORT
BOWING SEGMENTS...WITH AN ACCOMPANYING RISK FOR LARGE HAIL AND
DAMAGING WINDS. AN ISOLATED TORNADO CANNOT BE RULED OUT...THOUGH
LOW-LEVEL SHEAR/MOISTURE/BUOYANCY WILL ALL BE SOMEWHAT MARGINAL FOR
A SUSTAINED TORNADO THREAT.

...ERN AR/MO TODAY WITH REMNANTS OF TC ISAAC...
THE CORE REMNANTS OF TROPICAL CYCLONE ISAAC ARE MOVING GENERALLY NWD
OVER WRN AR THIS MORNING...AND THIS MOTION SHOULD CONTINUE THROUGH
TONIGHT INTO SW/W CENTRAL MO. E OF THE CYCLONE CORE...THERE WILL BE
A NARROW ZONE OF OVERLAP BETWEEN ENHANCED LOW-LEVEL SHEAR AND THE NW
EDGE OF THE MORE SUBSTANTIAL SURFACE-BASED BUOYANCY. HERE...A FEW
ROTATING STORMS WILL AGAIN BE POSSIBLE WITHIN THE OUTER ERN BANDS
ACROSS AR/MO...PRIMARILY THIS AFTERNOON WHEN OCCASIONAL CLOUD BREAKS
LOCALLY BOOST INSTABILITY. CONTINUED INLAND MOVEMENT AND GRADUAL
WEAKENING OF THE SYSTEM SUGGEST THAT THE TORNADO RISK IS BECOMING
MORE DIURNAL AND MARGINAL WITH TIME.

..THOMPSON/ROGERS.. 08/31/2012

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