DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 280555
SWODY1
SPC AC 280554

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1254 AM CDT TUE AUG 28 2012

VALID 281200Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PORTIONS OF THE
CENTRAL/NERN GULF COAST...

...SYNOPSIS...
TROPICAL STORM ISAAC IS FORECAST TO STRENGTHEN TO A HURRICANE AND
THE CENTER IS FORECAST TO MOVE ONSHORE ACROSS SERN LA TUESDAY
EVENING. SEE THE LATEST NHC FORECAST FOR DETAILS.

ELSEWHERE...A POSITIVELY TILTED UPPER LEVEL TROUGH WILL MOVE ONSHORE
ACROSS THE PACIFIC NW WHILE A BROAD UPPER TROUGH SHIFTS EWD ACROSS
NEW ENGLAND. HIGH PRESSURE ALOFT CENTERED OVER CO COVERS MUCH OF THE
AREA FROM THE PLAINS TO THE SOUTHWEST/SRN CA.

...GULF COAST ASSOCIATED WITH ISAAC...
AS ISAAC CONTINUES MOVING NORTHWEST...LOW-LEVEL WIND FIELDS WILL
STRENGTHEN SUBSTANTIALLY ALONG THE CENTRAL/NERN GULF COAST WHILE
LCLS REMAIN VERY LOW WITHIN A VERY MOIST AIR MASS. OUTER BANDS
APPROACHING THE COAST DURING THE MORNING WILL POSE AN ISOLATED
TORNADO RISK...AND THE THREAT WILL GRADUALLY SHIFT NWWD LATER IN THE
DAY AS ISAAC APPROACHES THE COAST.

DRIER AIR IN THE LOW-MID LEVELS TO THE EAST OF ISAAC...AND ALSO TO
THE NW AS SAMPLED BY 00Z RAOBS NEAR THE COAST AND INLAND...MAY
ULTIMATELY SERVE TO FOCUS/ENHANCE THE TORNADO THREAT AS THAT AIR
BECOMES WRAPPED AROUND THE CIRCULATION AS IT MOVES INLAND. THIS WILL
BE MONITORED AND PROBABILITIES ADJUSTED ACCORDINGLY IN LATER
OUTLOOKS.

...COASTAL NEW ENGLAND...
SOME DESTABILIZATION IS EXPECTED IN ADVANCE OF A COLD FRONT THAT
WILL MOVE OFFSHORE BY EARLY AFTERNOON. DESPITE THE TIMING...BELIEVE
POCKETS OF MLCAPE AS HIGH AS 1500 J/KG MAY DEVELOP ALONG WITH 40-50
KTS OF MID-LEVEL FLOW. FORCING FOR ASCENT ASSOCIATED WITH THE UPPER
LEVEL TROUGH AND FRONTAL CONVERGENCE SHOULD RESULT IN SCTD TSTM
DEVELOPMENT...WITH ISOLATED/WIDELY SCTD SVR WIND AND HAIL POSSIBLE
FOR A FEW HOURS PRIOR TO FRONTAL PASSAGE. FORECAST SOUNDINGS SHOW
MID-LEVEL DRYING DEVELOPING TOWARDS 18Z WHICH MAY SERVE TO AUGMENT
DOWNDRAFT STRENGTH.

...UPPER MIDWEST...
TSTMS MAY BE ON-GOING AT 12Z...WITH PRECIPITATION/REMNANT CLOUD
COVER PERSISTING BEYOND SUNRISE. A CONDITIONAL SVR THREAT WILL EXIST
LATER IN THE DAY IF SUFFICIENT HEATING/DESTABILIZATION CAN DEVELOP
IN THE VICINITY OF AN EAST-WEST FRONTAL BOUNDARY ACROSS SRN MN. NWLY
FLOW ALOFT WILL RESULT IN 40 KTS OF 0-6 KM SHEAR WHICH SHOULD BE
SUFFICIENT FOR ORGANIZED STORMS WITH AN ISOLATED WIND/HAIL THREAT.

..BUNTING/ROGERS.. 08/28/2012

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