SPC AC 040549
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1249 AM CDT FRI APR 04 2008
VALID 041200Z - 051200Z
...THERE IS A SLGT RISK OF SVR TSTMS TODAY FROM PARTS OF ERN TEXAS
THROUGH MUCH OF THE CNTRL/PARTS OF THE ERN GULF STATES....
...SYNOPSIS...
MODELS SUGGEST THAT UPPER FLOW WILL BECOME BROADLY CYCLONIC ACROSS
MUCH OF THE U.S. TODAY...TO THE SOUTH OF A SIGNIFICANT CENTRAL
CANADIAN VORTEX...AND TO THE WEST OF AN AMPLIFYING WESTERN ATLANTIC
RIDGE. WITHIN THE CONFLUENT REGIME BETWEEN THESE TWO LARGE-SCALE
FEATURES...A LEAD SHORT WAVE IMPULSE...EMANATING FROM THE
SOUTHWEST...WILL LIKELY CONTINUE TO WEAKEN AND ACCELERATE
NORTHEASTWARD...ACROSS THE SOUTHERN GREAT LAKES AND NORTHEASTERN
STATES. AT THE SAME TIME...A SHORT WAVE TROUGH...WITHIN THE BELT OF
WESTERLIES EMANATING FROM THE NORTHERN PACIFIC...IS PROGGED TO
BECOME INCREASINGLY SHEARED AS IT PROGRESSES INTO/THROUGH THE OHIO
VALLEY. TRAILING THIS FEATURE...THE REMNANTS OF THE MAIN SOUTHERN
STREAM IMPULSE ARE FORECAST TO PIVOT EASTWARD ACROSS THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY.
IN RESPONSE TO THE EVOLVING UPPER PATTERN...THE PRIMARY SURFACE
FRONTAL WAVE IS FORECAST TO DEVELOP EAST NORTHEAST OF THE UPPER OHIO
VALLEY EARLY IN THE PERIOD. AND...THE ASSOCIATED SURFACE COLD FRONT
IS EXPECTED TO STEADILY ADVANCE TOWARD NORTHERN/MID ATLANTIC COASTAL
AREAS...WHILE LAGGING ACROSS THE LOWER MISSISSIPPI VALLEY THROUGH
MUCH OF THE DAY.
...WRN GULF COAST/LWR MS VALLEY INTO MID/SRN ATLANTIC SEABOARD...
BOUNDARY LAYER MODIFICATION MAY BEGIN TO OCCUR IN THE WAKE OF THE
RECENT COLD INTRUSION TO THE LEE OF THE CENTRAL/SOUTHERN
APPALACHIANS. BUT...THE REMNANTS OF ONGOING CONVECTION OVER THE
OHIO VALLEY ARE EXPECTED TO SPREAD AHEAD OF THE COLD FRONT AND
PROVIDE A STABILIZING INFLUENCE ACROSS THE MID ATLANTIC STATES
TODAY. MODELS ARE SUGGESTIVE THAT THE MOST SIGNIFICANT WARM SECTOR
DESTABILIZATION WILL BECOME FOCUSED ACROSS PARTS OF THE LOWER
MISSISSIPPI VALLEY/CENTRAL GULF STATES...WHERE HEATING OF A MOIST
BOUNDARY LAYER COUPLED WITH MODEST LAPSE RATES MAY YIELD CAPE IN
EXCESS OF 2000 J/KG.
INSTABILITY IS EXPECTED TO CONTRIBUTE TO VIGOROUS NEW CONVECTIVE
DEVELOPMENT...OR REINTENSIFICATION OF EARLY MORNING CONVECTIVE
ACTIVITY...SUPPORTED BY FORCING ASSOCIATED WITH THE SOUTHERN BRANCH
TROUGH...AS IT SPREADS INTO THE LOWER MISSISSIPPI VALLEY. THIS
COULD OCCUR AS EARLY AS 16-18Z...FROM PARTS OF EASTERN TEXAS INTO
NORTHERN MISSISSIPPI. AND...AS FORCING CONTINUES EASTWARD...THE
EVOLUTION OF A QUASI-LINEAR MESOSCALE CONVECTIVE SYSTEM APPEARS
POSSIBLE...PERHAPS PRECEDED BY A FEW MORE ISOLATED OR DISCRETE
STORMS.
GIVEN THE MAGNITUDE OF THE ANTICIPATED INSTABILITY...MODERATE DEEP
LAYER SHEAR...AND MOMENTUM ASSOCIATED WITH A 30-50 KT SOUTHWESTERLY
PRE-FRONTAL 850 JET...SHOULD CONTRIBUTE TO THE POTENTIAL FOR
DAMAGING WIND GUSTS...AND LARGE HAIL. AND...LOW- LEVEL SHEAR WILL
BE FAVORABLE FOR TORNADIC DEVELOPMENT... PARTICULARLY IN ANY
SUSTAINED DISCRETE STORMS.
A SEVERE THREAT IS EXPECTED TO PERSIST WITH ACTIVITY INTO EARLY
EVENING AS IT SPREADS THROUGH MUCH OF THE REMAINDER OF CENTRAL/
SOUTHERN MISSISSIPPI AND ALABAMA. BUT...THIS THREAT IS EXPECTED TO
WANE IN A MORE STABLE/STABILIZING ENVIRONMENT ACROSS THE EASTERN
GULF/SOUTH ATLANTIC COAST STATES DURING THE LATE EVENING/OVERNIGHT
HOURS.
..KERR/GRAMS.. 04/04/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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