SWODY2
SPC AC 200546
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT FRI APR 20 2012
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS SATURDAY THROUGH SATURDAY NIGHT
ACROSS PARTS OF THE CENTRAL AND SOUTHERN FLORIDA PENINSULA...
...SYNOPSIS...
THE AMPLIFICATION OF AN UPPER RIDGE NOW APPEARS UNDERWAY NEAR THE
PACIFIC COAST STATES...AND...BY SATURDAY...THIS FEATURE IS EXPECTED
TO BECOME PROMINENT ACROSS MUCH OF THE WESTERN U.S. INTO WESTERN
CANADA. THE EVOLUTION OF THE DOWNSTREAM PATTERN REMAINS MORE
UNCERTAIN...AS MODELS INDICATE THAT SHORT WAVE IMPULSES WITHIN
BROADER SCALE TROUGHING EAST OF THE MISSISSIPPI VALLEY REMAIN OUT OF
PHASE.
ONE SIGNIFICANT IMPULSE...NOW IN THE PROCESS OF DIGGING INTO THE
SOUTHERN PLAINS...IS PROGGED TO REACH THE NORTHWEST GULF COAST
REGION BY 12Z SATURDAY...BEFORE TURNING EASTWARD TOWARD THE SOUTH
ATLANTIC COAST/FLORIDA PENINSULA DURING THE DAY. MODELS HAVE
EXHIBITED CONSIDERABLE VARIABILITY CONCERNING THIS FEATURE AND
ASSOCIATED LOW/MID-LEVEL CYCLOGENESIS ACROSS THE GULF COAST/
NORTHERN GULF OF MEXICO AND SOUTH ATLANTIC COAST REGION.
WITH THE EXCEPTION OF THE RISK FOR WIDELY SCATTERED THUNDERSTORM
ACTIVITY ACROSS PARTS OF THE NORTHERN GREAT BASIN...CONVECTIVE
POTENTIAL IS EXPECTED TO BE LOW ACROSS MUCH OF THE NATION
SATURDAY...IN THE WAKE OF A COLD FRONT LIKELY TO BE APPROACHING THE
APPALACHIANS BY THE BEGINNING OF THE PERIOD. AHEAD OF THE
FRONT...HOWEVER...CONSIDERABLE THUNDERSTORM ACTIVITY APPEARS
POSSIBLE ACROSS THE FLORIDA PENINSULA...AND PERHAPS ALONG THE
GEORGIA/CAROLINA PIEDMONT NORTHEASTWARD INTO NORTHERN MID ATLANTIC
COASTAL AREAS. SOME OF THIS ACTIVITY COULD BE SEVERE.
...CENTRAL/SOUTHERN FLORIDA PENINSULA...
GIVEN THE LARGE SPREAD THAT PERSISTS AMONG THE MODEL DATA...MUCH
UNCERTAINTY REMAINS CONCERNING CONVECTIVE POTENTIAL AND EVOLUTION ON
SATURDAY. GIVEN WEAK MID-LEVEL LAPSE RATES...AND PERHAPS
CONSIDERABLE CLOUD COVER...BOUNDARY LAYER CAPE MAY REMAIN WEAK TO
MODEST IN NATURE THROUGHOUT THE PERIOD. HOWEVER...MOST GUIDANCE
DOES INDICATE STRENGTHENING OF SOUTHERLY 850 MB FLOW IN EXCESS OF
30-40 KT BY SATURDAY NIGHT...IF NOT BEFORE...WITH THE APPROACH OF
THE UPPER IMPULSE. AS THIS OCCURS...IN THE PRESENCE OF A RELATIVELY
HIGH MOISTURE CONTENT AND NEARLY SATURATED LOW-LEVEL
ENVIRONMENT...ENLARGING...CLOCKWISE CURVED LOW-LEVEL HODOGRAPHS
PROBABLY WILL BECOME SUPPORTIVE OF ISOLATED SUPERCELLS CAPABLE OF
PRODUCING TORNADOES...LOCALIZED DAMAGING WIND GUSTS...POSSIBLY HAIL.
...CAROLINA PIEDMONT INTO NRN MID ATLANTIC COAST REGION...
MODELS SUGGEST THAT CONDITIONS AHEAD OF THE EASTWARD ADVANCING COLD
FRONT COULD BECOME CONDUCIVE TO VIGOROUS CONVECTIVE DEVELOPMENT
SATURDAY AFTERNOON AND EVENING. IF THIS OCCURS... SUB-CLOUD LAPSE
RATES ARE LIKELY TO BE STEEP WITH SIZABLE TEMPERATURE-DEW POINT
SPREADS. WHILE LOW-LEVEL FLOW MAY REMAIN WEAK...DEEP LAYER SHEAR
BENEATH MODERATE TO STRONG SOUTHWESTERLY MID/HIGH LEVEL FLOW
PROBABLY WILL BE AT LEAST MARGINALLY SUFFICIENT FOR ORGANIZED
CONVECTIVE DEVELOPMENT...WITH AT LEAST SOME WIND/SMALL HAIL
POTENTIAL.
..KERR.. 04/20/2012
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