SWODY1
SPC AC 211953
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0253 PM CDT THU MAY 21 2009
VALID 212000Z - 221200Z
...NO SVR TSTM AREAS FORECAST...
...FL...
VERY LITTLE CHANGE NEEDED OVER THE AREA. SURFACE CONVERGENCE ZONE
EXTENDING NNWWD FROM THE EVERGLADES TOWARDS THE TBW AREA HAS BECOME
PRIMARY AXIS OF STRONG THUNDERSTORM DEVELOPMENT THIS AFTERNOON.
APPEARS STORMS WILL REMAIN CAPABLE OF WET MICROBURSTS...AS WELL AS
BRIEF LANDSPOUT TORNADOES ALONG THIS FEATURE INTO THE EARLY EVENING.
OTHERWISE...OVERALL THREAT SHOULD DIMINISH THROUGH THE EVENING.
...SERN CO INTO WRN KS...
A FEW MORE ROBUST STORMS HAVE INTENSIFIED NEAR THE HIGHER TERRAIN
INVOF STALLED SURFACE FRONT OVER FAR SERN CO/NERN NM GIVEN INCREASED
LOW LEVEL CONVERGENCE AND MODEST INSTABILITY. SOME HAIL AND
POTENTIAL FOR A MICROBURST REMAINS POSSIBLE WITH THIS ACTIVITY...
ALTHOUGH STORMS MAY REMAIN ANCHORED NEAR THE HIGHER TERRAIN AND
COULD PRODUCE LOCALLY HEAVY RAINFALL. FARTHER NW...NARROW LINE OF
CU/TCU IS EVIDENT ALONG LEADING SURFACE TROUGH FROM FAR SERN CO INTO
N-CENTRAL KS AT 19Z. SHOULD A STORM DEVELOP...STEEP LOW LEVEL LAPSE
RATES WOULD FOSTER POTENTIAL FOR A STRONG DOWNBURST AND HAVE ADDED
CONDITIONAL LOW WIND PROBABILITIES ACCORDINGLY.
..EVANS.. 05/21/2009
.PREV DISCUSSION... /ISSUED 1107 AM CDT THU MAY 21 2009/
...SYNOPSIS...
A SUBTLE UPPER TROUGH MOVING THROUGH THE CNTRL CANADIAN PROVINCES
WILL SLOWLY MOVE EWD...GRADUALLY SHIFTING AN UPPER RIDGE JUST
OFFSHORE OF THE MID ATLANTIC EWD AS WELL. MEANWHILE AN UPPER LOW
OVER THE ERN GULF WILL SLOWLY DRIFT WWD AWAY FROM THE FL PENINSULA.
CONVERGENT BANDS ROTATING AROUND THE LOW MAY BE CONDUCIVE TO BRIEF
ROTATION. IN THE SOUTHWEST...WEAK UPPER DISTURBANCES WILL DRIFT NEWD
WITH PULSE THUNDERSTORMS AFFECTING A BROAD AREA.
...FLORIDA...
SEVERAL AREAS OF CONVERGENCE ARE NOTED ON VISIBLE SATELLITE IMAGERY
THIS MORNING...THAT WILL LIKELY PROVIDE A PRIMARY FOCUS FOR
WATERSPOUTS AND BRIEFLY ROTATING THUNDERSTORMS IN A VERY MOIST AND
UNSTABLE AIRMASS. THE MOST NOTABLE AREA OF CONVERGENCE AS OF 15Z
EXTENDS JUST OFFSHORE OF MIAMI NWWD TOWARDS TAMPA...AND MAY BE
REINFORCED BY AN OUTFLOW BOUNDARY FROM A NEARLY STATIONARY STORM
NEAR PALM BEACH. EXPECT PRIMARY THREAT TO BE OVER THE COASTAL WATERS
AND NEAR THE IMMEDIATE COAST...AS WEAK FLOW WILL BE CONDUCIVE TO
WATERSPOUTS. FARTHER N...A DIFFUSE WARM FRONT WILL DRIFT TOWARDS THE
PANHANDLE...WHILE ADDITIONAL CONVERGENT BANDS WILL ROTATE NWD AS
WELL. LOW LEVEL FLOW WILL REMAIN STRONGER ACROSS THESE AREAS...WITH
ENHANCED 0-3 KM DIRECTIONAL AND SPEED SHEAR SUPPORTING A FEW STORMS
WITH WEAK LOW LEVEL ROTATION. THIS WILL PRIMARILY BE A CONCERN BY
AFTERNOON AS THE ATMOSPHERE DESTABILIZES AND STORMS ENCOUNTER
ENHANCED BUOYANCY OF THE DIFFUSE WARM FRONT AND/OR AS LOCALIZED
CONVERGENCE AS BANDS DRIFT NWD.
...SOUTHWEST...
WEAK UPPER DISTURBANCES DRIFTING NEWD AND A MOIST/UNSTABLE AIRMASS
WILL INFLUENCE ANOTHER ROUND OF DIURNAL PULSE STORMS ACROSS A BROAD
AREA. WEAK LAPSE RATES AND UPPER FLOW SHOULD TEMPER THE SEVERE
THREAT...THOUGH ISOLD STORMS MAY BE CAPABLE OF HAIL/WIND GIVEN A
SUSTAINED UPDRAFT.
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