SWODY1
SPC AC 131944
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0244 PM CDT SUN MAY 13 2007
VALID 132000Z - 141200Z
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND TONIGHT OVER
PARTS OF THE NRN HIGH PLAINS...
..THERE IS A SLGT RISK OF SVR TSTMS MAINLY TONIGHT OVER PARTS OF
THE UPPER MS VALLEY INTO UPPER GREAT LAKES...
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON AND EVENING OVER
MUCH OF THE FL PENINSULA...
..NRN HIGH PLAINS...
COLD FRONT CONTINUES TO SLOWLY SAG SEWD THROUGH CNTRL MT EARLY THIS
AFTERNOON /W OF GGW-DLN LINE AS OF 19Z/ IN ADVANCE OF WELL DEFINED
SHORT WAVE TROUGH MOVING THROUGH ERN WA INTO THE ID PNHDL. THUS
FAR...TSTMS /MAINLY ELEVATED/ HAVE PERSISTED NEAR OR SLIGHTLY IN
POST-FRONTAL AIR MASS FROM HLN THROUGH HVR. MORE
VIGOROUS...SURFACE-BASED STORM DEVELOPMENT IS EXPECTED LATER THIS
AFTERNOON AHEAD OF FRONT OVER SWRN MT/NWRN WY WHERE INCREASED
LARGE-SCALE FORCING BEGINS TO ENCOUNTER A PROGRESSIVELY MORE
UNSTABLE AIR MASS.
THE PRESENCE OF STEEP LOW/MID-LEVEL LAPSE RATES AND 40-50 KT OF
EFFECTIVE BULK SHEAR INDICATE THE POTENTIAL FOR A FEW SUPERCELLS
AND/OR BOWING STRUCTURES CAPABLE OF LARGE HAIL...DAMAGING WINDS AND
PERHAPS A COUPLE TORNADOES. STORMS MAY GROW UPSCALE INTO CLUSTERS
OR AN MCS WITH A WIND/HAIL THREAT CONTINUING ACROSS ERN MT INTO THE
WRN DAKOTAS TONIGHT.
..UPPER MS VALLEY INTO UPPER GREAT LAKES...
LATEST MESOANALYSIS INDICATED A SURFACE LOW NE OF MBG WITH ATTENDANT
WARM FRONT EXTENDING NEWD TO N OF FAR AND THEN SSEWD THROUGH CNTRL
MN INTO WRN IA. AIR MASS S OF THIS WARM FRONT HAS WARMED WELL INTO
THE 80S ALREADY THIS AFTERNOON WITH DEWPOINTS COMMONLY IN THE 50S
WHICH WERE CONTRIBUTING TO MLCAPES OF 1000-2000 J/KG. HOWEVER...RUC
FORECAST SOUNDINGS INDICATE THAT CAP REMAINS QUITE STRONG ACROSS
WARM SECTOR.
OF INTEREST IS SOME ALTOCUMULUS ENHANCEMENT FROM JMS-FAR INVOF WARM
FRONT...IMMEDIATELY DOWNSTREAM FROM A WEAK MID-LEVEL IMPULSE
CRESTING MEAN RIDGE AXIS OVER WRN/CNTRL ND. CURRENT THINKING IS
THAT DEEP MOIST CONVECTION MAY BE DELAYED UNTIL LATER THIS EVENING
TO THE N OF WARM FRONT OVER FAR NRN MN AS STRONGER DEEP LAYER
FORCING FOR ASCENT ASSOCIATED WITH THIS IMPULSE BEGINS TO ACT ON A
MODERATELY UNSTABLE AIR MASS FOR ELEVATED PARCELS /MUCAPES OF
1000-2000 J PER KG/. MOST STORMS WILL LIKELY BE SLIGHTLY ELEVATED
WITHIN SUFFICIENTLY SHEARED ENVIRONMENT TO SUPPORT UPDRAFT ROTATION.
LARGE HAIL WILL BE THE PRIMARY SEVERE THREAT...THOUGH POTENTIAL WILL
EXIST FOR A TORNADO AND/OR LOCALLY DAMAGING WINDS SHOULD MORE
INTENSE STORMS BECOME ROOTED IN BOUNDARY LAYER.
STORMS WILL LIKELY MERGE INTO CLUSTERS WHILE MOVING/DEVELOPING SEWD
INTO THE UP OF MI OVERNIGHT.
..FL...
MODESTLY COOL MID-LEVEL TEMPERATURES COUPLED WITH A WARM AND MOIST
BOUNDARY LAYER IS RESULTING IN A MODERATELY UNSTABLE AIR MASS THIS
AFTERNOON ACROSS MUCH OF THE PENINSULA WITH MLCAPES OF 1000-1500
J/KG. TSTMS HAVE FORMED ON BOTH SEA BREEZE BOUNDARIES AS WELL AS
WEAK W-E ORIENTED COLD FRONT SLOWLY SHIFTING SWD THROUGH THE NRN
PENINSULA. WHILE VERTICAL SHEAR REMAINS RATHER WEAK...THERMODYNAMIC
ENVIRONMENT REMAINS SUPPORTIVE OF SEVERE HAIL AND LOCALLY DAMAGING
WIND GUSTS. IT APPEARS THE GREATEST WIND THREAT WILL EXIST WITH
ORGANIZING STORM CLUSTER NEAR OCF AS IT MOVES/PROPAGATES SWD THIS
AFTERNOON.
.MEAD.. 05/13/2007
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