SWODY1
SPC AC 181221
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0721 AM CDT SUN APR 18 2010
VALID 181300Z - 191200Z
...NO SVR TSTM AREAS FORECAST...
...SRN FL PENINSULA...
SRN STREAM SHORTWAVE TROUGH NOW APPROACHING SW FL WILL CONTINUE
ENEWD AND SLOWLY LOSE AMPLITUDE TODAY AS IT SHIFTS ACROSS THE SRN FL
PENINSULA...WHILE ANOTHER LOW AMPLITUDE WAVE MOVES ACROSS THE GULF
OF MEXICO TONIGHT. MODEL GUIDANCE SUGGESTS A WEAK SURFACE LOW WILL
DEVELOP AND MOVE OVER OR NEAR SRN FL LATER TODAY AND TONIGHT. AIR
MASS WILL REMAIN DEEPLY MOIST WITH VERY WEAK LAPSE RATES THROUGH THE
PERIOD...GREATLY LIMITING OVERALL INSTABILITY DESPITE PRESENCE OF
MID 60S-LOWER 70S F SURFACE DEW POINTS. HOWEVER...INCREASED FORCING
FOR ASCENT ATTENDANT TO APPROACHING MIDLEVEL SYSTEM IN CONJUNCTION
WITH DEVELOPING SEA BREEZE CIRCULATIONS ARE EXPECTED TO FOSTER
SCATTERED TO NUMEROUS DIURNAL STORMS WITHIN THE MOIST AND WEAKLY
CAPPED ENVIRONMENT. MASS RESPONSE TO WEAK SURFACE LOW UNDER MODEST
WSWLY MID LEVEL FLOW SHOULD SUPPORT EFFECTIVE SRH IN EXCESS OF 150
M2/S2 BY THE EARLY EVENING...ALONG WITH 30-40 KT EFFECTIVE BULK
SHEAR. THIS SHOULD SUPPORT AT LEAST LOW POTENTIAL FOR
EMBEDDED/TRANSIENT SUPERCELLS CAPABLE OF LOCALLY STRONG WINDS AND
PERHAPS A BRIEF TORNADO. THIS SEVERE THREAT WILL LIKELY PERSIST
OVERNIGHT IN ASSOCIATION WITH ISOLATED/SCATTERED STORMS WHICH MAY
DEVELOP IN ADVANCE OF THE SURFACE LOW.
...HIGH PLAINS...
DESPITE THE PRESENCE OF A RELATIVELY DRY BOUNDARY LAYER...STEEP LOW-
TO MIDLEVEL LAPSE RATES WILL CONTRIBUTE TO A WEAKLY UNSTABLE AIR
MASS BY AFTERNOON WHERE MLCAPE MAY APPROACH 500-700 J/KG. MIDLEVEL
HEIGHTS WILL REBOUND SLIGHTLY THROUGH THE DAY IN THE WAKE OF
MIDLEVEL IMPULSE SLOWLY TRANSLATING EWD INTO THE DAKOTAS AND NEB.
NONETHELESS...ISOLATED DIURNAL STORMS APPEAR LIKELY OWING TO THE
COMBINATION OF TERRAIN INFLUENCES AND CONVERGENCE ALONG SURFACE
BOUNDARY STALLED IN THE LEE OF THE HIGHER TERRAIN. THE STRONGER
STORMS WILL BE CAPABLE OF SOME SMALL HAIL...THOUGH THE PROSPECT FOR
SEVERE WEATHER APPEARS QUITE SMALL AT THIS TIME.
...TX/LA COAST...
SCATTERED THUNDERSTORMS WILL PERSIST FOR MUCH OF THE PERIOD AS SRN
STREAM IMPULSE LOSES AMPLITUDE ACROSS THIS AREA. HOWEVER...MODEST
INSTABILITY WILL ONCE AGAIN BE COMMON /DESPITE WEAK LAPSE RATES/
WHICH SHOULD SUSTAIN DEEP MOIST CONVECTION AND SCATTERED
THUNDERSTORMS. OVERALL...SEVERE THREAT SHOULD REMAIN QUITE LOW.
ALTHOUGH...A FEW MORE ROBUST STORMS WILL BE CAPABLE OF PRODUCING
STRONG GUSTS.
..EVANS/STOPPKOTTE.. 04/18/2010
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