MESO: Mesoscale Discussion 0384

ACUS11 KWNS 040814
SWOMCD
SPC MCD 040813
FLZ000-041045-

MESOSCALE DISCUSSION 0384
NWS STORM PREDICTION CENTER NORMAN OK
0313 AM CDT THU APR 04 2013

AREAS AFFECTED...PORTIONS SWRN FL.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 040813Z - 041045Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...BAND OF TSTMS MAY AFFECT PORTIONS COASTAL SWRN FL BETWEEN
830-12Z...BEGINNING NEAR SRQ AND AFFECTING AREAS SWD TOWARD
SANIBEL...FMY AND PERHAPS APF/MARCO AREA WITH TIME. ISOLATED STG
GUSTS AND HAIL NEAR SVR LIMITS ARE POSSIBLE. MRGL NATURE AND
LIMITED SPATIAL EXTENT OF THREAT INDICATE WW IS NOT LIKELY TO BE
REQUIRED.

DISCUSSION...SFC MESOANALYSIS SHOWS QUASISTATIONARY/SYNOPTIC FRONT
ACROSS NRN FL EXTENDING INTO FRONTAL-WAVE LOW JUST SW AAF. WELL S
OF THAT...DIFFUSE OUTFLOW BOUNDARY WAS DRAWN FROM NEAR MLB WWD
ACROSS NRN PORTIONS TAMPA BAY AREA THEN NWWD ACROSS GULF INTO LOW.
SFC TROUGH AND CORRESPONDING WIND-SHIFT LINE EXTENDED FROM NEAR TPA
SSWWD ACROSS GULF TO ABOUT 100 W FMY AND BEYOND. BAND OF TSTMS HAS
DEVELOPED ALONG THAT TROUGH AND NEAR SFC MOIST/WARM AXES THAT EXTEND
NWD FROM YUCATAN STRAIT. COASTAL AIR MASS ALONG AND S OF OUTFLOW
BOUNDARY IS CHARACTERIZED BY SFC DEW POINTS UPPER 60S F AND TEMPS
LOW 70S...NOT QUITE AS WARM ON EITHER COUNT AS OVER CONVECTIVE
GENESIS AREA OFFSHORE BUT STILL POTENTIALLY SUPPORTING SFC-BASED
EFFECTIVE INFLOW PARCELS. SFC THETAE DIMINISHES WITH EWD EXTENT
FROM CURRENT CONVECTIVE AREA TO COAST AND IS MINIMIZED INLAND NEAR
COAST. THIS FACTOR AND WEAK LAPSE RATES ALOFT COMBINE TO YIELD
RELATIVE MIN IN MUCAPE NEAR COAST -- LESS THAN 500 J/KG BASED ON
MODIFIED FCST SOUNDINGS.

THIS PRECONVECTIVE ENVIRONMENT SHOULD CONTINUE THROUGH REMAINDER
OVERNIGHT HOURS...WITH SOME FURTHER LOSS OF INLAND THETAE DUE TO
ADDITIONAL DIABATIC SFC COOLING. SOME ONSHORE FLOW IS POSSIBLE
LATER TODAY -- I.E. AFTER ABOUT 15Z -- HOWEVER UNTIL
THEN...COAST-PARALLEL TO SLGT OFFSHORE COMPONENT SHOULD MAINTAIN
TIGHT THETAE/INSTABILITY GRADIENT INVOF COAST. AS SUCH...CONVECTIVE
POTENTIAL WITH INLAND EXTENT BECOMES MORE CONDITIONAL AND SVR THREAT
VERY LOW...DESPITE FAVORABLE KINEMATIC ENVIRONMENT WITH 40-50 KT
EFFECTIVE SHEAR MAGNITUDES.

..EDWARDS/KERR.. 04/04/2013

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MFL...TBW...

LAT...LON 27468267 27388242 27128207 26508177 25908157 25948173
26198182 26398189 26468198 26398205 26458219 26548222
26838227 27078247 27468267

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