SWOMCD
SPC MCD 181720
FLZ000-181945-
MESOSCALE DISCUSSION 0322
NWS STORM PREDICTION CENTER NORMAN OK
1220 PM CDT SUN APR 18 2010
AREAS AFFECTED...PORTIONS S FL AND KEYS.
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY
VALID 181720Z - 181945Z
TSTMS SHOULD DEVELOP AND/OR MOVE INLAND THROUGH REMAINDER
AFTERNOON...WITH POTENTIAL FOR DOWNDRAFT GUSTS APCHG SVR LIMITS.
SHORT-LIVED SUPERCELL EVOLUTION ALSO IS POSSIBLE...ESPECIALLY INVOF
WARM FRONT OR SEA BREEZES WHERE LOW-LEVEL VORTICITY MAY BE
ENHANCED...IN ENVIRONMENT OF LOW LCL. THEREFORE...MRGL/CONDITIONAL
TORNADO POTENTIAL ALSO EXISTS.
MID-UPPER TROUGH OVER EXTREME E-CENTRAL GULF SHOULD CONTINUE TO
EJECT NEWD TOWARD W-CENTRAL/SW FL COAST. VIS IMAGERY AND SFC
MESOANALYSIS SHOWS TRANSITION FROM OVC TO BKN CLOUD
COVER...GENERALLY CORRESPONDING TO SFC WARM FRONT...MOVING NWD
THROUGH CORRIDOR FROM NEAR MARCO ESEWD ACROSS SRN MIAMI-DADE COUNTY.
BOUNDARY SHOULD LIFT NWD ACROSS I-75 THROUGH MIDAFTERNOON...BENEATH
DRY SLOT ALOFT THAT PRECEDES MID-UPPER TROUGH. SFC LOW SHOULD MOVE
SLOWLY EWD TOWARD WATERS BETWEEN MARCO-EYW. DESPITE SFC FLOW NOT
BEING AS BACKED AS INVOF WARM FRONT...INCREASING WINDS ALOFT WITH
SLY EXTENT IN WARM SECTOR WILL HELP TO MAINTAIN FAVORABLE DEEP-LAYER
SHEAR OVER MOST OF S FL AND KEYS. EXPECT ENHANCED MID-UPPER LEVEL
FLOW AHEAD OF THIS TROUGH -- E.G. 30-40 KT AT 500 MB -- TO
CONTRIBUTE TO FAVORABLE EFFECTIVE SHEAR MAGNITUDES 40-50 KT.
AS WARM FRONT MOVES NWD...INCREASING INLAND AREA WILL HEAT TO ITS
S...CONTRIBUTING TO INCREASING BUOYANCY AND NEGLIGIBLE MLCINH.
MODIFIED RAOBS AND RUC FCST SOUNDINGS SUGGEST SUCH DESTABILIZATION
AND SFC DEW POINTS NEAR 70 F WILL OFFSET WEAK LAPSE RATES ALOFT
ENOUGH TO YIELD 500-1000 J/KG PRE-STORM MLCAPE. LIMITING FACTORS
INCLUDE LACK OF GREATER CAPE...WEAKNESSES IN 0-3 KM HODOGRAPHS...AND
RATHER DIFFUSE FOCI FOR ASCENT S OF WARM FRONT. MESOBETA SCALE TO
STORM-SCALE BOUNDARY/CELL INTERACTIONS MAY BE MOST CRITICAL FOR
LOCALIZED SVR POTENTIAL.
..EDWARDS.. 04/18/2010
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...MFL...KEY...TBW...
LAT...LON 25538016 25238030 24958054 24698099 24628132 24598149
24558164 24528180 24518198 24578222 24608210 24598173
24708168 24768149 24808128 24738113 24838086 24928087
25028102 25188115 25238121 25338113 25328105 25398112
25508121 25808139 25918163 25818168 26078180 26328184
26478192 26498083 26388003 25538016
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