266
AWUS01 KWNH 182113
FFGMPD
FLZ000-190230-
MESOSCALE PRECIPITATION DISCUSSION 0111
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
512 PM EDT SUN APR 18 2021
AREAS AFFECTED...NORTHERN FLORIDA PENINSULA...
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 182115Z - 190230Z
SUMMARY...TRAINING CELLS CAPABLE OF 2"+/HR RATES AND SATURATED
GROUNDS SUPPORT POSSIBLE RAPID INUNDATION/FLASH FLOODING CONCERNS
THROUGH LATE EVENING HOURS.
DISCUSSION...GOES-E WV SUITE DEPICTS A SOLID SHORTWAVE
SOUTH-SOUTHEAST OF THE MOUTH OF THE MISSISSIPPI RIVER ADVANCING
EASTWARD WITH BROAD UPPER LEVEL DIVERGENCE DOWNSTREAM ACROSS THE
NORTHEASTERN GULF OF MEXICO. AS SUCH, A SURFACE INFLECTION IS
ENHANCING ALONG AN SW-NE ORIENTED BOUNDARY AND ENHANCING SOUTHERLY
FLOW ACROSS THE WEST COAST THE PENINSULA WITH 10-15KT FLOW
STRENGTHENING TO 20-25KTS FROM SURFACE TO 850MB AS THE SHORTWAVE
APPROACHES. THE FRONTAL ZONE IS DRAPED ACROSS THE PENINSULA FROM
BKV TO SOUTH OF MCO, NORTH OF VRB ANCHORED BY OUTFLOW FROM EARLIER
CONVECTIVE OUTFLOW.
WITHIN THE WARM SECTOR, TDS ARE OVER 70F THOUGH 850-7H LPW
SUGGESTS WESTERN ATLANTIC SOURCE OF DRIER AIR...SO INSTABILITY IS
SIZABLE WITH MLCAPES OVER 2000 J/KG, SUGGESTING SOME DRY AIR
ENTRAINMENT MAY RESULT CLOSER/SOUTH OF THE FRONTAL BOUNDARY, BUT
STILL LOW LEVEL INFLOW WOULD BE VERY MOIST, SO SURFACE BASED CELLS
WILL HAVE AMPLE ENTRAINMENT TO PRODUCE SOME MOISTURE FLUX
CONVERGENCE TO SLOWLY SATURATE PROFILES FOR INCREASED RAINFALL
EFFICIENCY WELL AFTER MATURITY. LPW ALSO DENOTES A MORE DEEPLY
SATURATED ENVIRONMENT ACROSS THE PANHANDLE AND FAR NORTHERN
FLORIDA WITH DEEPEST MOISTURE OF 1.75 TO 2" ALONG THE FRONTAL
ZONE/INVERTED SURFACE TROF AXIS ALONG/AHEAD OF SHORTWAVE
HEIGHT-FALLS. DEEP UNIDIRECTIONAL FLOW NORTH OF THE SURFACE
BOUNDARY ALONG THE 850MB TROF AXIS WOULD HAVE GREATER MOISTURE
AVAILABILITY THOUGH INSTABILITY WOULD HAVE SIZABLE REDUCTION
GIVEN THE NARROWER PROFILES WITH AT MOST MUCAPE OF 1000-1250 J/KG.
AS SUCH, A NARROW AXIS FROM LEVY/CITRUS COUNTY TO FLAGLER/N
VOLUSIA COUNTY WOULD BE THE INTERSECTION OF BEST INSTABILITY AND
MOISTURE. STRONG CONVECTIVE CORES ALONG THIS AXIS WILL HAVE THE
CAPABILITY OF PRODUCING QUICK BURST (1.25"/15MINS PER HRRR) RATES,
PARTICULARLY AS BEST FORCING AND MATURITY OF CONVECTIVE
DEVELOPMENT OCCURS NEARER TO 23-00Z ALONG/NEAR NW FLORIDA COAST.
CELLS SHOULD BE QUICK MOVING BUT HAVE A TRAINING ORIENTATION
RESULTING IN RAINFALL TOTALS OF 2-3" ARE POSSIBLE BUT COULD EVEN
REACH 4" IN VERY ISOLATED LOCATIONS THROUGH 03Z. IF THE TRAINING
AXIS REMAINS FAIRLY STABLE, WHICH CURRENT TRENDS SUGGEST GIVEN
AMPLITUDE OF THE WAVE APPROACHING, THE AXIS OF HEAVIEST RAINFALL
MAY TRACK THROUGH AREAS SATURATED LATE LAST EVENING WITH 2-3" FROM
MARION TO FLAGLER COUNTY,RESULTING IN AREA OF GREATEST RISK FOR
RAPID INUNDATION/FLASH FLOODING.
SOME DRY AIR ENTRAINMENT COULD RESULT IN COLD POOLS THAT COULD SAG
THE AXIS SOUTH, WHERE GROUND CONDITIONS ARE A BIT BETTER BUT AHPS
WEEKLY ANOMALIES ARE WELL OVER 300% OF NORMAL. NASA SPORT SOIL
SATURATION THROUGH 0-40 CM ARE FULLY SATURATED ACROSS THE
PANHANDLE INTO NORTHERN FLORIDA (OVER 98%) WHILE BELOW 70% ACROSS
THE I-4 CORRIDOR, THOUGH HAS GREATER URBAN SETTINGS AND MORE
HYDROPHOBIC HIGH-RUNOFF CAPABILITY. AS SUCH, HAVE ENCOMPASSES
THESE AREAS INTO THE AREA OF CONCERN.
GALLINA
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...JAX...MLB...TAE...TBW...
ATTN...RFC...SERFC...NWC...
LAT...LON 30108184 30018122 29288088 28168041 28028106
28158203 28328281 28598287 28888288 29438334
29868352 30058258
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