Flash Flood Guidance
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000
AWUS01 KWNH 171410
FFGMPD
FLZ000-172005-

MESOSCALE PRECIPITATION DISCUSSION 0889
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1009 AM EDT TUE OCT 17 2017

AREAS AFFECTED...E-CNTRL TO NERN FL PENINSULA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 171408Z - 172005Z

SUMMARY...NEARLY STATIONARY AREAS OF HEAVY RAINFALL WITH RATES OF
2-3 IN/HR COULD POSE FLASH FLOODING ON A LOCALIZED BASIS ACROSS
THE E-CNTRL TO NERN FL PENINSULA INTO THE EARLY AFTERNOON. 6 HOUR
RAINFALL TOTALS OF 3-5 INCHES WILL BE POSSIBLE THROUGH 20Z.

DISCUSSION...14Z SURFACE OBSERVATIONS PLACED A COLD FRONT ACROSS
THE CNTRL FL PENINSULA...PERPENDICULAR TO THE COAST...CROSSING
INTO SRN BREVARD COUNTY. PRECIPITABLE WATER VALUES ALONG THE
E-CNTRL COAST OF FL ARE ESTIMATED TO BE 1.75 TO 2 INCHES PER THE
12Z TBW SOUNDING MATCHING NEARBY GPS SITES EXTENDING TO THE ERN
PENINSULA WITH LOWER PWAT VALUES TO THE NORTH AND SOUTH. WATER
VAPOR IMAGERY SHOWED A POSITIVELY TILTED UPPER TROUGH AXIS
CROSSING THE E-CNTRL GULF COAST WITH THE TAIL END OF AN UPPER
LEVEL JET MAX CROSSING THE SOUTHEAST COAST WITH GOES HD WINDS
ESTIMATING 80-100 KT NEAR 250 MB OVER THE GA/SC. WHILE THE
GRADIENT IN WIND IS NOT PARTICULARLY STRONG...SOME RIGHT ENTRANCE
REGION UPPER LEVEL DIVERGENCE COULD BE PRESENT AS THE JET AXIS
ADVANCES EAST AHEAD OF THE UPPER TROUGH WHICH MAY HELP TO ENHANCE
LIFT AND CONVECTIVE DEVELOPMENT INTO THE EARLY AFTERNOON.

SHORT TERM FORECASTS OF 850 MB WINDS FROM THE HRRR/RAP INDICATE
700 MB WINDS BECOMING NELY AT 10-20 KT BETWEEN DAYTONA BEACH AND
CAPE CANAVERAL AS THE 700 MB FRONT PASSES BETWEEN 15-18Z. A NARROW
CORRIDOR...~40 MI WIDE...OF 25-30 KT ENELY FLOW IS FORECAST TO
ENTER VOLUSIA COUNTY BEGINNING NEAR 15Z WHICH WOULD HELP TO
SUPPORT TRAINING RAINFALL GIVEN EXCEEDANCE OF MEAN 0-6 KM WINDS OF
NELY AT 10-15 KT BY 18Z. ONE CAVEAT TO THE FORECAST IS THE FACT
THAT VAD WINDS AT 850 MB AND 700 MB ARE BACKED TOWARD THE NORTH
RELATIVE TO THE MODEL FORECASTS OF WIND WHICH MAY KEEP HEAVIER
RAIN OFFSHORE. STILL...SOME DEGREE OF FRICTIONAL CONVERGENCE IS
EXPECTED TO SET UP HELPING TO SUPPORT DEVELOPMENT OF CONVECTION
LATE THIS MORNING. A FEW LIGHT SHOWERS HAVE BEEN NOTED IN THE
VICINITY OF DAYTONA BEACH BUT A POTENTIAL RAPID INCREASE COULD
DEVELOP OVER THE NEXT COUPLE OF HOURS. MLCAPE IS LIMITED IN THE
POST FRONTAL ENVIRONMENT TO COASTAL LOCATIONS WHICH SHOULD LIMIT
THE WESTWARD PENETRATION OF HEAVIER RAINFALL RATES. A RELATIVELY
NARROW WINDOW...IN BOTH SPACE AND TIME...IS EXPECTED TO SET UP
OVER COASTAL PORTIONS OF THE E-CNTRL TO NERN FL PENINSULA TO
SUPPORT LOCALLY HEAVY RAIN WHICH MAY POSE A FLASH FLOOD THREAT
GIVEN EXPECTED TRAINING OF RATES PEAKING IN THE 2-3 IN/HR RANGE.

OTTO

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...JAX...MLB...

ATTN...RFC...SERFC...

LAT...LON   29698112 29208034 27948037 27938082 28698130
            29418148


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