Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 042115
FFGMPD
FLZ000-ALZ000-050043-

MESOSCALE PRECIPITATION DISCUSSION 0786
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
414 PM EST SUN DEC 04 2016

AREAS AFFECTED...FL PANHANDLE...FAR SE AL

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

VALID 042113Z - 050043Z

SUMMARY...NARROW ZONE OF TRAINING CONVECTION WILL LEAD TO ISOLATED
RAIN TOTALS ABOVE 4 INCHES THROUGH 01Z...FLASH FLOODING POSSIBLE.

DISCUSSION...THE FLASH FLOOD THREAT EVOLVING ACROSS FAR NW FLORIDA
AND FAR SE ALABAMA IS VERY SMALL SCALE...BUT NONETHELESS...THE
INGREDIENTS FOR A SEVERAL HOUR PERIOD OF TRAINING CONVECTION
APPEAR TO BE IN PLACE THROUGH 00Z TO 01Z. FLASH FLOOD GUIDANCE
VALUES ARE DIFFICULT TO ACHIEVE IN THIS REGION FOLLOWING WEEKS OF
DRY WEATHER...BUT AT 21Z DUAL-POL ESTIMATES OF 3-HOUR RAINFALL HAD
BEGUN TO EXCEED 3 INCHES...MAKING 4 TO 5 INCH TOTALS A VERY REAL
POSSIBILITY GIVEN THE PREVAILING WINDS AND PERSISTENT SYNOPTIC
FORCING.

THIS REGION IS MARKED BY LARGELY UNIDIRECTIONAL SOUTHWESTERLY FLOW
ATOP A SHALLOW LAYER OF STRONG WARM ADVECTION. INFLOW IS
SUFFICIENTLY UNSTABLE...WITH AIR RISING TO THE NORTH OF A FRONTAL
BOUNDARY AND BEING RELEASED AT THE TAIL END OF DEEP LAYER ASCENT
ASSOCIATED WITH A NORTHERN STREAM TROUGH. RADAR SHOWED A STRONG
TENDENCY TOWARD WEST TO EAST TRAINING...AND VISIBLE SATELLITE
IMAGERY CONTINUED TO SHOW INCIPIENT UPDRAFTS FORMING UPSTREAM OVER
THE GULF. THE CONVECTION WAS RELATIVELY SHALLOW...BUT OVERSHOOTING
TOPS WERE NOTED AS THE LOW SUN ANGLE BEGAN TO REVEAL THEM...AND
MUCH OF THE CLOUD LAYER WILL REMAIN ABOVE FREEZING...YIELDING AN
EFFICIENT WARM RAIN PROCESS WITHIN AIR CHARACTERIZED BY PW VALUES
NEAR 1.80 INCHES.

HI-RES GUIDANCE IS IN GOOD AGREEMENT...AND WE ESPECIALLY FAVOR THE
ARW AND NMM DEPICTION OF MULTI-INCH RAINFALL IN THE DISCUSSION
AREA THROUGH 01Z. THE GREATEST TOTALS MAY OCCUR NEAR AND NORTH OF
I-10 BEFORE A GRADUAL VEERING OF LOW LEVEL FLOW ALLOWS CONVECTION
TO PUSH SOUTH AND EASTWARD THIS EVENING.

BURKE

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

ATTN...WFO...MOB...TAE...

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

LAT...LON   31328571 31268513 30498537 30318721 30728710




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