Flash Flood Guidance
Issued by NWS

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000
AWUS01 KWNH 231517
FFGMPD
FLZ000-GAZ000-232016-

MESOSCALE PRECIPITATION DISCUSSION 0005
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1016 AM EST FRI JAN 23 2015

AREAS AFFECTED...NORTHEAST FL & SOUTHERN GA

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

VALID 231516Z - 232016Z

SUMMARY...A CONVECTIVE BAND IS ABOUT TO BECOME QUASI-STATIONARY
ACROSS NORTHERN FL, INCREASING THE RISK OF CELL TRAINING OVER AN
AREA OF SATURATING/CLAY SOILS.  FLASH FLOODING IS POSSIBLE.

DISCUSSION...A LENGTHENING/SOLIDIFYING BAND OF THUNDERSTORMS HAS
DEVELOPED AHEAD OF A WAVY COLD FRONT, EXTENDING FROM THE LOOP
CURRENT IN THE CENTRAL GULF OF MEXICO NORTHEAST TOWARDS THE
EASTERN FL PANHANDLE, WHICH SHOWS COOLING CLOUD TOPS ON SATELLITE
IMAGERY.  SATELLITE AND RADAR IMAGERY SUGGEST THE FORWARD
PROGRESSION OF THE LINE IS SLOWING AS A SHORTWAVE ESCAPES TO THE
NORTH THROUGH GA.  INFLOW AT 850 HPA IS SOUTHWEST AT 50 KTS PER
THE TLH VAD WIND PROFILE, WHICH SLIGHTLY EXCEEDS THE 850-400 HPA
MEAN WINDS, ALLOWING FOR PRECIPITATION EFFICIENCY.  PRECIPITABLE
WATER VALUES (DERVIED BY SATELLITE) ARE CLOSE TO 1.8" IN THIS
AREA, NEAR RECORD VALUES FOR LATE JANUARY.  CAPE VALUES EXCEEDING
500 J/KG LURK JUST OFFSHORE THE FL PANHANDLE.

RECENT RAP RUNS SUGGEST THAT A WEAK POLAR WARM FRONT SHOULD CROSS
FL TODAY, TURNING LOW-LEVEL WINDS TO MORE SOUTHWESTERLY, CREATING
A DEEP UNIDIRECTIONAL WIND PATTERN WITH HEIGHT.  BOTH THE TLH AND
JAX SOUNDINGS ARE MOIST, WITH FREEZING LEVELS MORE THAN 11,000
FEET ABOVE GROUND LEVEL -- WARM RAIN PROCESSES SHOULD BE AT PLAY.
RECENT HRRR, RAP, 06Z REGIONAL CANADIAN MODEL, AND 12Z NAM CONEST
GUIDANCE APPEAR TO HAVE THE BEST HANDLE ON THE CONVECTIVE
SITUATION, WITH THE LAST FEW HRRR RUNS INDICATING LOCAL AMOUNTS OF
4-7" POSSIBLE THROUGH 21Z, WHICH WOULD EXCEED FLASH FLOOD GUIDANCE
VALUES.  THE 06Z GFS AND RECENT RAP RUNS INDICATE FORWARD
PROPAGATION TO THE CONVECTION ACROSS NORTHERN FL SHOULD CONTINUE
TO SLOW OVER THE NEXT FEW HOURS, INCREASING THE RISK OF CELL
TRAINING.  AVAILABLE MOISTURE VALUES SUGGEST HOURLY RAIN RATES
NEAR 2" ARE POSSIBLE, WHICH RADAR INDICATES IS BEING EXCEEDED
NORTHWEST OF APALACHICOLA.  WITH SATURATING AND CLAY SOILS ACROSS
THIS AREA, FLASH FLOODING IS CONSIDERED POSSIBLE OVER THE NEXT
SEVERAL HOURS.

ROTH

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

ATTN...WFO...JAX...TAE...TBW...

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

LAT...LON   31468238 31258173 30708160 29858253 29418317
            29468338 29678352 29858374 30008410 29938429
            29648467 29558501 29488571 29648563 29958506
            30538436 30938378 31348295


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