Quantitative Precipitation Forecast
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FOUS30 KWBC 010056
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
855 PM EDT SAT APR 30 2016

...VALID 01Z SUN MAY 01 2016 - 12Z SUN MAY 01 2016...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 SE RAM 40 SE KDLP 15 NE 1B7 20 NNW MOB 20 NNW PNS 45 SSE NPA
30 SE RAM.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW 1A5 25 SSE TRI 10 N UKF 15 SW INT 10 SSW EQY 20 SW HQU
15 ESE ATL 15 NNE 47A 20 NNW 1A5.


...LOWER MS VALLEY...

2100 UTC UPDATE...HAVE REMOVED THE MODERATE RISK AND TRIMMED THE
PREVIOUS SLIGHT RISK AREA...NOW CONFINED TO EASTERN LA...SOUTHERN
MS-AL...AND THE FAR WESTERN FL PANHANDLE BASED ON THE PROGRESSION
AND OVERALL WEAKENING TREND OF THE MCS. LATEST GOES-14 SRSO
LONGWAVE IR LOOPS SHOW A GRADUAL WARMING/LOWERING OF CLOUD
TOPS...WHICH IS CORRESPONDING TO THE LOWERING OF THE 1-3 HR
RAINFALL RATES PER THE LATEST RADAR ESTIMATES. DESPITE THE
WEAKENING TRENDS...GIVEN THE CONTINUED W-E EXPANSE OF MOD-HEAVY
RAIN CORES ALONG WITH THE DEGREE OF DEEP-LAYER INSTABILITY STILL
IN PLAY DOWNWIND (MUCAPES 2000-2500 J/KG)...LOCALIZED RAINFALL
AROUND 2"/HOUR AND 3-4" WITHIN 3 HOURS WILL NONETHELESS LEAD TO
ISOLATED SHORT-TERM RUNOFF ISSUES...PARTICULARLY THROUGH EARLY
EVENING. AS WAS NOTED IN PREVIOUS DISCUSSIONS...THE HIGH-RES CAM
GUIDANCE HAS NOT HANDLED THIS EVENT PARTICULARLY WELL OVERALL.
MUCH OF THE GUIDANCE NOTED A WET BIAS NORTH OF THE MCS...WHILE AT
THE SAME TIME TOO SLOW WITH THE EASTWARD PROGRESSION.

AS THE DECAYING MCS CONTINUES EAST...AWAY FROM THE STRONGEST
SOUTHERLY LOW LEVEL INFLOW...INCREASED LOW-MID LAYER SHEAR WILL
MAINTAIN A PROGRESSIVE EASTWARD COMPONENT...LEADING TO A STEADY
DECLINE IN THE EXCESSIVE RAINFALL POTENTIAL LATER THIS EVENING.


...SOUTHERN APPALACHIANS INTO NORTHEAST GA...

2100 UTC UPDATE...STRENGTHENING UPPER LEVEL DIFFLUENCE AND
DEEP-LAYER WAA/ASCENT ALONG AND NORTH OF THE SURFACE WARM
FRONT...ALONG WITH A POOL OF MODEST INSTABILITY ALONG AND NORTH OF
THE BOUNDARY (MUCAPES 1000-2000 J/KG)...IS ALLOWING FOR AN
EXPANDING AREA OF CONVECTION ACROSS NORTHEAST GA...NORTHWEST SC...
EASTERN TN...AND WESTERN NC. FFG VALUES ARE HIGH INITIALLY (3-4"
WITHIN 3 HOURS)...HOWEVER THE EXPECTATION FOR RE-FIRING AND (THUS)
SOME TRAINING OF CONVECTION NORTH OF THE WARM FRONT...WITH
CONTINUED SUFFICIENT INSTABILITY WITHIN THE GENESIS REGION...ALONG
WITH THE LIKELIHOOD OF SOME OROGRAPHIC CONTRIBUTION AND
POTENTIALLY A FAIRLY RAPID DROP IN THE FFG FOLLOWING THE INITIAL
ROUNDS OF CONVECTION BASED ON THE TERRAIN (CLIMATOLOGY).
AREAL-AVERAGE TOTALS ARE EXPECTED TO MAX OUT BETWEEN 1-1.5" PER
THE LATEST WPCQPF...HOWEVER AS NOTED WITH SOME OF THE HIGH-RES CAM
GUIDANCE (INCLUDED THE LATEST HRRR AND 18Z NAM CONEST)...ISOLATED
TOTALS OF 3-6" WILL BE POSSIBLE THROUGH MIDNIGHT (~04Z) WHILE THE
INSTABILITY IS EXPECTED TO REMAIN SUFFICIENT.

HURLEY
$$





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