000
FOUS30 KWBC 181002
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
601 AM EDT SAT MAY 18 2013

...VALID 12Z SAT MAY 18 2013 - 12Z SUN MAY 19 2013...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NW CWCH 30 NNW ELO 10 NNW PWC 10 NW AQP 40 W YKN 25 N VTN
40 SW K46D 25 W CWSU 30 SSW CYHD 20 NW CWCH.


...NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY...

CURRENT STLT IR/WV IMAGERY AND OBSERVATIONAL DATA SHOW THE ONGOING
MCS ACROSS THE NRN PLAINS BECOMING A BIT LESS ORGANIZED (WITH
WARMING CLOUD TOPS) AS THE ELEVATED CONVECTION STRAYS FARTHER AWAY
FROM BEST DYNAMICAL SUPPORT (RIGHT ENTRANCE REGION UPPER LEVEL
DIVERGENCE). MOREOVER...THE MB OR CORFIDI VECTORS ARE INDICATIVE
OF A FAIRLY PROGRESSIVE SYSTEM TO THE ENE.

THE MAIN CONCERN OVER THE THREAT REGION HOWEVER IS FOR LATER THIS
AFTERNOON AND ESPECIALLY TONIGHT AS THE TROUGH CONTINUES TO
AMPLIFY (BECOME MORE NEGATIVELY TILTED)...AND THEREBY GENERATING A
FAIRLY SIZABLE AREA OF UPPER LEVEL DIFFLUENCE AND AGEOS
DIVERGENCE...COINCIDING WITH A DEVELOPING LLJ ~30 KTS AND PW`S
~1.25" (WHICH IS ABOUT 2 STD DEVIATIONS ABOVE THE NORM). ELEVATED
LLVL MSTR FLUX CONVERGENCE (925-850 MB) IS EXPECTED TO BE ON THE
ORDER OF 2.5-3.0 STD DEVIATIONS ABOVE NORMAL WITH THE ANTICIPATED
MCS TONIGHT PER BOTH THE SREF AND GEFS STANDARDIZED ANOMALIES.
MODEL QPF GUIDANCE STILL VARYING QUITE A BIT WITH RESPECT TO THE
EXACT PLACEMENT...AS WITH THE UPPER BOUND IN TERMS OF AMOUNTS.
WPC OPTED FOR AN ENSEMBLE APPROACH WITH THE MAX AMOUNTS...
INCORPORATING THE GLOBAL RUNS...HIGH RES WINDOWS...AND OTHER HIGH
PRES GUIDANCE SUCH AS THE SPC AND NSSL WRFS AND SSEO MEAN. THIS
APPROACH...WHILE ALSO INCORPORATING THE SREF/GEFS/ECENS
PROBABILITIES OF AREAL-AVERAGE RAINFALL EXCEEDING 2
INCHES...POINTS TO AN ELEVATED RISK FROM ERN ND/SD INTO NW
MN...MAINLY FOR SAT NIGHT/EARLY SUN MORNING. THE BULK OF THIS
REGION WILL SEE A REDUCTION IN THE FFG VALUES PER THE MCS ACTIVITY
LATE FRI NIGHT AND EARLY SATURDAY MORNING. FOR NOW...THE EXCESSIVE
RAINFALL RISK IS A SLIGHT ONE GIVEN THE AREAL UNCERTAINTY OF WHERE
THE HEAVIEST RAIN IS EXPECTED SATURDAY NIGHT.


...NORTHERN MISSISSIPPI/ALABAMA/GEORGIA...

A W-E AXIS OF FRBL LLVL MSTR TRANSPORT/FLUX CONVERGENCE ALONG A
QUASI-STATIONARY FRONTAL BNDRY WITH PW`S NEAR 1.75" IS ALLOWING
FOR TRAINING CONVECTION ACROSS NORTHERN PTNS OF MS/AL/GA EARLY
THIS MORNING. FOR FURTHER DETAILS...PLEASE REFER TO THE MESOSCALE
PRECIPITATION DISCUSSION OR FFGMPD #42...WHICH REMAINS IN EFFECT
UNTIL 1230Z.

HURLEY
$$