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000
FOUS30 KWBC 191028
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
628 AM EDT SUN MAY 19 2013

...VALID 12Z SUN MAY 19 2013 - 12Z MON MAY 20 2013...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
40 NW P59 35 N LNL 25 WNW MDZ 20 ENE MCW 15 W SLB 40 W YKN
45 E IEN 25 ESE SIB 25 W IDV 45 E LVM 25 NE 3HT 40 ESE LWT
45 SSE JDN 10 NE SDY 10 N CXMD 45 SSE CYHD 25 NNW CYQT 40 NW P59.


...NRN HIGH PLAINS EAST INTO THE UPPER MISSISSIPPI VALLEY...

THE MUCH DISCUSSED WRN U.S. UPPER TROUGH WILL TAKE ON A MORE
NEGATIVE TILT WHILE GRADUALLY MOVING INTO THE PLAINS TODAY. THE
ANTICIPATED BROAD AREA OF STRONG UPPER LEVEL DIFFLUENCE AND AGEOS
DIVERGENCE WILL ENSUE WITH THE AMPLIFICATION AND DEVELOPING UPPER
LEVEL "S" PATTERN...AIDED BY THE  COUPLING JET DYNAMICS VIA THE
LEFT EXIT/RIGHT ENTRANCE REGION OF THE SRN/NRN BRANCHES
RESPECTIVELY.
THIS WILL GENERATE A FAIRLY SIZABLE AREA OF ASCENT...COINCIDING
WITH PROLONGED MOIST INFLOW (~30 TO 40 KTS AT 850 MB WITH PW`S OF
1 TO 1.5" OR 2-2.5 STD DEVIATIONS ABOVE THE NORM.

EXPANDED THE EXCESSIVE RAINFALL RISK AREA FARTHER W INTO THE HIGH
PLAINS OF SERN MT/NW CO GIVEN THE ANTICIPATED BACK-BUILDING LLVL
THETA-E AND HIGH PW AXIS...ALONG WITH THE AFOREMENTIONED ROBUST
AREA OF ENHANCED UPPER AGEOS DIVERGENCE/UPWARD ASCENT.  3 AND 6 HR
FFG VALUES ARE LOWER IN THESE AREAS AS WELL.  THE
MODELS...PARTICULARLY THE HIGH-RES RUNS...CONTINUE TO SHOW SPATIAL
AND TIMING DIFFERENCES WITH THE AXES OF HEAVIEST RAIN (AS EXPECTED
GIVEN THE CONVECTIVE NATURE...EVEN WITH FVRBL...BROAD UPPER
DIVERGENCE).  AS A RESULT...FOR NOW THE EXCESSIVE RAINFALL RISK
REMAINS SLIGHT...THOUGH IT SHOULD BE NOTED THAT THE
SREF/GEFS/ECENS PROBABILITIES OF AREAL-AVERAGE QPF > 2-3" IN 24
HOURS HAS INCREASED AND EXPANDED TOWARD MT/WY WITH THE MOST RECENT
RUNS.


...CENTRAL PLAINS...

LOCALLY EXCESSIVE RAINFALL WILL BE POSSIBLE ACROSS ERN PTNS OF THE
CENTRAL PLAINS SUN NIGHT INTO EARLY MON MORNING...AS THE
AFOREMENTIONED AMPLIFYING TROUGH INDUCES A 40-50 KT LLJ COINCIDING
WITH AMPLE MOISTURE TRANSPORT (PW`S NEAR 1.5").  AS WITH AREAS TO
THE N...STRONG UPPER LEVEL DYNAMICS (UL DIFFLUENCE/AGEOS
DIVERGENCE) WILL AID IN THE DEVELOPMENT OF ORGANIZED MULTICELLULAR
CONVECTION.  CAPES WILL BE HIGHER IN THIS AREA HWVR...POTENTIALLY
LEADING TO A MORE SEVERE WX THREAT THAN ONE FOR ORGANIZED FLASH
FLOODING (MBE OR CORFIDI VECTORS ARE IN FACT RATHER PROGRESSIVE
AFTER 00Z).  STILL...GIVEN THE FVRBL DYNAMICAL AND THERMODYNAMICAL
SETUP...CANNOT RULE OUT SCATTERED AREAS OF FLASH FLOODING OVER
THIS REGION.


...SOUTHEAST...

ADDITIONAL WAVES OF CONVECTION ALONG A STATIONARY LLVL BNDRY (AND
WITHIN A COMPACT DIFFLUENT FLOW PATTERN ALOFT) WILL AGAIN INTERACT
WITH PW`S AROUND 1.5"  TO GENERATE ADDITIONAL AREAS OF POTENTIALLY
EXCESSIVE RAINFALL.  THE HIGHEST THREAT FOR FLASH FLOODING WILL BE
OVER THE ELEVATED AREAS IN NE GEORGIA AND NW SC...WHERE THE FFG
WILL BE LOWER IN COMPARISON TO SURROUNDING AREAS.

HURLEY
$$