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000
FOUS30 KWBC 201857
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT MON MAY 20 2013

...VALID 18Z MON MAY 20 2013 - 00Z WED MAY 22 2013...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
20 NNW GMJ 30 NE JLN 40 N SGF 30 WSW AIZ AIZ 20 E AIZ
10 NNW TBN 10 SSW TBN 30 SSW TBN 40 WNW UNO 35 N BPK 15 NW BPK
15 W FLP 25 SW FLP 25 SSW FLP 25 S FLP 30 WNW BVX 20 N BVX
25 W ARG 10 SW ARG 10 E M19 10 SE SRC 10 ESE LRF 25 SSW MWT
25 SW DEQ 10 WSW PRX 25 W PRX 10 ENE DUA 20 WSW AQR 10 NE ADM
10 SSW PVJ 10 NW PVJ 15 E OUN 10 N SNL RVS 20 NNW GMJ.



EASTERN OK---SOUTHWEST MO INTO NORTHWEST AR

THERE IS A VERY GOOD CHANCE OF HEAVY RAINFALL THIS PERIOD IN THE
VICINITY OF THE THE SURFACE FRONTAL BOUNDARY CURRENTLY STRETCHING
FROM THE CENTRAL TO SOUTHERN PLAINS WHICH WILL BECOME VERY SLOW
MOVING FROM THE SOUTHERN PLAINS INTO THE MID MS VALLEY REGION.
STRENGTHENING SOUTHERLY TO SOUTHWESTERLY LOW LEVEL INFLOW INTO AND
AHEAD OF THIS BOUNDARY WILL RAISE PW VALUES TO 1.5-2 STANDARD
DEVIATIONS ABOVE THE MEAN.  THIS---STRONG FRONTAL CONVERGENCE AND
VERY FAVORABLE UPPER DIFFLUENCE IN THE COUPLED JET EXIT/ENTRANCE
REGION OVR THE SOUTHERN PLAINS WILL SUPPORT VERY ACTIVE CONVECTION
BEGINNING LATE AFTERNOON/EVENING AND CONTINUING THROUGH THE
REMAINDER OF THE FORECAST PERIOD.  THERE MAY BE A BREAK IN
ACTIVITY BETWEEN CONVECTION OVERNIGHT INTO TUE MORNING AND THEN A
SECOND ROUND LATER TUESDAY AFTERNOON---BUT OVERALL A VERY ACTIVE
PRECIPITATION PERIOD LIKELY ACROSS PORTIONS OF THE SOUTHERN PLAINS
INTO THE MID MS VALLEY REGION.  THERE MAY BE A PERIOD OF TRAINING
OR BACK BUILDING OF CELLS IN THE SOUTHWESTERLY FLOW ALONG THIS
FRONT LATE TONIGHT INTO EARLY TUESDAY.  IN AREAS OF TRAINING/BACK
BUILDING---ISOLATED 2-3"+ PRECIPITATION AMOUNTS POSSIBLE IN A FEW
HOURS.  WHILE THERE ARE MORE NUMEROUS DIFFERENCES IN QPF DETAILS
ON THE SHORTER FORECAST TIME SCALE AMONG THE LATEST MODELS---THERE
IS BETTER AGREEMENT OVERALL FOR THIS FORECAST PERIOD FOR HEAVY
RAINFALL POTENTIAL FROM NORTHEASTERN TX---ACROSS EASTERN TO
SOUTHEAST OK--CENTRAL TO NORTHERN AR AND INTO CENTRAL TO SOUTHERN
MO.

NORTHERN PLAINS/UPPER MS VALLEY

THERE IS GOOD AGREEMENT IN THE LATEST MODEL GUIDANCE WITH THE VERY
SLOW EASTWARD PUSH OF THE STRONG CLOSED LOW INITIALLY OVER THE
EASTERN PORTION OF THE NORTHERN PLAINS.  A PERSISTENT COMMA
HEAD/DEFORMATION PRECIPITATION BAND WILL AFFECT THE NORTHERN
PLAINS INTO THE FAR NORTHERN UPPER MS VALLEY WITH A DURATION
MODERATE TO ISOLATED HEAVY PRECIPITATION EVENT.  GIVEN THE
EXPECTED LONG DURATION OF MODERATE PRECIPITATION AMOUNTS---DO NOT
BELIEVE THERE WILL BE A SIGNIFICANT RISK OF RUNOFF ISSUES FROM 6
HOURLY AMOUNTS OF .25-.50+ AND ISOLATED TOTALS OF 1-1.5"+ FOR THE
FORECAST PERIOD.

ORAVEC
$$