MESOSCALE PRECIPITATION DISCUSSION 0056
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1219 AM EDT TUE MAY 21 2013
 
AREAS AFFECTED...SOUTHERN AND EASTERN OK...NORTHWEST AR...AND
SOUTHWEST MO 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 210419Z - 210819Z
 
SUMMARY...LOWERING FLASH FLOOD GUIDANCE VALUES -- FFGS -- AND
NEWLY DEVELOPING CONVECTION JUST AHEAD OF A COLD FRONT ACROSS
NORTHEAST OK AND NORTH OF AN OUTFLOW BOUNDARY ACROSS SOUTHERN OK
COULD LEAD TO FLASH FLOODING OVERNIGHT.

DISCUSSION...BOTH AN OUTFLOW BOUNDARY LOCATED ACROSS NORTHEAST TX
AND A SYNOPTIC-SCALE COLD FRONT SLICING ACROSS CENTRAL OK HAVE
SHOWN A RECENT UPTICK IN PRECIPITATION COVERAGE AND INTENSITY IN
THEIR VICINITIES.  WHILE MOST OF THE MESOSCALE GUIDANCE INDICATED
THE INCREASE ACROSS SOUTHERN OKLAHOMA TO BEGIN BY 09Z, THE NEW
LINE IN NORTHEAST OKLAHOMA WAS HANDLED POORLY.  LIKE LAST NIGHT,
850 HPA INFLOW SLOWLY SHIFTS WESTWARD WITH TIME OVERNIGHT AS A
MID- TO UPPER-LEVEL SHORTWAVE APPROACHES THE REGION FROM NEW
MEXICO.  THIS COULD ALLOW FOR ADDITIONAL BACK BUILDING OF
THUNDERSTORMS WESTWARD ACROSS SOUTHERN OK.  UP THE NORTH, NEAR THE
FRONTAL ZONE, LITTLE MOVEMENT OF THE BOUNDARY IS EXPECTED
OVERNIGHT, WHICH COULD LEAD TO CELL TRAINING NEAR AND AHEAD OF THE
BOUNDARY.  WHILE 850 HPA INFLOW IS WEAKER THAN LAST NIGHT -- ON
THE ORDER OF 30-35 KNOTS -- FFGS ACROSS THE REGION HAVE LOWERED
DUE TO THE RAINFALL WHICH HAS OCCURRED SINCE SUNDAY EVENING. 
REGIONALLY, FFGS ARE DOWN WITH 2.5 INCHES/3 HOURS WHILE SOUTHWEST
MISSOURI SHOWS VALUES UNDER 2 INCHES/3 HOURS.  PRECIPITABLE WATER
VALUES -- PWS -- ARE IN THE 1.50-1.75 INCH RANGE, WHICH COULD LEAD
TO LOCAL RAINFALL AMOUNTS OF 3-5 INCHES WHERE CELLS TRAIN. 
PROPAGATION/CORFIDI VECTORS ARE ALIGNED WSW-ENE, WHICH COULD ALLOW
THE OK THUNDERSTORM ACTIVITY TO MOVE INTO NORTHWEST AR, FAR
SOUTHEAST KS, AND SOUTHWEST MO.  THERE IS A DECENT CHANCE THAT THE
THUNDERSTORM ACTIVITY COULD PERSIST PAST DAWN.  CONFIDENCE IN
REGIONAL FLASH FLOODING IS MODEST, AND CURRENT CONVECTIVE
ORGANIZATION IS STILL LACKING, WHICH LEAD TO THE POSSIBLE WORDING
OVER LIKELY WORDING.

ROTH


ATTN...WFO...LZK...SGF...SHV...TSA...FWD...OUN...

LAT...LON   36169664 37199467 37509354 37129275 35599284 34369386
            33879549 33939799 34569943 36169664