MESOSCALE PRECIPITATION DISCUSSION 0070
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
829 PM EDT SAT MAY 09 2015
 
AREAS AFFECTED......NORTHEAST TX/EASTERN OK/AR... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 100029Z - 100429Z
 
SUMMARY...

DISCUSSION...CONVECTION WILL CONTINUE TO TRACK OVER AREAS OF
NORTHEAST TX...EASTERN OK AND PORTIONS OF AR THAT RECEIVED HEAVY
RAIN EARLIER SATURDAY. THE ADDITIONAL RAINFALL IS EXPECTED TO
PRODUCE FLASH FLOODING.

NEW CONVECTION CONTINUES TO DEVELOP OVER PORTIONS OF NORTHEAST TX
AND SOUTHEAST OK IN A RIBBON OF MLCAPES BETWEEN 2500 AND 3500
J/KG. AS THE CONVECTION TRACKS NORTHEAST INTO EASTERN OK AND
WESTERN AR...THE INSTABILITY IS NOT NEARLY AS RICH (AS THE AIRMASS
HAS BEEN COMPROMISED BY EARLIER CONVECTION)...BUT PRECIPITABLE
WATER VALUES TOP OUT NEAR 1.75 INCHES ON THE NOSE OF A 30 TO 40
KNOT LOW LEVEL SOUTHERLY FLOW. RADAR ESTIMATES AND MESONET
OBSERVATIONS INDICATE THAT THE NEWLY FORMED CONVECTION IS
PRODUCING RAINFALL RATES NEAR 2 INCHES AN HOUR OVER NORTHEAST
TX...AND THIS ACTIVITY WILL CONTINUE TO MOVE OVER EASTERN OK AND
MUCH OF AR.

MUCH OF THE AVAILABLE HIGH RESOLUTION GUIDANCE (INCLUDING THE
LATEST HRR...RAP AND WRF-ARW) SUGGEST THAT THE CONVECTION WILL
FOLLOW THE BEST INSTABILITY ACROSS NORTHEAST TX...SOUTHEAST OK
INTO NORTHERN AND CENTRAL AR. THE 12Z WRF-ARW IS THE MOST ROBUST
WITH QPF VALUES...SUGGESTING THE POTENTIAL FOR AN ADDITIONAL 3 TO
5 INCHES OF RAINFALL... ESPECIALLY IN THE VICINITY OF CELL MERGERS.
THE LATEST HRRR IS MORE CONSERVATIVE... SHOWING ADDITIONAL
RAINFALL VALUES TOPPING OUT NEAR 3 INCHES. 

ONE AND THREE HOUR FLASH FLOOD GUIDANCE VALUES ARE AS LOW AS UNDER
1 INCH... ESPECIALLY OVER NORTHEAST TX AND SOUTHEAST OK. GIVEN THE
LOW FFG VALUES AND HIGH RAINFALL RATES...FLASH FLOODING IS
CONSIDERED LIKELY.


HAYES

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

ATTN...RFC...ABRFC...LMRFC...WGRFC...

LAT...LON   36619252 36439134 35619093 33959159 33339343 
            32839661 32709832 32979935 33669993 34159974 
            34159974 35349804 36239606 36259603 36439477