MESOSCALE PRECIPITATION DISCUSSION 0148
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
825 AM EDT WED APR 26 2017

AREAS AFFECTED...NORTHEAST TX...EASTERN OK...WESTERN AR

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 261223Z - 261820Z

SUMMARY...AN APPROACHING UPPER SHORTWAVE WILL COMBINE WITH STRONG
MOIST LOW LEVEL SOUTHERLY FLOW TO PRODUCE ADDITIONAL HEAVY
RAINFALL ACROSS EASTERN OK...NORTHEAST TX...AND WESTERN AR. HOURLY
RAIN RATES UP TO 2" AND LOCAL RAINFALL TOTALS OF 3-5" COULD RESULT
IN FLASH FLOODING.

DISCUSSION...THE SQUALL LINE EXTENDING FROM NORTHWEST AR INTO
NORTHEAST TX WILL CONTINUE TO PRODUCE LOCALLY HEAVY RAIN AS IT
PROGRESSES SLOWLY EASTWARD DURING THE NEXT SEVERAL HOURS. LOW
LEVEL SOUTHERLY FLOW OF 50-65 KT OVER NORTHEAST TX...AS SHOWN BY
VAD WIND PROFILES...WILL CONTINUE TO PRODUCE STRONG LOW LEVEL
CONVERGENCE...WHILE THE MEAN LAYER 850-300 MB WIND IS SOUTHWEST
AROUND 50 KT. PWATS SHOULD CONTINUE TO INCREASE ACROSS THE REGION
TO AROUND 1.4-1.8"...AND THE LOW LEVEL FLOW WILL FEED THIS MOIST
AIR INTO THE SURFACE FRONTAL BOUNDARY AS IT MOVES SLOWLY EAST INTO
WESTERN AR. IN ADDITION THE UPPER LEVEL SHORTWAVE IS BECOMING MORE
NEGATIVELY TILTED...AND NORTHWEST AR WILL BE IN A REGION OF STRONG
DIFFLUENCE ALOFT AS THE RIGHT ENTRANCE REGION OF A 120 KT JET
MOVES OVER THE AREA.

RADAR DATA...RECENT RAINFALL HISTORY...AND HIRES MODEL GUIDANCE
SUGGEST THAT HOURLY RAIN RATES UP TO ABOUT 2" ARE LIKELY WITH
LOCAL 6-HOUR RAINFALL AMOUNTS OF 3-5". 3-HR FLASH FLOOD GUIDANCE
VALUES ARE GENERALLY 2.5-5"...BUT THEY ARE LOCALLY 2-2.5" ACROSS
THE NORTH PART OF THE AREA DUE TO RECENT HEAVY RAINS. FLASH
FLOODING IS POSSIBLE.

MCDONNAL/OTTO

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

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

LAT...LON   36689290 35659234 33699327 32179483 31949609
            32429660 33519640 34669541 36189440