MESOSCALE PRECIPITATION DISCUSSION 0281
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
539 PM EDT SUN MAY 28 2017

AREAS AFFECTED...CENTRAL TX...NORTHEAST TX...EXTREME SW AR...NW LA

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

VALID 282138Z - 290138Z

OVERVIEW...STRONG THUNDERSTORMS DEVELOPING FROM JUST EAST OF BIG
BEND TX ALONG A LINE TO NORTHEAST TX WILL INCREASE DURING THE NEXT
FEW HOURS. THESE STORMS COULD RESULT IN LOCAL FLASH FLOODING.

DISCUSSION...STRONG THUNDERSTORMS ARE DEVELOPING ALONG A FRONTAL
BOUNDARY THAT EXTENDS NORTHEAST FROM NEAR DEL RIO TO JUST SOUTH OF
TEXARKANA. THESE STORMS ARE PRODUCING LOCAL HOURLY RAIN RATES OF
1-3". RADAR INDICATES THAT LOCAL RAINFALL TOTALS OF 3" HAVE
ALREADY FALLEN WHERE THE STRONGEST STORMS ARE OCCURRING
CURRENTLY... ALONG THE SOUTHWEST AND NORTHEAST PORTIONS OF THE
FRONTAL BOUNDARY ACROSS TX.

SURFACE DEW POINTS ARE MAINLY 70 DEGREES F AND HIGHER ACROSS THE
REGION...WITH PRECIPITABLE WATER AROUND 1.5-2.0" LOW LEVEL
SOUTHERLY FLOW OF 15-20 KT WILL CONTINUE TO FEED MOISTURE INTO THE
REGION. SPC MESOANALYSES SHOW A VERY UNSTABLE ENVIRONMENT WITH
MUCAPE IN THE RANGE OF 4000-6000 J/KG. IN ADDITION CIN THAT WAS
ACROSS THE REGION EARLIER HAS MOSTLY ERODED DURING THE LAST 3
HOURS.

SO CONDITIONS ARE FAVORABLE FOR CONVECTION TO CONTINUE...AND IT
WILL PROBABLY FILL IN ALONG MUCH OF THE BOUNDARY DURING THE NEXT
COUPLE HOURS. WITH THE MOVEMENT OF THE STORMS ALONG THE
BOUNDARY...AND ADDITIONAL CONVECTION DEVELOPING JUST TO THE
SOUTHWEST IN THE STATE OF COAHUILA MEXICO...THERE IS GOOD
POTENTIAL FOR TRAINING AND REPEAT STORMS. OVER THE NEXT FOUR HOURS
THE EASTERN END OF THE COMPLEX COULD EXTEND INTO EXTREME SE AR AND
NORTHEAST LA...SO THEY HAVE BEEN INCLUDED IN THE MPD AS WELL.

HIRES MODELS AGREE RATHER WELL ON THE POTENTIAL FOR HEAVY RAIN
ACROSS THE AREA. THE HRRR...NAM...NAM CONEST...ARW...AND NSSL WRF
ALL SHOW LOCAL AREAS OF 4" TOTAL RAINFALL. SOME OF THE MODELS SHOW
LOCAL TOTALS AS HIGH AS 6". THE 3 HOUR FLASH FLOOD GUIDANCE ACROSS
THE THREAT AREA IS GENERALLY 3-5"...SO LOCALIZED FLASH FLOODING IS
POSSIBLE.

MCDONNAL

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...SJT...

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

LAT...LON   33319384 32779332 32229310 31849310 31229349
            30759413 30419524 29889707 29639860 29429985
            29430068 29720080 30839964 32779642 33179504