MESOSCALE PRECIPITATION DISCUSSION 0258
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
725 PM EDT FRI AUG 08 2014
 
AREAS AFFECTED...AR...SE OK...FAR NE TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 082323Z - 090223Z
 
SUMMARY...VERY INTENSE RAIN RATES MAY LEAD TO FLASH FLOODING IN
CENTRAL AND WESTERN ARKANSAS AND ADJACENT OK/TX THROUGH MID
EVENING.

DISCUSSION...THE ENVIRONMENT WAS IMPRESSIVELY CONDUCIVE TO HEAVY
RAIN WITH DEWPOINTS IN THE UPPER 70S AND PRECIPITABLE WATER AROUND
2 INCHES IN THE PRE-CONVECTIVE ENVIRONMENT HERE. DUAL POL
INFORMATION FROM KSRX AND KLZK SHOWED AN UNUSUAL BREADTH OF HEAVY
RAIN CLASSIFICATION FROM THE HHC. A DROP OF REFLECTIVITY FROM
HIGHER VALUES ALOFT TO NEAR 50 DBZ AT THE BASE TILTS...COMBINED
WITH MODERATELY HIGH KDP VALUES CLOSE TO 3 DEGREEES / KM...SUPPORT
THE NOTION THAT THE THREE-PLUS INCH PER HOUR ESTIMATES FROM KSRX
ARE NOT OVERESTIMATES...AND ARE LIKELY CLOSE TO REALITY.

WITH TIME SOME LOCAL COLD POOL DEVELOPMENT HAS BEEN DRIVING THE
LEADING LINE FORWARD...REDUCING RESIDENCE TIME OVER A GIVEN
LOCATION. THIS SUGGESTS THE HEAVIEST RAIN TOTALS MAY HAVE ALREADY
OCCURRED...BUT THERE IS SOME CONCERN FOR REDEVELOPMENT AND
TRAINING ALONG THE WESTERN FLANK...AS SOUTHWESTERLY INFLOW AND
WARM ADVECTION PROFILES WILL PERSIST. THE 12Z WRF ARW AND RECENT
HRRR RUNS ALL SUGGEST A DECREASE OF INTENSITY NEAR
02Z...COINCIDING WITH THE SMALL MCS NEARING THE UPPER RIDGE CENTER
OVER NE TX/SRN AR...ALONG WITH THE LOSS OF HEATING. UNTIL THAT
TIME...STEERING WINDS MAY TAKE THE SMALL MCV SSE WHILE CORFIDI
VECTORS SUGGEST SOME PROPAGATION S OR TURNING SW. SEE SPC
MESOSCALE DISCUSSION 1527 FOR FURTHER DETAILS.

BURKE

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

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

LAT...LON   33219459 33749556 34679575 35499499 35719318 35019220
            34159203 33499247 33299315 33219459