Graphic for MPD #0828

MESOSCALE PRECIPITATION DISCUSSION 0828
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
958 AM EDT TUE SEP 26 2017

AREAS AFFECTED...NW TEXAS...SW AND SC OKLAHOMA

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

VALID 261353Z - 261900Z

SUMMARY...LOCALIZED FLASH FLOODING IS POSSIBLE IN A REGION OF
LOW-LEVEL CONVERGENCE OVER NW TX AND SW/SC OK THAT WILL BE SLOWLY
SHIFTING SOUTHEAST WITH TIME TODAY.

DISCUSSION...AT 1330Z REGIONAL RADARS AND SATELLITE IMAGERY
INDICATED A CORRIDOR OF GRADUALLY GROWING CONVECTIVE ACTIVITY
ACROSS NORTHWEST TEXAS AND SOUTHWEST OKLAHOMA. THIS WAS ASSOCIATED
WITH ENHANCED LOW-LEVEL MOISTURE FLUX CONVERGENCE ON A BOUNDARY
THAT IS LIKELY A COMPOSITE OF AN EXISTING QUASI-STATIONARY FRONT
AND OUTFLOW BOUNDARIES FROM OVERNIGHT CONVECTION TO THE NORTHWEST
(IN ERN NM AND TX PANHANDLE). IR SATELLITE IMAGERY SHOWS POCKETS
OF SLOWLY COOLING CLOUD TOPS...LIKELY A REFLECTION OF THE LIMITED
INSTABILITY ACROSS THE REGION WITH RAP ANALYSIS SHOWING MUCAPE
AROUND 500 J/KG. INSTABILITY LEVELS MAY NOT INCREASE MUCH THROUGH
THE MORNING AND EARLY AFTERNOON HOURS GIVEN ABUNDANT CLOUD
COVER...BUT THE FIRST FEW FRAMES OF VISIBLE SATELLITE IMAGERY
SHOWED SOME POCKETS OF CLEARING TO THE SOUTHEAST OF ONGOING
CONVECTION. THEREFORE...IT MAY BE POSSIBLE TO PUSH MUCAPE UP TO
AROUND 1000 J/KG IN THE SOUTHEAST PART OF THE OUTLINED DISCUSSION
AREA BY EARLY AFTERNOON...AND CONVECTION SHOULD HAVE A TENDENCY TO
DRIFT SOUTHEAST WITH TIME.

THE MOST FOCUSED AREA OF CONVECTION THUS FAR HAS BEEN NEAR THE RED
RIVER ON THE WESTERN OK-TX BORDER. THERE WERE SOME HINTS IN KFDR
REFLECTIVITY LOOPS THAT A WEAK MCV MAY BE DEVELOPING NEAR OR JUST
SW OF ALTUS OK...AND A BAND OF CONVECTION APPEARED TO BE
ORGANIZING ON THE E/SE FLANK. IT APPEARS THAT KFDR DUAL POL VALUES
ARE UNDERESTIMATING RAINFALL RATES...WITH THE VERNON TX AWOS
(KF05) RECORDING 1.53 IN/HR BETWEEN 7-8 AM LOCAL TIME. HIGHEST
ESTIMATES FROM KFDR WITHIN A FEW MILES OF THE OBSERVATION SITE
WERE AROUND 1 IN/HR. GIVEN THE LOCALIZED FORCING FROM THE POSSIBLE
MCV...FOCUSED BANDS OF CONVECTION MAY PERSIST FOR ANOTHER 1-3
HOURS FROM NEAR LAWTON OK TO NEAR SEYMOUR TX. THIS COULD LEAD TO
RAIN RATES POSSIBLY UP TO 2 IN/HR GIVEN THE OBSERVATIONAL HISTORY
AT VERNON...AND LOCALIZED FLASH FLOODING.

ELSEWHERE IN THE DISCUSSION AREA...CONVECTION SHOULD CONTINUE TO
GRADUALLY DEVELOP ALONG AND AHEAD OF THE NEAR-SURFACE BOUNDARY.
THE LAST SEVERAL RUNS OF THE OPERATIONAL HRRR SHOW INCREASING RAIN
RATES FROM NEAR MIDLAND TX TO NEAR WICHITA FALLS TX BY
15-16Z...AND THEN GRADUALLY DRIFTING TO THE SOUTHEAST WITH TIME IN
THE AFTERNOON HOURS. LOCALIZED FLASH FLOODING COULD DEVELOP IN
AREAS WHERE CONVECTION MANAGES TO TRAIN FOR A COUPLE HOURS...GIVEN
RAIN RATES OF 1-2 IN/HR. STORMS MAY BECOME MORE EFFICIENT RAINFALL
PRODUCERS IF GREATER INSTABILITY CAN DEVELOP...AND MODIFIED RAP
SOUNDINGS FROM NEAR ABILENE SUGGEST 1000 J/KG CAPE WOULD BE
ACHIEVABLE WITH ONLY MODEST SURFACE TEMPERATURE INCREASES TO
AROUND 72-74 DEGREES.

LAMERS

ATTN...WFO...FWD...LUB...MAF...OUN...SJT...

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

LAT...LON   35149791 34909720 34699673 34419646 34009693
            33509752 33119803 32209913 31689992 31350078
            31220172 31300234 31710278 32130282 32440274
            32800241 33080202 33680119 34060051 34599965
            34929885


Last Updated: 958 AM EDT TUE SEP 26 2017