MESOSCALE PRECIPITATION DISCUSSION 0420
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
723 PM EDT FRI JUN 30 2017

AREAS AFFECTED...CENTRAL/SOUTHERN OK...FAR NORTHERN TX...WESTERN
AR

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

VALID 302320Z - 010520Z

SUMMARY...WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
IMPACT CENTRAL/SOUTHERN OK...PARTS OF NORTH TEXAS AND WESTERN AR
THROUGH THE EVENING. WHILE THE CONVECTIVE MODE WILL INITIALLY BE
SEVERE...A FLASH FLOOD HAZARD MAY BECOME BETTER DEFINED LATER IN
THE EVENING.

DISCUSSION...LATE-DAY EXPERIMENTAL GOES-16 VISIBLE IMAGERY SHOWS
CLUSTERS OF HEAVY SHOWERS AND THUNDERSTORMS DEVELOPING AND
GRADUALLY BECOMING BETTER ORGANIZED JUST NORTH OF A PRE-EXISTING
AND STALLED OUT OUTFLOW BOUNDARY OVER SOUTHERN OK. MEANWHILE...A
SYNOPTIC SCALE FRONT IS GRADUALLY SETTLING SOUTH THROUGH CENTRAL
OK AND EXTENDS BACK TO THE SOUTHWEST ACROSS WEST TEXAS IN A
QUASI-STATIONARY FASHION. AREAS SOUTH AND EAST OF THIS FRONT...AND
ESPECIALLY JUST SOUTH OF THE OUTFLOW BOUNDARY ARE VERY
UNSTABLE...WITH MLCAPE VALUES OF 3500 TO 4000 J/KG JUST NORTH OF
THE RED RIVER.

MEANWHILE...THE REGION IS COMING UNDER THE INFLUENCE OF IMPROVING
RIGHT-ENTRANCE REGION JET DYNAMICS COURTESY OF A WELL-DEFINED
UPPER TROUGH CROSSING THE MIDWEST AND THE SOUTHWEST TAIL OF THIS
EXTENDING DOWN TOWARD THE OK/TX PANHANDLES. THIS COUPLED WITH
ADDITIONAL MID-LEVEL SHORTWAVE ENERGY ARRIVING THIS EVENING FROM
THE HIGH PLAINS WILL INTERACT WITH THE VERY UNSTABLE AIRMASS
INCLUDING A MOISTURE-RICH BOUNDARY LAYER WITH LOW TO MID 70
DEWPOINTS FOR WIDESPREAD CONVECTION.

WHILE THE INITIAL CONVECTIVE MODE WILL TEND TO BE SEVERE OVER
CENTRAL/SOUTHERN OK...WESTERN AREAS OF NORTH TEXAS AND AS FAR EAST
AS WESTERN AR...WITH SEVERAL SUPERCELL STRUCTURES...THE CONVECTION
SHOULD GRADUALLY CONSOLIDATE/MERGE LATER IN THE EVENING AND
ESPECIALLY WITH A PHASING OF THE SYNOPTIC AND MESOSCALE OUTFLOW
BOUNDARIES. IN TIME...THE MERGING OF CONVECTION WILL TEND TO
FOSTER A LINEAR MCS IN A WSW/ENE FASHION THAT WILL BEGIN TO BOW
EAST-SOUTHEAST AND EVENTUALLY IMPACT AREAS CLOSER TO THE RED
RIVER. THIS WILL BE AIDED FURTHER BY THE ARRIVAL OF THE UPSTREAM
SHORTWAVE ENERGY AND ANY ASSOCIATED CONVECTION THAT WILL BE
ATTEMPTING TO CROSS THE OK/TX PANHANDLES.

THEREFORE...DESPITE THE DRY ANTECEDENT CONDITIONS ACROSS MUCH OF
THE REGION CURRENTLY...THE PERSISTENT MODE OF CONVECTION THIS
EVENING ALONG WITH INTENSE RAINFALL RATES TO OVER 2 INCHES/HR AND
SOME TRAINING CONVECTIVE CELL THREAT...MAY ALLOW FOR A FLASH FLOOD
HAZARD TO EVOLVE AT LEAST LOCALLY THIS EVENING. THE URBANIZED
AREAS WOULD BE THE MOST SENSITIVE TO THIS THREAT. EXPECT AS MUCH
AS 3 TO 6 INCHES OF RAIN IN SOME AREAS THAT WILL DRIVE THIS
CONCERN. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...AMA...FWD...LUB...LZK...OUN...SHV...SJT...TSA...

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

LAT...LON   36209397 35799331 35259333 34499417 34119510
            33879577 33719650 33479756 33259868 33040012
            33160082 33700090 34170068 34680010 34989971
            35379884 35659786 35839660 35949572 36079503