MESOSCALE PRECIPITATION DISCUSSION 0824
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
941 AM EDT MON SEP 25 2017

AREAS AFFECTED...WEST-CENTRAL/NORTHWEST TX...WESTERN
OK...CENTRAL/SOUTHERN KS

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

VALID 251340Z - 251940Z

SUMMARY...SOME INCREASE IN COVERAGE OF HEAVY SHOWERS AND
THUNDERSTORMS IS EXPECTED OVER THE NEXT FEW HOURS. GIVEN THE
INCREASED CONVECTIVE ORGANIZATION AND HEAVIER RAINFALL
RATES...SOME FLASH FLOODING WILL BE POSSIBLE.

DISCUSSION...GOES-WV IMAGERY SHOWS A WELL-DEFINED UPPER TROUGH
CONTINUING TO SLOWLY PIVOT EAST ACROSS THE INTERMOUNTAIN
WEST...WITH EVIDENCE OF A SHORTWAVE TROUGH AND ASSOCIATED JET
STREAK LIFTING NORTHEAST ACROSS CENTRAL/NORTHERN NM.

THE ENERGY IS FOSTERING AN INCREASINGLY DIVERGENT FLOW REGIME
ALOFT WHICH IS INTERACTING WITH A STRONG FRONTAL ZONE OVER THE
HIGH PLAINS ALONG WITH AN INCREASINGLY MOIST COLUMN ALONG IT WHICH
IS BEING AIDED BY MID/HIGH LEVEL MOISTURE FROM T.S. PILLAR OVER
THE EASTERN PACIFIC JUST SOUTHWEST OF MAINLAND MEXICO. THE ONE
FACTOR THAT TENDS TO BE MITIGATING THE RAINFALL POTENTIAL IS THE
RELATIVELY MODEST INSTABILITY PARAMETERS ALONG AND JUST AHEAD OF
THE FRONT WHICH ARE GENERALLY ON THE ORDER OF 500 TO 1000 J/KG OF
MLCAPE. HOWEVER...THE ARRIVAL OF STRONGER UPPER FORCING WILL HELP
COMPENSATE...AND ALREADY THERE HAS BEEN SOME SLOW UPTICK IN
CONVECTIVE ORGANIZATION OVER THE LAST HOUR ACROSS AREAS OF
NORTHWEST TEXAS AND STRETCHING NORTHEAST INTO SOUTH-CENTRAL KS.

THE HRRR-TLE OUTPUT ALONG WITH HRRR/HRRRX GUIDANCE SUPPORTS SOME
FURTHER UPTICK IN CONVECTIVE COVERAGE ALONG WITH HEAVIER RAINFALL
RATES OVER THE NEXT SEVERAL HOURS. RAINFALL RATES OF UP TO 1.5
INCHES/HR...AND STORM TOTALS THROUGH EARLY TO MID-AFTERNOON OF AS
MUCH AS 2 TO 4 INCHES ARE EXPECTED. SOME ISOLATED AMOUNTS POSSIBLY
AROUND 5 INCHES WILL BE POSSIBLE GIVEN RELATIVELY SLOW CELL MOTION
AND SOME PERIODIC TRAINING OF CELLS. GIVEN THESE AMOUNTS...SOME
FLASH FLOODING WILL BE POSSIBLE.

ORRISON

ATTN...WFO...AMA...DDC...ICT...LUB...OUN...TOP...

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

LAT...LON   39119857 38849720 37349727 35839789 34809858
            33739968 33010082 33000174 33540264 34480303
            35320272 36590109 37700011