MESOSCALE PRECIPITATION DISCUSSION 0727
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1129 AM EDT FRI AUG 25 2017

AREAS AFFECTED...NORTHWEST TX & SOUTHWEST OK

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

VALID 251528Z - 251928Z

SUMMARY...THUNDERSTORMS ARE ATTEMPTING TO CONGEAL ACROSS NORTHWEST
TX AND SOUTHWEST OK.  HOURLY RAIN TOTALS UP TO 2.5" WITH LOCAL
AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...AN AREA OF PERSISTENT THUNDERSTORMS ACROSS SOUTHWEST
OK ARE BEING JOINED BY NEW ACTIVITY IN NORTHWEST TX.  A SHORTWAVE
MOVING INTO THE TX PANHANDLE IS PROVIDING UPPER LEVEL DIVERGENCE
ACROSS THE REGION.  PRECIPITABLE WATER VALUES ARE ~2".  INFLOW AT
850 HPA IS CONVERGENT AT ~10 KTS PER VAD WIND PROFILES.  EFFECTIVE
BULK SHEAR IN SOUTHWEST OK IS ~25 KTS PER SPC MESOANALYSES.

THE MESOSCALE GUIDANCE HAS A GENERAL SIGNAL FOR SPOTTY LOCAL
AMOUNTS OF 3-4" IN THIS AREA.  TWO WEEK RAIN TOTALS OVER THE AREA
ARE GENERALLY 300-400% OF NORMAL; SOILS ARE PARTIALLY SATURATED
WHICH IS SOMEWHAT REFLECTED IN THE THREE HOURLY FLASH FLOOD
GUIDANCE.  THE EXPECTATION, BASED ON THE SIGNAL IN THE 06Z SSEO
NEIGHBORHOOD PROBABILITIES AS WELL AS THE 850 HPA MASS FIELDS,
SUGGEST THAT THE AXIS OF 850 HPA CONVERGENCE IS EXPECTED TO WEAKEN
AROUND 19Z, WHICH SHOULD ALLOW CONVECTION TO BECOME LESS
CONCENTRATED/ MORE SCATTERED DESPITE INCREASING INSTABILITY
BECOMING AVAILABLE CLOSE TO THE OUTFLOW BOUNDARY/WEAK THERMAL
GRADIENT IN NORTHWEST TX.  HOURLY RAIN RATES UP TO 2.5" ARE
EXPECTED.

ROTH

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

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

LAT...LON   35899714 33489732 32109812 31330001 31790070
            33590051 35509902