MESOSCALE PRECIPITATION DISCUSSION 0898...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
610 PM EDT SAT OCT 21 2017

CORRECTED FOR FIX TYPO OF I-27 IN 3RD PARAGRAPH

AREAS AFFECTED...WESTERN/CENTRAL OK...EXT NORTHWEST TX

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

VALID 212200Z - 220300Z

SUMMARY...ISOLATED FLASH FLOODING POSSIBLE THIS EVENING.

DISCUSSION...COMBINATION OF SCATTERED SUPERCELLS IN WAA REGIME IN
ADVANCE OF ADDITIONAL UPSTREAM DEVELOPMENT ASSOCIATED WITH MAIN
HEIGHT FALLS SUGGEST ISOLATED SWATHS OF 2-4" RAIN TOTALS POSING A
LOW END FLASH FLOOD RISK.

CURRENT SURFACE ANALYSIS DEPICTS A NE-SW ORIENTED COLD FRONT
SLOWLY SAGGING SOUTHWARD FROM GRANT COUNTY OK THROUGH SE ROGER
MILLS COUNTY BEFORE ANGLING MORE WESTWARD ACROSS TX PANHANDLE
BETWEEN AMA/LUB CWA BORDER. WITHIN THE WARM SECTOR 15-20KT
SOUTHERLY WINDS IS PROVIDING AMPLE GULF MOISTURE WITH TDS RISING
INTO THE MID TO UPPER 60S FOR ALL BUT THE WESTERN TWO COLUMNS OF
SW OK COUNTIES INTO FAR NORTHWEST TX. WEAK DPVA AND LOW LEVEL WAA
HAVE HELPED SUPPORT SCATTERED SUPERCELLS.  WHILE THESE CELLS ARE
IN SEVERE MODE WITH CAPABILITY OF LARGE HAIL...THERE IS SUFFICIENT
MOISTURE WITH TPWS UP TO 1.4" AND STRONG SUPERCELL ENHANCED MST
FLUX INFLOW TO SUPPORT HEAVY RAINFALL PRODUCTION WITH RATES UP TO
1.75"/HR.  FORWARD PROGRESSION IS LIKELY TO KEEP RAINFALL TOTALS
LESS THAN 2" BUT SHOULD SET THE STAGE BY WETTING THE SOILS.

THE DRIER MIXED AREA OF SW OK/TX PANHANDLE IS REPRESENTED BY AN
EASTWARD MIXING WESTERLY LOW LEVEL WIND DRY PUNCH WHERE TDS FALL
FROM UPPER 50S AT THE OK BORDER TO 30S AT OR AROUND I-27. THIS IS
ALSO ASSOCIATED WITH THE LEADING EDGE OF STRONGER MID TO UPPER
LEVEL DPVA ASSOCIATED WITH STRONG VORT OVER NE NM AND LARGE SCALE
HEIGHT FALLS.  THE BETTER HEIGHT FALLS APPROACH THE DEEPER
MOISTURE IN WESTERN OK SUPPORTING ADDITIONAL MORE N-S ORIENTED
CONVECTIVE LINE THAT WILL EXPAND/COALESCE IN SW OK IN THE 23-00Z
TIME FRAME.  IN ADDITION...AS THE COLD FRONT SAGS SOUTH A WEAK
INFLECTION WILL LIKELY BEGIN TO MANIFEST SUPPORTING A CORRIDOR OF
CELL MOTIONS ALONG/SOUTH OF THE BOUNDARY FROM SW OK TOWARD THE OKC
METRO FROM 00-03Z.  IT IS ALONG THIS INTERFACE THAT AN ADDITIONAL
2-3" TOTALS ARE POSSIBLE AND POSE THE GREATEST RISK OF FLASH
FLOODING IN THE LATE EVENING OVERNIGHT HOURS AS SOUTH OF THE LINE
QUICKER EASTWARD FORWARD PROPAGATION SHOULD LIMIT HIGHER TOTALS.
AT THIS TIME CONFIDENCE IN A PRECISE LATITUDE IS A BIT MORE
UNCERTAIN BUT A COMBINATION/BLEND OF RECENT HRRR AND 18Z
NAM-CONEST EVOLUTION APPEAR MOST FAVORABLE.   

GALLINA

ATTN...WFO...FWD...OUN...TSA...

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

LAT...LON   36629755 36419585 33989731 33719972 34799994
            35699974 36539859