MESOSCALE PRECIPITATION DISCUSSION 0704
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
450 PM EDT SUN SEP 25 2016
 
AREAS AFFECTED...HILL COUNTRY OF CENTRAL AND SOUTHWEST TX 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 252050Z - 260050Z
 
SUMMARY..THE MAIN THREAT FOR FLASH FLOODING SHIFTS EAST WITH THE
MCV...BUT VERY LOW FLASH FLOOD GUIDANCE VALUES SUGGEST AT LEAST AN
ISOLATED THREAT REMAINS INTO THE EARLY EVENING HOURS FURTHER WEST
INTO THE HILL COUNTRY. 

DISCUSSION....MOST OF THE CONVECTION ACROSS SOUTH CENTRAL TX IS
TIED TO THE POSITION OF THE MCV...WHERE NEWLY DEVELOPED CONVECTION
IS STRENGTHENING (BASED ON THE COOLING TOPS SEEN ON THE IR LOOP).
THE KDFX HAS SHOWN HOURLY RAINFALL RATES NEAR 1.50 INCHES WITH THE
DEVELOPING CONVECTION...WHICH IS TAPPING 1000 J/KG MLCAPE AND NEAR
2.00 INCH PRECIPITABLE WATER AIR. 

THE LOW LEVEL INFLOW SHOULD CONTINUE TO SUPPLY MOISTURE TO THE
LIFT AHEAD OF THE MCV...AND THE LATEST RAP SUGGESTS THAT THE
INSTABILITY IS EXPECTED TO REMAIN IN THE 1000 J/KG RANGE THROUGH
AT LEAST 01Z. THE MID LEVEL FLOW HAS BEEN WEAKENING THIS
AFTERNOON... BUT REMAINS QUASI UNIDIRECTIONAL...WHICH WOULD
SUPPORT TRAINING AND LOCAL CELL MERGERS. TRAINING AND MERGERS
COULD FOSTER LOCAL HOURLY RAINFALL RATES BETWEEN 1.50 AND 2.00
INCHES ASSOCIATED WITH THE MCV. 

THE LATEST HRRR/EXPERIMENTAL HRRR ARE SHOWING LOCAL 3-5 INCH
RAINFALL AMOUNTS ASSOCIATED WITH THE CONVECTION OVER PORTIONS OF
SOUTH CENTRAL TX...BUT THESE AMOUNTS COULD BE OVERDONE...AS THE
INSTABILITY MAY NOT BE ABLE TO SUPPORT SUFFICIENTLY DEEP
CONVECTION TO PRODUCE THESE AMOUNTS. HOWEVER...ONE HOUR FLASH
FLOOD GUIDANCE VALUES ARE AS LOW AS 1.00 TO 1.50 INCHES NEAR THE
MCV...SO THERE IS A THREAT FOR FLASH FLOODING INTO EARLY THIS
EVENING.

FURTHER WEST...WHERE FLASH FLOOD GUIDANCE VALUES UNDER AN
INCH...THE INSTABILITY HAS BEEN TEMPORARILY EXHAUSTED DUE TO THE
PRESENCE OF THE COLD POOL. HOWEVER...THE LATEST VISIBLE IMAGES
SUGGEST CLEARING IS OCCURRING...WHICH COULD ALLOW FOR 
DESTABILIZATION. ANY ADDITIONAL CONVECTION DEVELOPMENT COULD
AGGRAVATE ONGOING FLOODING IN AREAS WITH SATURATED SOILS... SO A
FLASH FLOOD THREAT REMAINS HERE AS WELL. 

HAYES

ATTN...WFO...EWX...SJT...

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

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