MESO: Nws Weather Prediction Center College Park Md

AWUS01 KWNH 192205
FFGMPD
TXZ000-200203-

MESOSCALE PRECIPITATION DISCUSSION 0260
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
604 PM EDT THU SEP 19 2013

AREAS AFFECTED...PORTIONS OF CENTRAL TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 192203Z - 200203Z

SUMMARY...MODERATE TO HEAVY RAINFALL IS EXPECTED TO OCCUR FOR THE
NEXT SEVERAL HOURS IN A VERY MOIST ENVIRONMENT WITH LOW FLASH
FLOOD GUIDANCE VALUES. REGIONAL FLASH FLOODING IS CONSIDERED
LIKELY INTO THIS EVENING.

DISCUSSION...MID- AND UPPER-LEVEL MOISTURE FROM TROPICAL CYCLONE
MANUEL IS OVERRIDING THE AREA, WHILE MODEST LOW-LEVEL INFLOW FROM
THE GULF OF MEXICO INVADES BELOW, ON THE ORDER OF 20-25 KNOTS.
PRECIPITABLE WATER VALUES OF AROUND TWO INCHES RESIDE IN THE AREA,
WHICH IS IN THE 99TH PERCENTILE FOR MID TO LATE SEPTEMBER. A
SURFACE BOUNDARY RUNS FROM CENTRAL TX SOUTHWEST TOWARDS DEL RIO,
WHICH IS ACTING AS THE FOCUS FOR THE OVERRUNNING OF GULF OF MEXICO
INFLOW. RIDGING ALOFT EXISTS AHEAD OF AN UPPER LEVEL TROUGH
MOVING THROUGH THE NORTHERN ROCKIES. A SATURATED ATMOSPHERE WITH
CAPE VALUES RUNNING AROUND 500 J/KG IS ALLOWING FOR WARM RAIN
PROCESSES TO BE AT PLAY HERE, AND RECENT SATELLITE ENHANCEMENT
IMPLIES AN UPTICK TO THE CURRENT PRECIPITATION INTENSITY. RECENT
RAINFALL HAS DROPPED FLASH FLOOD GUIDANCE VALUES TO AROUND TWO
INCHES IN THREE HOURS, WHICH HAS BEEN LOCALLY EXCEEDED AS OF LATE.
NO LET UP IN THE LOW-LEVEL INFLOW IS EXPECTED INTO TONIGHT. IN
SOME ASPECTS, THIS OVERALL SETUP APPEARS SIMILAR TO THAT WITNESSED
OVER COLORADO LAST WEEK. REGIONAL FLASH FLOODING IS CONSIDERED
LIKELY HERE.

ROTH

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FWD...EWX...SJT...MAF...

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

LAT...LON 30560251 32050080 32119902 30859911 29640084 29720213
30560251

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