Post by SKYSUMMIT on Apr 16, 2015 20:10:25 GMT -6
MESOSCALE PRECIPITATION DISCUSSION 0044
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1002 PM EDT THU APR 16 2015
AREAS AFFECTED...SOUTHEAST TX
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 170202Z - 170602Z
SUMMARY...INSTABILITY AND ONGOING 0-3 KM SHEAR SHOULD ALLOW
THUNDERSTORMS WITH HEAVY RAIN RATES TO PERSIST FOR SEVERAL MORE
HOURS. CONSIDERING SATURATED SOILS, FLASH FLOODING IS LIKELY.
DISCUSSION...A VERY MOIST AND UNSTABLE AIRMASS COMBINED WITH
SUFFICIENT CLOUD BASE INFLOW HAS LED TO SIGNIFICANT RAINFALL OVER
THE REGION OVER THE PAST EIGHT HOURS. REPORTS FROM THE JEFFERSON
COUNTY TX MESONET INDICATE A HANDFUL OF SITES WITH 5"+ OF RAIN,
WITH ONE SITE APPROACHING 8". INFLOW AT 850-700 HPA IS AROUND 25
KTS OUT OF THE SOUTH-SOUTHWEST, CLOSE TO THE MAGNITUDE OF THE
850-400 HPA MEAN WIND, WHILE SURFACE WINDS ARE EAST-NORTHEAST DUE
TO THE FORMATION OF A COLD POOL ACROSS SOUTHEAST TX AND SOUTHWEST
LA. PRECIPITABLE WATER VALUES OF 1.8-2" EXIST ACROSS THE REGION
PER GPS INFORMATION, WHICH IS SUPPORTIVE OF 2" AN HOUR RAIN RATES
WHERE CELLS STALL AND/OR TRAIN. THE 00Z CORPUS CHRISTI TX
SOUNDING SHOWED 4538 J/KG CAPE WITHIN A CAPPED AIRMASS ACROSS
SOUTHERN TX, WHERE 700 HPA TEMPERATURES APPROACH 10C.
THE BULK OF THE HEAVY RAINFALL EPISODE COULD END FROM WEST TO EAST
OVER THE NEXT SEVERAL HOURS, URGED ONWARD BY A SEVERE THUNDERSTORM
COMPLEX MOVING INTO AUSTIN COUNTY. HOWEVER, LOW-LEVEL INFLOW IS
FORECAST TO INCREASE AND SIGNIFICANT CAPE IS EXPECTED TO PERSIST
OVERNIGHT, CASTING DOUBT CONCERNING A QUICK END TO THIS HEAVY RAIN
EVENT. CONVECTION COULD BECOME MORE ELEVATED OVER THE BOUNDARY
DURING THE NEXT HOUR OR TWO WHICH COULD LEAD TO SOME NORTHWARD
RETURN OF HEAVY RAIN CORES. MUCH OF THE MESOSCALE GUIDANCE
INDICATES AN ADDITIONAL 3-5" LOCALLY IS POSSIBLE OVERNIGHT.
CONSIDERING HOW MUCH RAIN HAS ALREADY FALLEN, FLASH FLOODING IS
CONSIDERED LIKELY.
ROTH
