MESOSCALE PRECIPITATION DISCUSSION 0217
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
825 PM EDT TUE MAY 17 2016
 
AREAS AFFECTED...PARTS OF SOUTHERN TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 180024Z - 180354Z
 
SUMMARY...CONVECTION FILLING IN ACROSS SOUTHERN TX COULD EXHIBIT
HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS OF 3-5".  THIS
COULD LEAD TO FLASH FLOODING.

DISCUSSION...THUNDERSTORMS ARE OCCASIONALLY FORMING/MERGING OVER
THE TOP OF A PROGRESSIVE COLD FRONT MOVING THROUGH SOUTHERN TX. 
PRECIPITABLE WATER VALUES OF 1.6-1.9" LIE ACROSS THE AREA WHILE
INFLOW AT 850 HPA HAS INCREASED TO 20-30 KTS.  MLCAPES ARE QUITE
IMPRESSIVE ACROSS THE AREA, IN THE 3000-4500 J/KG RANGE.

THE GUIDANCE SUGGESTS THAT THE FRONT WILL CONTINUE SAGGING
SOUTHWARD WHILE 850 HPA INFLOW  BACKS, WHICH SHOULD RELATIVELY
ANCHOR MOST THUNDERSTORM ACTIVITY ONCE IT FORMS.  ANY CELLS THAT
MOVE (SOUTH-SOUTHEAST HAS BEEN THE RECENT PROPAGATION IN THE
REGION) COULD LEAD TO CELL MERGERS WITH NEW ACTIVITY, SUCH AS HAS
BEEN WITNESSED OCCASIONALLY ACROSS PORTIONS OF SOUTHWEST TX OVER
THE PAST SEVERAL HOURS.  THE CAM/MESOSCALE GUIDANCE HAS BEEN
INCONSISTENT ON CONVECTIVE FORMATION AND PLACEMENT IN SOUTHERN TX.
 HOURLY RAIN RATES TO 2", WITH LOCAL AMOUNTS OF 3-5", COULD LEAD
TO FLASH FLOODING.  USED POSSIBLE WORDING DUE TO THE RELATIVE HIGH
FLASH FLOOD GUIDANCE VALUES IN THIS REGION AND IN DEFERENCE TO THE
WIDELY SCATTERED ASPECT TO THE HEAVY RAIN CORES INDICATED IN THE
MODEL GUIDANCE WHICH APPEAR TO BE CAPTURING ONGOING ACTIVITY
(WHICH IS SUPPORTED BY GALVEZ-DAVISON CONVECTIVE INDEX VALUES (LOW
30S)).

ROTH

ATTN...WFO...BRO...CRP...

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

LAT...LON   27929964 27929883 27899845 27609822 26419784 
            26019784 26029824 26319895 26389915 26819941 
            27149955 27519957 27809987