MESOSCALE PRECIPITATION DISCUSSION 0216...CORRECTION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
602 PM EDT TUE MAY 17 2016
 
AREAS AFFECTED...PARTS OF SOUTHWEST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 172152Z - 180352Z
 
SUMMARY...CONVECTION FILLING IN ACROSS SOUTHWEST TX COULD EXHIBIT
HOURLY RAIN RATES UP TO 2", WITH LOCAL AMOUNTS OF 3-5".  THIS
COULD LEAD TO FLASH FLOODING.

DISCUSSION...THUNDERSTORMS ACROSS THE CONCHO VALLEY HAVE CONGEALED
INTO A COMPLEX AT THE LEADING EDGE OF AN UPPER LOW NEAR THE
WESTERN US/MEXICO BORDER.  THE STORMS HAVE BEEN MOVING
EAST-SOUTHEAST AT 20 KTS, A COMPROMISE BETWEEN THE FORWARD
PROPAGATING CONVECTIVE VECTORS AND THE MOTION OF ITS ATTENDANT
COLD FRONT.  OTHER THUNDERSTORMS HAVE BEGUN TO FORM TO THE NORTH
OF A VERY UNSTABLE AIRMASS ALONG A FRONTAL BOUNDARY IN SOUTHERN
TX.  PRECIPITABLE WATER VALUES OF 1.5-1.8" LIE ACROSS THE AREA,
WHILE INFLOW AT 850 HPA REMAINS WEAK, 10-15 KTS.  MLCAPES ARE
QUITE IMPRESSIVE ACROSS THE AREA, IN THE 2000-6000 J/KG RANGE.

THE GUIDANCE SUGGESTS THAT CONVECTION ALONG THE MORE PROGRESSIVE
NORTHERN FRONT WILL SAG SOUTH TO SOUTHEAST WITH TIME.  STORMS FROM
NORTHEAST MEXICO MIGHT CROSS THE RIO GRANDE IN THE NEXT FEW HOURS.
 FORWARD PROPAGATION TO THE EAST SHOULD BECOME HAMPERED WITH TIME
AS 850 HPA INFLOW INCREASES AND BACKS ACROSS THE RIO GRANDE
VALLEY.  AN OUTFLOW BOUNDARY MOVING INTO THE REGION FROM EARLIER
CONVECTION ALONG THE MIDDLE TX COAST -- NEAR I-37 CURRENTLY --
SHOULD ALSO ACT AS A BOUND ON ITS EASTERN EXTENT.  THE
CAM/MESOSCALE GUIDANCE HAS BEEN STRUGGLING WITH HOW FAR EAST THE
CONVECTION SHOULD EMERGE INTO CENTRAL TX.  THE AREA DEFINED IS
TOWARDS THE WESTERN SIDE OF THE GUIDANCE, WHERE THE BETTER INFLOW
AND INSTABILITY SHOULD LIE.  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 AREA AND IN DEFERENCE TO THE WIDELY SCATTERED ASPECT TO THE
HEAVY RAIN CORES INDICATED IN THE MODEL GUIDANCE (WHICH IS
SUPPORTED BY GALVEZ-DAVISON CONVECTIVE INDEX VALUES (LOW 30S)).

ROTH

ATTN...WFO...CRP...EWX...MAF...SJT...

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

LAT...LON   31300095 31260053 30519962 28659860 28159825 
            27849885 27949996 28580074 29360138 29710178 
            30650194 31100150