MESOSCALE PRECIPITATION DISCUSSION 0567
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
834 PM EDT THU OCT 08 2015
 
AREAS AFFECTED...TEXAS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090025Z - 090600Z
 
SUMMARY...VERY HEAVY AND SLOW-MOVING SHOWERS AND THUNDERSTORMS IS
EXPECTED TO CONTINUE TO IMPACT PORTIONS OF THE MIDDLE RIO GRANDE
VALLEY AND SOUTH-CENTRAL TEXAS WELL INTO THE OVERNIGHT HOURS. THE
SLOW CELL MOTION COUPLED WITH INTENSE RAINFALL RATES WILL MAKE
FLASH FLOODING POSSIBLE.

DISCUSSION...NO SIGNIFICANT LARGE SCALE CHANGES OF NOTE THE LAST
FEW HOURS AS AN UPPER LOW OVER NORTHERN MEXICO CONTINUES TO FOSTER
A BROAD AREA OF DIVERGENT FLOW ALOFT OVER MUCH OF SOUTHWEST TEXAS
AS SEEN IN THE LATEST IR/WV SATELLITE IMAGERY. THIS IS AGAIN
FOCUSING AN AREA OF STRONGER DEEP LAYER ASCENT AND IS INTERACTING
WITH AT LEAST A MODEST FETCH OF LOW LEVEL SOUTHEAST FLOW THAT IS
BECOMING MORE MOIST WITH TIME. THE PW ANOMALIES AS PER THE 12Z GFS
ARE RUNNING ABOUT 1.5 TO 2 STANDARD DEVIATIONS ABOVE NORMAL...WITH
VALUES AS PER GPS-DERIVED DATA NOW AS HIGH AS 1.5 TO 1.7 INCHES.
THE RESULT HAS BEEN A BROKEN AXIS OF SLOW-MOVING SHOWERS AND
THUNDERSTORMS WHICH HAS BEEN AIDED BY BY 1500 TO 2000 J/KG OF
MUCAPE.

CLOUD TOP TEMPERATURES HAVE COOLED A BIT OVER THE LAST COUPLE OF
HOURS SUGGESTING MORE VIGOROUS CONVECTIVE GROWTH/FORCING...AND THE
GLD-360 LIGHTNING DENSITY PRODUCT SHOWS SOME INTENSE STRIKE
ACTIVITY WITH MULTIPLE CORES INCLUDING AN ESPECIALLY STRONG CORE
CROSSING THE RIO GRANDE RIVER JUST SOUTHEAST OF DEL RIO. THESE
TRENDS SUGGEST INTENSE RAINFALL RATES...AND LATEST DUAL-POL
ESTIMATES SUGGEST RAINFALL RATES OF 2 TO 2.5 INCHES/HR WITH THE
STRONGER CELLS.

OVER THE NEXT SEVERAL HOURS...HIGHER PW VALUES DOWN ALONG THE RIO
GRANDE VALLEY AND AT LEAST A MODESTLY UNSTABLE AIRMASS SHOULD
CONTINUE TO FOSTER STRONG CONVECTION WITH HEAVY RAINFALL
POTENTIAL. THE CONVECTION AS PER THE LATEST RUNS OF THE HRRR AND
THE 12Z ARW/12Z NSSL-WRF SOLUTIONS SHOW CONVECTION BEGINNING TO
CONCENTRATE ITSELF MUCH MORE DOWN ALONG THE MIDDLE RIO GRANDE
VALLEY WITH A TENDENCY FOR CONVECTION TO WEAKEN FARTHER NORTH
WHERE LOWER DEWPOINTS AND A COOLING BOUNDARY LAYER WILL PROVIDE
INCREASING STABILITY. 

EXPECT RAINFALL AMOUNTS OF AS MUCH AS 3 TO 5 INCHES TO BE
POSSIBLE...AND ESPECIALLY AREAS CLOSER TO THE RIO GRANDE RIVER.
FLASH FLOODING WILL BE POSSIBLE AS A RESULT. WILL CONTINUE TO
MONITOR. 

ORRISON

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

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

LAT...LON   31619990 30719912 29199899 27929927 27679975 
            27920025 28220055 29110121 29720173 30390170 
            30880137 31550058