Graphic for MPD #0787

MESOSCALE PRECIPITATION DISCUSSION 0787
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
405 PM EDT FRI SEP 08 2017

AREAS AFFECTED...SOUTHERN NV....SOUTHEAST CA...WESTERN AZ

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 082005Z - 090205Z

SUMMARY...DEVELOPING SHOWERS AND THUNDERSTORMS COULD PRODUCE HEAVY
RAINFALL WITH THE POTENTIAL FOR FLASH FLOODING.

DISCUSSION...DAYTIME HEATING HAS LED TO DEVELOPMENT OF SHOWERS AND
THUNDERSTORMS IN SOUTHEAST CA TO WESTERN AZ AND SOUTHERN NV.

THE MODELS AND 18Z SOUNDINGS FROM LAS VEGAS AND YUMA AZ SHOW ABOVE
NORMAL MOISTURE WITH THE YUMA SOUNDING INDICATING 1.6 INCHES OF
PRECIPITABLE WATER.  THESE VALUES ARE 1-2 STD DEVIATIONS ABOVE
NORMAL.  THE ABOVE NORMAL MOISTURE COMBINED WITH THE CAPE VALUES
OF 2000-3000 J/KG FROM THE YUMA SOUNDING SHOW PLENTY OF AVAILABLE
INSTABILITY.

THERE WERE EARLIER SHOWERS IN LAS VEGAS SO ADDITIONAL SHOWERS
DEVELOPING IN THE AREA COULD LEAD TO FLOODING PROBLEMS NOW THAT
SOILS HAVE BECOME WETTER.

ADDITIONAL SHOWERS ARE FORECAST TO DEVELOPING FURTHER SOUTH INTO
SOUTHEAST CA AND WESTERN AZ...INCLUDING IN TERRAIN.
THE OBSERVED AND FORECAST SOUNDINGS ACROSS SOUTHEAST CA/WESTERN
AZ/SOUTHERN NV INDICATE DEEP SOUTHERLY FLOW.  THIS PROMOTES SOUTH
TO NORTH MOVEMENT.

GIVEN LITTLE DIRECTIONAL WIND SHEAR...
PERIOD OF TRAINING CELLS ARE POSSIBLE.  WHERE TRAINING
OCCURS...AMOUNTS OF 1-2 INCHES ARE POSSIBLE....SUPPORTED BY THE
12Z WRF ARW AND NSSL WRF. THUS SOME FLASH FLOODING WILL BE
POSSIBLE.

PETERSEN

ATTN...WFO...FGZ...PSR...SGX...SLC...TWC...VEF...

ATTN...RFC...CBRFC...CNRFC...

LAT...LON   37971488 37971407 37851305 37551210 37251144
            36721108 36301063 35591042 35331067 35551161
            35681237 35211262 33861241 32251230 31891365
            32441565 34091603 34951620 36731639 37661562
           


Last Updated: 405 PM EDT FRI SEP 08 2017