MESOSCALE PRECIPITATION DISCUSSION 0609
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
152 AM EDT SAT AUG 27 2016
 
AREAS AFFECTED...FAR EASTERN CA...SOUTHERN NV...NORTHWEST
AZ...SOUTHWEST UT 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 270545Z - 271000Z
 
SUMMARY...SCATTERED CLUSTERS OF THUNDERSTORMS WITH INTENSE
RAINFALL RATES MAY EXPAND A BIT MORE IN COVERAGE OVER THE NEXT
COUPLE OF HOURS.

DISCUSSION...A WELL-DEFINED SHORTWAVE TROUGH IS SEEN IN WV IMAGERY
DIGGING SOUTHEAST ACROSS CENTRAL CA AND FAR WESTERN NV WHICH IS
FOSTERING AN INCREASINGLY DIVERGENT FLOW PATTERN ALOFT ACROSS FAR
EASTERN CA...SOUTHERN NV AND NORTHWEST AZ. THIS INCREASED LARGE
SCALE ASCENT JUXTAPOSED WITH A POOL OF MODEST INSTABILITY OVER THE
REGION WITH MUCAPE VALUES OF UP TO 1000 J/KG...IS HELPING TO
GENERATE SCATTERED SMALL CLUSTERS OF THUNDERSTORMS.

CLOUD TOPS OVER THE LAST HOUR HAVE CONTINUED TO COOL WHICH
SUGGESTS STRONGER FORCING WITH THE SHORTWAVE...AND IT WOULD APPEAR
THAT CONVECTION WILL ATTEMPT TO BECOME SOMEWHAT BETTER ORGANIZED
AND EXPANSIVE IN COVERAGE OVER THE NEXT COUPLE OF HOURS AS FURTHER
SHORTWAVE AMPLIFICATION OCCURS AND IN CONJUNCTION WITH A
PERSISTENT POOL OF FAVORABLE MOISTURE AND INSTABILITY.

RECENT RUNS OF THE NCEP HRRR AND THE ESRL HRRR DO NOT HAVE A GOOD
HANDLE ON THE CURRENT ACTIVITY...BUT DO SUPPORT THE IDEA OF MORE
ORGANIZED HEAVY RAINFALL DEVELOPING AND FOCUSING OVER NORTHWEST AZ
LATER IN THE NIGHT TOWARD DAWN AND THEN AFTER DAWN WHICH HAS THE
SUPPORT FROM THE 00Z ARW AND 00Z NMMB.

PWATS OVER FAR SOUTHERN NV AND EASTERN CA ARE AS HIGH AS 1.25
INCHES...AND WHILE THERE ARE SOME CONCERNS OF MID LEVEL DRY AIR
INTRUSION...THE RAINFALL RATES ARE STILL EXPECTED TO BE LOCALLY
HEAVY AND MAY EXCEED 1 INCH/HR. LOCALIZED STORM TOTALS OF UP TO 2
INCHES ARE POSSIBLE OVERNIGHT. THIS WOULD FOSTER SOME POTENTIAL
FOR FLASH FLOODING.

ORRISON

ATTN...WFO...FGZ...PSR...SLC...VEF...

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

LAT...LON   37751317 37641262 37151193 36331187 35181289 
            34361325 34041379 34201482 34681563 35151600 
            35791591 36361495 37401407