MESOSCALE PRECIPITATION DISCUSSION 0332
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT WED JUL 08 2015
 
AREAS AFFECTED...INTERIOR NORTHERN CA/NORTHWESTERN NV/SOUTHERN
OR... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 081900Z - 090000Z
 
SUMMARY...AS DIURNAL HEATING HAS COMMENCED...CONVECTION BEGINNING
TO PERCOLATE OVER THE SIERRA NEVADA RANGE. GIVEN A FAVORABLE UPPER
DIVERGENCE PATTERN OVER THE REGION...EXPECT WELL ORGANIZED STORMS
CAPABLE OF PRODUCING FLASH FLOODING...PARTICULARLY IN AREAS OF
COMPLEX TERRAIN.

DISCUSSION...A MID/UPPER LOW IS CURRENTLY CROSSING THE SAN
FRANCISCO/OAKLAND BAY AREA WITH STRONG ASCENT OCCURRING TO ITS
NORTH AND EAST. CB TOWERS ARE ALREADY EVIDENT ON THE VISIBLE
SATELLITE IMAGERY ACROSS THE SIERRA. TO THE NORTH...A REGION OF
AGITATED CU WAS NOTED WHICH SHOULD CONTINUE TO DEVELOP BEING IN
THE REGION OF ENHANCED UPPER DIVERGENCE. GIVEN THE ANOMALOUS PWATS
IN PLACE...ROUGHLY 1 TO 1.25 INCHES PER GPS SOUNDER DATA...EXPECT
INDIVIDUAL CELLS TO PRODUCE HEFTY RAINFALL RATES. GIVEN THE REGION
SAW HEAVY PRECIPITATION YESTERDAY...THE REGION MAY BE MORE
SUSCEPTIBLE TO FLASH FLOODING ISSUES THIS AFTERNOON/EVENING.
ADDITIONALLY...WEAK STEERING FLOWS SHOULD ALLOW THUNDERSTORMS TO
PRODUCE HEAVY AMOUNTS OF RAIN OVER A FOCUSED AREA. AND GIVEN
COMPLEX TERRAIN IS IN THE EQUATION...THESE AREAS SHOULD BE MOST
PRONE TO FLASH FLOOD ISSUES.

WHILE VARIABLE IN NATURE...THE CONVECTION-ALLOWING MODELS SHOW A
DECENT SIGNAL FOR HEAVY RAINFALL THROUGH AT LEAST 00Z. SUCH MODELS
SUPPORT THE BEST ACTIVITY OVER THE SIERRA/SHASTA RANGES AS IS
SUPPORTED BY WHERE THE CURRENT CONVECTION IS CONGREGATING.


RUBIN-OSTER

ATTN...WFO...BOI...HNX...LKN...MFR...REV...STO...VEF...

ATTN...RFC...CNRFC...NWRFC...

LAT...LON   42141902 41461804 40681869 39791929 38991926 
            38231874 36701802 36471852 37031944 38362052 
            39192131 40192236 41192243 42102107