MESOSCALE PRECIPITATION DISCUSSION 0010
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
942 AM EST SUN JAN 08 2017
 
AREAS AFFECTED...CENTRAL CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 081442Z - 081942Z
 
SUMMARY...INCREASING RAIN RATES WITHIN WARM SECTOR BEFORE COLD
FRONT STARTS SHIFTING THROUGH BY 18-20Z.

DISCUSSION...89GHZ MOSAIC FROM AMSU/SSMIS MICROWAVE SENSORS
DENOTED A WNW TO ESE BAND OF ENHANCED CONVECTION LIFTING NORTH
ACROSS CENTRAL CALIFORNIA THIS MORNING AND LOCAL RADAR MOSAIC
ALONG WITH RAPID SCAN GOES-W IR/WV LOOP SUPPORTS THIS FROM STS TO
MHR CONCURRENT WITH ENHANCED DEEPER CONVECTIVE SHOWERS.  THIS HAS
SUPPORTED INCREASED RATES SEEN IN NWS MESONET OBSERVATIONS AROUND
.5"/HR WITH SOME ISOLATED VALUES UP TO .9" IN SW FACING OROGRAPHY
IN SONOMA COUNTY.  RADAR ALSO INDICATES ENHANCING
SHOWERS/CONVECTIVE ELEMENTS ALONG A PRE-FRONTAL BOUNDARY THAT
EXTENDS SW FROM MARIN/SONOMA COUNTY. HI-RES WRF-ARW SEEMS TO HAVE
THE BEST REPRESENTATION OF THE CURRENT SETUP THOUGH IS A BIT TOO
FAR WEST WITH THIS PRE-FRONTAL BAND. THIS WILL LEAVE THE FOCUS OF
PERSISTENT/TRAINING SHOWERS OVER MARIN/SONOMA COUNTIES (2-3"
POSSIBLE) CONTINUING INTO THE VALLEY ALONG THE YOLO/SUTTER/YUBA
LINE THOUGH WITH REDUCED RATES (TOTALS 1-2") GIVEN THE LOWEST
LEVELS WERE SCOURED BY THE COASTAL OROGRAPHY REDUCING RAINFALL
EFFICIENCY.  

WV/IR LOOP INDICATES A WEAK SPEED MAX/SHORTWAVE RIDGING LIFTING
NORTH CURRENTLY THROUGH N CA...SUPPORTING INCREASED DIVERGENCE
ALOFT AND COOLING TOPS ALONG THE COAST.  THIS IS SIMILAR
ENHANCEMENT THAT CAN BE SEEN FURTHER SW ALONG THE SUBTROPICAL
MOISTURE STREAM THAT SUGGESTS CONTINUED OR EVEN SLIGHTLY INCREASED
SHOWERS THAT WILL ADVANCE NORTHWARD TOWARD THE MOUTH OF THE SAN
FRAN BAY AREA TIMED AROUND THE 1530-1600 TIME FRAME.  ARW/HRRR
SUGGESTS INCREASED INSTABILITY VALUES EXCEEDING 250 J/KG
CONCURRENT WITH THE NARROW 1.5" TPW PLUME ADVECTED ON 50+ KTS OF
SWLY 850MB FLOW... LIKELY TO AFFECT THE SANTA CRUZ RANGE THAT WAS
ALREADY AFFECTED THIS MORNING WITH 2-4" TOTALS...CONTINUING TO
POSE ADDITIONAL FLASH FLOODING THREAT THERE AS WELL WITH AN
ADDITIONAL 1-2" EXPECTED THROUGH 20Z. 

ACROSS THE SACRAMENTO VALLEY INTO THE NORTHERN SIERRAS...THE WARM
FRONT WILL CONTINUE TO LIFT NORTHWARD OVER THE NEXT FEW HOURS
LEADING TO SLIGHTLY VEERED LOWER LEVEL FLOW SUPPORTING NEARLY
ORTHOGONAL MST TRANSPORT.  TPWS LIKELY OVER 1.0" WITHIN THE
850-700MB LAYER ON INCREASING FLOW FROM 45KTS TO 60+KTS SUPPORTS
STRONG OROGRAPHIC ASCENT WITH RAIN RATES EXCEEDING .5"/HR.  THE
STRONG WAA WILL CONTINUE TO SUPPORT RISING FREEZING LEVELS OVER
10000 FT SUPPORT RAINFALL TOTALS OF 2.5-3.5" CENTERED ON
BUTTE/PLUMAS INTO SIERRA AND NEVADA COUNTIES.    

GALLINA

ATTN...WFO...EKA...HNX...MTR...REV...STO...

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

LAT...LON   40512140 40012073 39392038 38872018 38601962 
            38121924 37741897 37601923 37952001 38202050 
            38222105 37862124 37232153 37042169 36922181 
            37042225 37382249 37792277 38332313 38652359 
            39012364 39432343 39642267 39422207 40202187