MESOSCALE PRECIPITATION DISCUSSION 0755
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
606 PM EDT THU OCT 27 2016
 
AREAS AFFECTED...CNTRL CA COASTAL RANGES 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 272205Z - 280705Z
 
SUMMARY...HEAVY RAIN WILL BEGIN TO INCREASE ACROSS THE CNTRL
COASTAL RANGES OF CA AFTER 00Z WITH RAINFALL RATES PEAKING ABOVE
0.75 IN/HR WHICH MAY LEAD TO LOCALIZED FLASH FLOODING ACROSS BURN
SCAR REGIONS. FARTHER INLAND...RAIN RATES NEAR 0.5 IN/HR ARE
EXPECTED INTO THE SIERRA NEVADA RANGE.

DISCUSSION...21Z WATER VAPOR/INFRARED IMAGERY SHOWED A POTENT
CLOSED LOW CENTERED NEAR 31N 129W...WITH A NEAR NEUTRALLY ORIENTED
TROUGH AXIS EXTENDING OUTWARD FROM THE CENTER. A BAROCLINIC LEAF
HAS BECOME MORE PREVALENT OVER THE PAST SEVERAL HOURS JUST AHEAD
OF THE UPPER LOW AND SURFACE LOW ANALYZED NEAR 31N 127W AT 21Z.
THIS AREA OF COLDER CLOUD TOPS IS COINCIDENT WITH 850-700 MB
CONVERGENCE AND EXPANDING UPPER LEVEL DIFFLUENCE.

KMUX AND KVBX RADARS HAVE SHOWN AN AXIS OF SHOWER ACTIVITY MOVING
ASHORE ACROSS SRN MONTEREY COUNTY OVER THE PAST 1-2 HOURS WITH
ECHOES PEAKING IN THE 40+ DBZ RANGE...BUT LIKELY EXPERIENCING
BRIGHT BANDING GIVEN THEIR DISTANCE FROM THE RDA. LOCAL
OBSERVATIONS...THOUGH SPARSE...HAVE BEEN LESS THAN 0.15 IN/HR IN
THE COASTAL RANGES. THE RIGHT ENTRANCE REGION OF A SW TO NE
ORIENTED UPPER LEVEL JET OF 115 KTS CONFIRMED VIA EARLIER GOES HD
WIND PRODUCT IS LIKELY AIDING IN UPPER LEVEL DIVERGENCE. 

AS THE UPPER TROUGH CONTINUES TOWARD THE CNTRL CA COAST
TONIGHT...SHORT TERM MODELS ARE UNANIMOUS IN IT ACQUIRING A
NEGATIVE TILT WHICH WILL ENHANCE UPPER DIFFLUENCE WHILE ALSO
HINTING AT UPPER LEVEL JET COUPLING ALONG THE COAST BETWEEN MRY
AND SBP. RAP MODEL FORECASTS ALSO SHOW 700 MB CONFLUENCE FOCUSING
ACROSS SRN MONTEREY/NRN SAN LUIS OBISPO COUNTIES AFTER 00Z...WITH
30-40 KTS FROM THE SOUTH ALONG AND EAST OF POINT CONCEPTION. 

PRECIPITABLE WATER VALUES WERE OBSERVED BETWEEN 1.25 AND 1.50
INCHES NEAR MONTEREY BAY WITH HIGHER VALUES OFFSHORE. SOME OF THIS
MOISTURE IS TIED TO THE MID-UPPER LEVEL MOISTURE BEING DRAWN NORTH
FROM TROPICAL STORM SEYMOUR. AS THE UPPER TROUGH AXIS APPROACHES
THE COAST TONIGHT...1.6 TO 1.7 INCH VALUES WILL BE POSSIBLE ALONG
THE COAST JUST NORTH OF POINT CONCEPTION WITH +4 TO +5
STANDARDIZED ANOMALIES EXTENDING WELL INLAND ACROSS THE SIERRA
NEVADA. THESE VALUES COMBINED WITH WEAK INSTABILITY...BELOW 250
J/KG WILL LEAD TO CONVECTIVE ELEMENTS WITH RAIN RATES OF 0.75+
IN/HR ALONG THE COASTAL RANGES WITH RATES CLOSER TO 0.5 IN/HR INTO
THE UPSLOPE REGIOSN OF THE SIERRA NEVADA. RAINFALL TOTALS OF 2-3
INCHES WILL BE POSSIBLE ACROSS BOTH REGIONS THROUGH 09Z.

OTTO

ATTN...WFO...HNX...LOX...MTR...REV...STO...

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

LAT...LON   39922062 39172039 38392004 38321990 37311894 
            36811903 36311969 35031988 34392039 34622104 
            35462135 36312199 36712187 37452184 38202124 
            39222147 39822118