MESOSCALE PRECIPITATION DISCUSSION 0759
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
909 AM EDT SUN OCT 30 2016
 
AREAS AFFECTED...NORTHERN CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 301330Z - 310000Z
 
SUMMARY...BAND OF HVY RAIN COMING ASHORE IN N CA RATES OVER .5"/HR
LIKELY WITH PSBL ISOLATED 1HR TOTALS NEAR 1" IN OROGRAPHICS
POTENTIALLY LEADING TO SOME LOCALIZED FLOODING CONCERNS.  

DISCUSSION...GOES-W WV LOOP CONTINUES TO SHOW THE ADVANCEMENT OF
LARGE COLD UPPER LOW CENTERED JUST SOUTHWEST OF 40N130W BENCHMARK
WITH WELL DEFINED SHORTWAVE FURTHER SOUTH ALONG THE BASE OF THE
TROF.  THIS SHORTWAVE CONTINUES TO ENHANCE AS WELL AS LEAD TO
NEGATIVE TILTING OF THE TROF OVERALL.  THIS SUPPORTS AN
INCREASINGLY DIFFLUENT UPPER LEVEL PATTERN WITH EXCELLENT
EVACUATION INTO 130KT 250MB POLAR JET ACROSS S OR ATTM.  THIS
SUPPORTS STEEPENING MID-LEVEL LAPSE RATES INCREASING INSTABILITY
NEAR THE COAST.  RAP MUCAPES OF 100-500 J/KG WILL REMAIN OFFSHORE
AND THOUGH LIGHTNING DETECTION IS LIMITED...GOES-IR AND KBHX RADAR
SHOWS INCREASING VERTICAL GROWTH WITH EXPANDING STRATO-CU NEAR
ALONG THE NORTHWEST CA COAST LINE.  TPWS UP TO 1.0" AVAILABLE
ALONG STRONG SOUTHERLY FLOW WITH CURRENT DYNAMIC SETUP SHOULD
SUPPORT RAIN RATES OF .5-.75"/HR FOR THESE COASTAL SHOWERS
ENHANCED SLIGHTLY BY OROGRAPHIC ASCENT ALONG SOUTHWARD FACING
SLOPES.   

AS THE MOISTURE PLUME/DIFFLUENT UPPER PATTERN SHIFTS
ASHORE...STRONG 850-7H MST SOUTHERLY FLOW...25KT/45KT PER BBX VAD
PROFILE INCREASING TO 40KT/50KT...THROUGH THE SACRAMENTO VALLEY
WILL IMPACT THE TRINITY MOUNTAINS PROVIDING VERY STRONG OROGRAPHIC
ASCENT SUPPORTING THE POSSIBILITY OF RATES NEAR 1" IN AN HOUR AND
CLOSE TO 2-2.5"/3HRS.  THIS IS VERY NEAR FFG VALUES IN THIS
REGION...SO THERE MAY BE A NARROW WINDOW FOR FF TO OCCUR BETWEEN
17-19Z BEFORE WARM CONVEYOR BELT FOCUSES ACROSS THE LASSEN PEAK
REGION SLIPPING QUICKLY SOUTHWARD ALONG THE SIERRA RANGE.  

HI-RES GUIDANCE IS SUGGESTIVE AS THE SOUTHERLY FLOW VEERS MORE
TOWARD SOUTHWEST...ISOLATED CONVECTIVE ELEMENTS MAY HANG UP UNDER
STRONG OROGRAPHIC FORCING PROVIDING ANOTHER LOCATION FOR 1-2" TO
FALL IN A 2-3HR WINDOW.  THOUGH WITH CAA ALOFT...LOWERING SNOW
LEVELS SHOULD KEEP GREATEST RAINFALL BELOW 7K FT THROUGH 21-00Z
FROM S PLUMAS COUNTY TO TUOLUMNE COUNTY.  

GALLINA

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

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

LAT...LON   42322435 41952296 41612147 40982093 40382058 
            39322051 38812002 37901933 37461997 37942060 
            38702109 39302194 38812258 38412314 39032383 
            39662406 40222443 40612457 41272424