MESOSCALE PRECIPITATION DISCUSSION 0011
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EST SUN JAN 08 2017
 
AREAS AFFECTED...CENTRAL CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 081900Z - 090300Z
 
SUMMARY...HEIGHT FALLS FROM DEEPER POLAR LOW AND EXITING SHORTWAVE
WILL SUPPORT A SOUTH AND EASTWARD SHIFT AND NARROWING OF THE
SUBTROPICAL MOISTURE PLUME THROUGH THE AFTERNOON HOURS. FLASH
FLOODING REMAINS POSSIBLE GIVEN ANTECEDENT CONDITIONS PARTICULARLY
IN BURN SCARS. 

DISCUSSION...BROADER SCALE GOES-W WV SHOWS THE LAST REMAINING FORM
OF THE SHEARED UPPER LOW THAT WAS OUT NEAR 145W YESTERDAY IS
LOCATED JUST NW OF THE 30N130W BENCHMARK WITH INCREASING
NORTHWESTERLY FLOW/HEIGHT FALLS BEGINNING TO DESCEND FROM THE
ENERGY AROUND THE MAIN UPPER LOW NORTH OF 40N.  THIS HAS LEAD TO
INCREASED CONFLUENCE OF THE MID TO UPPER LEVEL FLOW OFFSHORE OF
CENTRAL CALIFORNIA AND SW MAKING DETECTION OF INCREASED
DPVA/FORCING PACKETS LESS DISCERNIBLE.  YET DUE TO THE REMAINDER
OF THE SHEARED WAVE...ONE CAN BE TRACKED SUPPORTING A LOCALIZED
INCREASE IN DEEPER CONVECTION NEAR 36N124W WHICH BASED ON LINEAR
EXTRAPOLATION SHOULD REACH THE SANTA CRUZ RANGE ABOUT 19-20Z.  
NORTHEAST OF THIS WAVE...THERE SHOULD REMAIN GENERAL UPPER LEVEL
DIFFLUENCE TO KEEP THE SWLY LOW LEVEL MOISTURE PLUME A BIT BROADER
ALLOWING FOR INCREASED DURATION OF MODERATE TO HEAVY RAINFALL FOR
THE CENTRAL VALLEY INTO THE NORTHERN AND CENTRAL SIERRAS.  OPPOSED
TO SOUTH AND WEST OF THE INFLECTION THE SWLY WILL CONTINUE TO BE
VERY MOIST WITH STRONG FLUX AHEAD OF THE FRONT BUT WILL BE A BIT
NARROWER...SO INCREASED RATES ALONG THE COASTAL FRONT BUT SHORTER
DURATION AS THE MOISTURE AXIS SLIDES SOUTH AND SHIFTS FROM SSW-NNE
ORIENTATION TO MORE SW TO NE TRACKING ALONG THE SANTA LUCIA RANGE
TOWARD 22-00Z.

COASTAL RANGES...
BLENDED TPW AND RR INDICATE VALUES ARE STEADILY INCREASING TOWARD
1.5" AS THE PLUME OF MOISTURE NARROWS WITH .5"/HR RATES DETECTED
(THOUGH LOCALLY HIGHER GIVEN LARGE FOOTPRINT FLATTENS THE VALUE
DUE TO AVERAGING).  THOUGH AS THE SHORTWAVE CONTINUES TO LIFT INTO
OR/WA AND FURTHER AWAY...LOW LEVEL FLOW WILL SLACKEN AS WELL FROM
50KTS TO 35-40 KTS AT 850MB TOWARD 00Z REDUCING SOME ENHANCEMENT
OF RATES OVER .5"/HR IN SW FACING OROGRAPHY IN MONTEREY/SAN LUIS
OBISPO AND EVENTUALLY SANTA BARBARA COUNTY.  FLASH FLOODING/DEBRIS
FLOWS SHOULD REMAIN A THREAT ALONG THIS REGION ESPECIALLY IN BURN
SCARS.  THIS SCENARIO IS SUPPORTED BY MUCH OF THE HI-RES GUIDANCE
BUT CURRENTLY FAVORING THE TIMING OF THE RECENT ESRL EXP. HRRR AND
WRF-ARW...THIS WOULD ACCOUNT FOR 2.5-3.5" FOR THE SANTA CRUZ RANGE
AND NORTHERN SANTA LUCIA THROUGH 03Z.

CENTRAL VALLEY/SIERRA NEVADA RANGE...
BROAD MID-LEVEL/UPPER LEVEL ASCENT FROM DIFFLUENCE FROM EXITING
SHORTWAVE TROF AND ASSOCIATED 130 KT JET FURTHER NORTH WILL
SUPPORT A BROADER PLUME OF CONTINUING SHOWERS ACROSS THE CENTRAL
VALLEY WITH UP TO AN ADDITIONAL .75-1.0" ACROSS SACRAMENTO/W EL
DORADO AND N SAN JOAQUIN COUNTIES.  STRONGER ASCENT DUE TO THE
SLOPES OF THE SIERRAS WILL CONTINUE SUPPORTING RATES UP TO .5"/HR
THROUGH 00Z WITH THE POTENTIAL OF AN ADDITIONAL 4-6" FROM BUTTE TO
E EL DORADO COUNTY.  TOTALS OF 3-5" ARE EXPECTED FURTHER SOUTH
ALONG THE SOUTHERN SIERRAS DUE TO PERSISTENT SWLY ASCENT PRIOR TO
THE MAIN MOISTURE AXIS SLIDING SEWARD ALONG IT WITH RATES OF
.1-.25"/HR PRIOR TO THE PLUME AND .5-.75"/HR DURING THE NARROW
PLUME OF INCREASED TPWS MARCHES STARTING AROUND 22Z IN ALPINE
COUNTY REACHING MADERA COUNTY ABOUT 01-02Z. 

GALLINA

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

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

LAT...LON   40162135 39772065 39142009 38461953 37901895 
            37221843 36741816 36371805 36341851 36621886 
            36951961 37221996 37802027 37612077 37052093 
            36642060 36182027 35682015 35332011 34962029 
            34772050 35062079 35372106 35932164 36512208 
            36882224 37492257 37962224 38912176 39602170 
            39872158