MESOSCALE PRECIPITATION DISCUSSION 0041
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
930 AM EST SAT MAR 05 2016
 
AREAS AFFECTED...NW CALIFORNIA...SW OREGON 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 051500Z - 060300Z
 
SUMMARY...LEADING WARM FRONT SHOWERS TO REACH AREA BY 17Z WITH
CONTINUED MODERATE RAINS UNTIL COLD FRONTAL ZONE PUSHES THROUGH
AROUND 00-03Z.  

DISCUSSION...TRADITIONAL GOES SATL IMAGERY ALONG WITH AMSU 89GHZ
MOSAIC DENOTE A PHASING LINE OF SHORTWAVE VORTICITY CENTERS ALONG
A NW TO SE AXIS FROM 43N139W TO 39N135W WITHIN THE POLAR SIDE OF
THE SYSTEM WITH EMBEDDED ENHANCING BAROCLINIC LEAF STRUCTURES IN
THE SUBTROPICAL STREAM NEAR 130W AND 135W.  THE AMSU 89GHZ SHOWS
THE LOW LEVEL STRUCTURE BEGINNING TO AMPLIFY AS WELL BETWEEN THESE
UPPER LEVEL STRUCTURES UNDER THE BROAD SCALE DPVA AND DIFFLUENCE
IN THE SPLIT POLAR/SUBTROPICAL JET STRUCTURE.  IN THE MOISTURE
STREAM THERE IS A SLIGHT SPLIT/DUAL MAXIMA STRUCTURE DUE TO A WEAK
SHORTWAVE/SURFACE REFLECTION IN THE SUBTROPICAL STREAM SOUTH OF
30N NEAR 130W... STILL BOTH ARE POTENT WITH 1.25-1.5" VALUES
OBVIOUSLY MAXIMIZED NEARER THE SURFACE LOW REFLECTION AND HIGHEST
MST CONVERGENCE...COINCIDENT WITH THE LEAF STRUCTURES AS WELL. 
BLENDED RAIN RATE AND SPECIFIC AMSU RR PASSES INDICATE RATES OF UP
TO .3"/HR...NEARER TO THE THE SURFACE LOW DEEPEST/CONVECTION AHEAD
OF THE S/W NEAR 135W.  THOUGH BROADER .1-.2"/HR RATES EXIST ALONG
THE FRONTAL BOUNDARY.  

TIMING OF THE LEAD BAROCLINIC LEAF AND NORTHWARD RETURNING WARM
FRONT WILL BEGIN TO AFFECT NW CALIFORNIA AROUND 16-17Z WITH RATES
INCREASING TO .25-.4"/HR IN SW FACING OROGRAPHY MAINLY NORTH OF
39N FOR A FEW HOURS.  AFTERWARD...A WEAK LULL IN INTENSITY WILL
OCCUR IN THE 21-23Z TIME PERIOD UNTIL THE STRENGTHENING COLD
FRONTAL ZONE/CONVECTION APPROACHES WITH UP TO .5-.75"/HR FOR A FEW
HOURS POSSIBLY UP TO 1"/HR WITH SOME DEEPER CONVECTION FED BY SOME
POTENTIAL WEAK INSTABILITY UP TO 100-250 J/KG PRE-COLD FRONT
COMPOUNDED BY THE OROGRAPHIC ASCENT.  EXPECTATION IS FOR 3-4"
TOTALS ARE LIKELY IN BEST OROGRAPHY THOUGH 5-6" TOTALS ARE NOT OUT
OF THE REALM OF POSSIBILITY THROUGH THE NEXT 12HRS...WHICH SEEMS
TO BE WELL HANDLED BY MUCH OF THE HI-RES GUIDANCE ESPECIALLY THE
RECENT FEW RUNS OF THE HRRR AND THE 00Z ARW.

GALLINA

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

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

LAT...LON   42772375 41832190 40922109 39532153 38142250 
            38082310 39012439 41152497 42482482