MESOSCALE PRECIPITATION DISCUSSION 0044
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1026 PM EST SAT MAR 05 2016
 
AREAS AFFECTED...CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 060325Z - 060900Z
 
SUMMARY...STRONG ATMOSPHERIC RIVER CONDITIONS WILL CONTINUE ACROSS
CENTRAL AND NORTHERN CA OVERNIGHT WITH AN INCREASING FOCUS OF
HEAVY RAINFALL OVER THE COASTAL RANGES AND INTERIOR FOOTHILLS OF
THE SIERRA-NEVADA.

DISCUSSION...GOES-15 WV IMAGERY SHOWS A STRONG SHORTWAVE TROUGH
AMPLIFYING OFF THE WEST COAST WITH A SIGNIFICANT AMOUNT OF
VORT/JET ENERGY DIGGING INTO THE BASE OF THE TROUGH OFFSHORE
CENTRAL CA. STRONG DEEP LAYER ASCENT AHEAD OF THE TROUGH CONTINUES
TO INTERACT WITH A PLUME OF PWATS REACHING 1 TO 1.2 INCHES AS PER
BLENDED TPW IMAGERY JUST OFFSHORE CA...ALONG WITH AT LEAST A VERY
MODEST LEVEL OF INSTABILITY WHICH AS PER RAP ANALYSES IS REACHING
AS HIGH AS 250 J/KG JUST ALONG AN APPROACHING COLD FRONT.

STRONG ATMOSPHERIC RIVER CONDITIONS WILL CONTINUE OVERNIGHT AS
STRONG MOISTURE TRANSPORT IN THE 850/700 MB LAYER FOCUSES INTO THE
COASTAL RANGES AND ESPECIALLY THE FOOTHILLS OF THE CENTRAL AND
NORTHERN SIERRA-NEVADA. THE GFS INDICATES 850/700 MB MOISTURE FLUX
ANOMALIES EXCEEDING 5 STANDARD DEVIATIONS ABOVE NORMAL OVER THE
NEXT SEVERAL HOURS OVER CENTRAL CA...WITH THE MEAN FLOW AIMED
NEARLY ORTHOGONAL TO THE HIGHER TERRAIN. GIVEN THE COMBINATION OF
STRONG OROGRAPHIC FORCING AND DEEP LAYER ASCENT FOSTERED BY THE
ARRIVAL OF A ROBUST 250 MB JET COUPLET...RAINFALL RATES SHOULD BE
QUITE HEAVY...AND THE BLENDED RAIN RATE PRODUCT HAS BEEN SHOWING
0.50 TO 0.60 INCH/HR RATES JUST OFFSHORE. THESE HEAVIER RATES WILL
MOVE INLAND.

THE HIRES GUIDANCE INDICATES THE COLD FRONT WILL MOVE INLAND OVER
THE NEXT FEW HOURS AND BEGIN TO SETTLE SOUTHEAST AS THE UPPER
TROUGH ADVANCES EAST. EXPECT ADDITIONAL RAINFALL AMOUNTS THROUGH
09Z OF AS MUCH AS 2 TO 4 INCHES FOR THE IMMEDIATE COASTAL
RANGES...ESPECIALLY SOUTH OF SAN FRANCISCO INCLUDING THE SANTA
CRUZ RANGE AND THE SIERRA DE SALINAS WHERE AMSU DATA INDICATES
HEAVIER RATES OFFSHORE WILL BE IMPACTING THESE AREAS. LIKEWISE IN
THE FOOTHILLS OF THE CENTRAL AND NORTHERN SIERRA-NEVADA
RANGE...EXPECT 2 TO 4 INCHES OF RAIN BELOW THE SNOW LINE. EXPECT
THESE RAINS TO FOSTER SOME POTENTIAL FOR RUNOFF PROBLEMS. WILL
CONTINUE TO MONITOR.

ORRISON

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

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

LAT...LON   41752393 41662221 40102111 38902009 37761901 
            36221832 34881840 34141917 34182001 34642079 
            35592139 36952238 38842371 40662447