MESOSCALE PRECIPITATION DISCUSSION 0672
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
202 PM EST WED DEC 09 2015
 
AREAS AFFECTED...SW OREGON/N. CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 091901Z - 100701Z
 
SUMMARY...THE NEXT SURGE OF HEAVY RAINFALL WILL REACH N.
CALIFORNIA AND SW. OREGON 03-06Z AND LAST FOR 6 HOURS...WITH 3
INCHES OF RAIN POSSIBLE.

DISCUSSION...THE FRONTAL BOUNDARY OVER N. CALIFORNIA HAS NEARLY
STALLED WITH A DEEP PW PLUME NEAR 1 INCH RUNNING SOUTHWEST AND
PARALLEL TO THE BOUNDARY. MEANWHILE...WATER VAPOR AND INFRARED
IMAGERY SHOW A POWERFUL CYCLONE NEAR 45N/145W WITH MODEST
LIGHTENING DENSITY ALONG A TRAILING COLD FRONT AND A RECENT AMSU
PASS SHOWING 6-HOURLY RAIN RATES NEAR 0.75 WHICH IS HIGH FOR A
COARSELY-GRIDDED VALUE. 

OTHER THAN THE 12Z GEM REGIONAL AND TO A LESSER EXTENT THE 00Z
ECMWF...MODELS INCLUDING HI-RES SOLUTIONS...ALLOW THE CYCLONE TO
CONTINUE APPROACHING THE STALLED FRONT TOWARD 00Z...WITH THE
STALLED FRONT ACROSS N. CA THEN SURGING NORTHWARD WITH 850-700 MB
MOISTURE FLUX ANOMALIES OF 3 TO 4 STANDARD DEVIATIONS ABOVE NORMAL
ACCOMPANYING THE WARM FRONTAL AND COLD FRONTAL PASSAGES. 

BASED ON A MODEL CONSENSUS OF THE HI-RES SOLUTIONS...850 TO 700 MB
LAYER WINDS OF 60 TO 80 KNOTS...PW VALUES OF 1 TO 1.25
INCHES...AND ACCOUNTING FOR WEAK CONVECTIVE INSTABILITY AND
OROGRAPHICS...HOURLY RAIN RATES OF 0.5 INCHES ARE LIKELY AND
SHOULD LAST FOR UPWARDS OF 6 HOURS...WITH AN ARRIVAL TIME OF
03-06Z. BASED ON THESE NUMBERS...TOTAL RAINFALL AMOUNTS MAY REACH
3 INCHES FROM THE SHASTAS AND SISKIYOUS...NORTHWARD INTO THE S.
OREGON CASCADES OVERNIGHT.

JAMES

ATTN...WFO...EKA...MFR...PQR...REV...STO...

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

LAT...LON   43592217 41992206 40102071 39732145 41002186 
            40672288 39732314 39292342 39542427 41002505 
            42352502 43472402