MESOSCALE PRECIPITATION DISCUSSION 0758...CORRECTED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1204 AM EDT SUN OCT 30 2016
 
CORRECTED FOR TYPO

AREAS AFFECTED...NORTHWEST CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 300357Z - 301557Z
 
SUMMARY...AN INCOMING COLD FRONT IS EXPECTED TO ELEVATE RAIN RATES
ABOVE 0.5" FROM ~10Z ONWARD AS INSTABILITY FROM THE PARENT DEEP
LAYERED CYCLONE MOVES INTO THE REGION.

DISCUSSION...A DEEP-LAYERED LOW NEAR 38.5N 132.5W IS ACCOMPANIED
BY DECENT INSTABILITY AS SEEN ON INFRARED IMAGERY WITH SHOWERY
EMBEDDED CLOUD ELEMENTS WITH CLOUD TOPS NEAR -40C.  THE LIGHTNING
DISPLAY NETWORK ADVERTISES EMBEDDED THUNDERSTORMS WEST OF THE
127TH MERIDIAN NEAR SOME OF THE COLDER CLOUD TOPS.  MUCAPES OF 100
J/KG LIE JUST OFFSHORE THE NORTHERN CA COAST PER SPC MESOANALYSES.
 ALOFT, WHILE NAM MASS FIELDS INDICATE A MERGER OF THE SUBTROPICAL
JET WITH THE SOUTHERN STREAM OF THE WESTERLIES, SATELLITE IMAGERY
APPEARS TO SHOW SOME SEPARATION BETWEEN THE TWO STREAMS ACROSS
NORTHWEST CA, WHERE DIVERGENCE ALOFT IS INCREASING PER A RECENT
SAB/NESDIS BRIEFING.  INFLOW AT 850/700 HPA IS 15/30 KTS
RESPECTIVELY BASED ON VAD WIND PROFILES.  PRECIPITABLE WATER
VALUES OF NEAR 1" ARE SEEN HERE PER GPS INFORMATION.  AT THE
SURFACE, A SEGMENT OF THE POLAR FRONT IS WEAKENING NEAR THE
SACRAMENTO VALLEY WHILE A SECONDARY FRONT APPEARS TO BE FORMING
NEAR 127 WEST LONGITUDE.

RAP GUIDANCE ALONG WITH SATELLITE TRENDS SUGGEST THAT BOUNDARY
LAYER MOISTURE CONVERGENCE ALONG WITH INSTABILITY, IN THE FORM OF
500+ J/KG MUCAPES, SHOULD APPROACH THE COAST OF NORTHWEST CA FROM
~10Z ONWARD.  INFLOW AT 850/700 HPA IS EXPECTED TO RISE TO 35/50
KTS RESPECTIVELY SUNDAY MORNING.  THERE IS A GOOD SIGNAL IN THE
MESOSCALE GUIDANCE FOR LOCAL AMOUNTS OF 3" THROUGH 16Z, WITH
HOURLY RAIN TOTALS BREACHING 0.5" FROM ~10Z ONWARD. IN AREAS WITH
BURN SCARS AND WITHIN SENSITIVE RIVER BASINS, THE EXPECTED RAIN
RATES COULD CAUSE ISSUES. 

ROTH

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

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

LAT...LON   41422153 40242132 39062209 37962266 38172343 
            39352397 40102449 40662410 41342283