MESOSCALE PRECIPITATION DISCUSSION 0756
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
208 AM EDT FRI OCT 28 2016
 
AREAS AFFECTED...TERRAIN OF CENTRAL CA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 280607Z - 281807Z
 
SUMMARY...THE COMBINATION OF AN UPPER TROUGH WITH MOISTURE
STREAMING NORTH FROM WEAKENING TROPICAL CYCLONE SEYMOUR COULD LEAD
TO HOURLY RAIN RATES OF 0.5", PARTICULARLY AFTER 12Z.

DISCUSSION...A NEGATIVELY TILTED UPPER TROUGH IS APPROACHING THE
GOLDEN STATE AT THIS TIME.  AROUND ITS EASTERN PERIPHERY, MOISTURE
FROM A WEAKENING TROPICAL CYCLONE SEYMOUR HAS STREAMED NORTHEAST
INTO CA, WITH PRECIPITABLE WATER VALUES NEAR 1.5" FROM POINT
CONCEPTION NORTHWARD TO SACRAMENTO, AND 0.5"+ VALUES IN THE SIERRA
NEVADA PER GPS INFORMATION.  INFLOW AT 700 HPA IS CONVERGENT
ACROSS CENTRAL CA, WITH SPEEDS IN THE 35-45 KT WIND RANGE PER VAD
WIND PROFILES.  MUCAPES OF OVER 100 J/KG ARE SEEN IN SPC
MESOANALYSES NEAR AND INLAND OF POINT CONCEPTION.

WHILE HOURLY RAIN RATES OF UP TO 0.25" HAVE BEEN SEEN IN CA
MESONET OBSERVING SITES AS OF LATE, THE COMBINATION OF INCREASING
DIVERGENCE ALOFT, INCREASING VORTICITY ADVECTION WITH HEIGHT, SOME
COOLING ALOFT, AND INCREASING BOUNDARY LAYER MOISTURE CONVERGENCE
FROM 10Z ONWARD IS EXPECTED TO CAUSE RAIN RATES TO INCREASE LATE
TONIGHT INTO THE MORNING HOURS.  CONSIDERING THE AVAILABLE
MOISTURE, INSTABILITY, AND EXPECTED INCREASE IN THE 700 HPA WIND
TO 50+ KNOTS, 0.50" AN HOUR RAIN RATES APPEAR TO BE IN THE CARDS,
ESPECIALLY IN THE 12Z-17Z TIME FRAME AS IMPLIED BY THE 18Z SSEO
NEIGHBORHOOD PROBABILITIES.  RAINFALL OF THIS MAGNITUDE COULD
CAUSE ISSUES NEAR BURN SCARS, WHICH APPEAR MORE NUMEROUS IN THE
COASTAL RANGES BETWEEN SALINAS AND SAN LUIS OBISPO AND NEAR
LOMPOC.  BURN SCARS APPEAR MORE WIDELY SPACED BETWEEN THE SEQUOIA
AND TAHOE NATIONAL FORESTS.  THE MESOSCALE GUIDANCE SHOWS A GOOD
SIGNAL FOR LOCAL AMOUNTS OF UP TO 2" IN THE COASTAL RANGES AND UP
TO 3" IN THE SIERRA NEVADA.  FORECASTS FROM THE 00Z NAM INDICATE
THE HIGHER PEAKS OF THE SIERRA NEVADA SHOULD SEE A TRANSITION TO
SNOW BY 18Z AS THE UPPER TROUGH MAKES ITS CLOSEST APPROACH.

ROTH

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

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

LAT...LON   39922132 39622049 38982006 38381963 37581872 
            36931829 36381816 35251835 33951895 34311983 
            34462062 34742077 35142090 35992179 36442205 
            36782209 36982247 37722275 38362318 39332256