Flooding and Heavy Rain in California, December 9 to 12, 2016

Area Forecast Discussion
National Weather Service Sacramento CA
357 AM PST Fri Dec 9 2016

.SYNOPSIS...
Wet pattern continues going into the weekend as more weather
systems move through northern California. High snow levels
expected. A brief break in the wet pattern early next week except
for northern most areas. Periods of rain and high elevation
mountain snow returning by next Tuesday then continuing through
the end of the week.

&&

.DISCUSSION...
Moist zonal flow continues over the western U.S. A short wave
within this zonal flow is bringing a few light showers over the
Sierra and foothills at this time. Snow levels are quite high at
above 8000 feet due to warm advection ahead of a weak front now
just off the coast. Some fog has formed in the central valley this
morning but extensive cloud cover should keep this from becoming
significantly dense. The weak system moving through the north
state today will bring continued periods of precipitation but qpf
amounts area not exceptionally high and snow levels should remain
mainly above pass levels. Therefore...impacts should remain
relatively minor today. A more significant disturbance is expected
to move through the region on Saturday continuing the wet weather
pattern. Overall precipitation totals in the valley will stay
fairly low but orographics over the Sierra will bring moderate
precipitation there. Again, snow levels should remain above pass
levels so impacts will be limited. A slight upper ridging over the
west coast on Sunday should shift the precipitation line
northward. This should bring a break in the wet pattern for much
of the forecast area except for the northern counties.
Precipitation remains over the northern zones on Monday under a
slight upper ridging. Snow levels lower Sunday and Monday but
should remain above the lower passes where precipitation is
expected. Cloud cover and cooler airmass will keep daytime highs a
little below normal.

&&
.EXTENDED DISCUSSION (Tuesday THROUGH Friday)

Pacific moisture plume will bring precipitation into the area
Tuesday into Wednesday, focused over the northern Sierra. Snow
levels will initially be below pass levels, then rise above them
during the day Wednesday. This could bring some travel impacts in
the mountains. Models diverge after Wednesday, with high
uncertainty on timing of following systems. Will keep general
chances of precipitation through the extended, though there will
likely be breaks at times. Late in the week there are hints of a
cold system with low snow levels, but timing and precipitation
amounts are uncertain. EK

&&

.AVIATION...

Widespread MVFR CIGS/VIS with areas IFR will continue next 24
hours under warm-advection regime. Locally strong southwesterly
winds across the higher elevations of the northern Sierra Nevada.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

Special Weather Statement
National Weather Service Sacramento CA
453 AM PST Fri Dec 9 2016

CAZ013>019-063-064-066>069-100100-
Shasta Lake Area / Northern Shasta County-
Burney Basin / Eastern Shasta County-Northern Sacramento Valley-
Central Sacramento Valley-Southern Sacramento Valley-
Carquinez Strait and Delta-Northern San Joaquin Valley-
Mountains Southwestern Shasta County to Northern Lake County-
Clear Lake/Southern Lake County-
Northeast Foothills/Sacramento Valley-Motherlode-
Western Plumas County/Lassen Park-
West Slope Northern Sierra Nevada-
Including the cities of Shasta Dam, Burney, Redding, Red Bluff,
Chico, Oroville, Marysville/Yuba City, Sacramento,
Fairfield/Suisun, Stockton, Modesto, Alder Springs, Lakeport,
Paradise, Grass Valley, Jackson, Chester, Quincy, and Blue Canyon
453 AM PST Fri Dec 9 2016

...Wet Weather Continues into the weekend...

.Impacts...

  *Travel delays due to slick roads and high elevation mountain
   snow. Snow levels around 6500 to 7500 feet over Sierra passes
   with some travel impacts possible.

  *Local road flooding possible in poor drainage areas.

.Timing and Strength...

   *Next wave of precipitation expected today with another round
    on Saturday. Precipitation decreasing on Sunday except
    northern counties

   *Rain totals in the central valley ranging from a half to one
    and one quarter inches with two inches or more in the
    foothills.

   *Snow totals today through Saturday ranging from five inches
    near Sierra pass levels with up to a foot and a half highest
    elevations of the Sierra crest.