River Flood Warning 3, NWS Sacramento, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
1003 AM PST Wed Dec 10 2014

.Synopsis...
Light fog this morning with increasing clouds ahead of approaching
weather system. A Strong Pacific storm impacts the area late today into
Friday bringing heavy precipitation including significant mountain
snow and strong damaging winds. A mainly dry weekend is expected
with the next chance of precipitation early next week.

&&

.Discussion...
Initial rain band remains off the coast and is a bit slower than
previous model runs indicated. Band will move over the coastal
range/western Sac valley/Shasta county after 3 pm. May need to
adjust details and timing of Major storm moving into NorCal
Tonight and Thursday...but current forecast is on track. No
morning update will be needed.

.Previous Discussion...
Plenty of clouds streaming over the north state this morning ahead
of strong Pacific frontal system now poised just off the coast.
Cloud cover and slightly higher wind has kept fog from becoming
dense this morning so canceled dense fog advisory for the
morning. Focus turns to offshore frontal system forecast to move
into northwest California this afternoon. Blended TPW image shows
moisture plume associated with this system topping 1.75 inches.
Strong UVV especially early Thursday will ring out this moisture
bringing heavy rain and higher elevation snowfall at times.
Meanwhile...tight surface and upper level gradients are predicted
for strong winds. Models in fairly good agreement in shifting the
main frontal band through the central valley late Thursday night
or early Friday. Several warning products out at this time to
account for associated incoming weather. The main adjustments to
these warnings overnight included...Raising snow levels slightly
in the winter storm products which should remain higher before
cold air reaches the Sierra Thursday night. Separating the flood
watch into northern and southern zones to account for timing of
frontal movement north to south. And finally...Separating the
Blizzard warning over the Sierra into northern and southern
sections similar to flood warning timing and shortening the
duration to account for drop off in winds by Friday morning as
well as drop off in precip intensity. Most areas should see a
significant drop off in winds Thursday afternoon as pressure
gradients relax. Extensive cloud cover on Thursday should limit
surface heating so limited instability should limit thunderstorm
potential but isolated thunderstorms will remain possible. A
little better thunderstorm threat exists on Friday with some
partial clearing possible for a little more surface heating with
California remaining under cyclonic flow through the day Friday.
Upper ridging slides over the west coast Saturday for an end to
the precip threat and warmer daytime highs. Night time valley fog
returns Saturday morning under clearing skies.

&&

.Extended Discussion (Sunday through Wednesday)

High pressure remains over Northern California through Sunday,
bringing another day of drier weather. The dry period will remain
short-lived however, as another Gulf of Alaska trough moves
through the region early next week. Medium-range models are in
fair agreement bringing modest precipitation totals across much of
the area Monday, with continued chances for showers into midweek.
This should be a colder (but weaker) system than this Thursday's
storm, with snow levels currently forecast to be around 4000-5000
ft.

Dang

&&

.Aviation...

IFR/LIFR conditions with patchy dense fog will persist across the
Valley through 20z today. A wet and windy storm will begin to
move inland later today. This system will bring MVFR/IFR
conditions beginning near KRDD-KRBL with moderate rain after 00z
Thu. Winds will pick up this afternoon, and gusts up to 60-65 mph
will be possible in the Valley Wednesday night through Thursday
morning. Airport Weather Warnings have been issued for Redding and
Stockton Airports for the winds.

Dang

&&

.STO Watches/Warnings/Advisories...
high wind warning from 9 pm this evening to 2 pm pst thursday
west slope northern sierra nevada...western plumas county/lassen
park.

flood watch from 10 pm pst this evening through friday evening
burney basin / eastern shasta county...central sacramento
valley...clear lake/southern lake county...mountains
southwestern shasta county to northern lake county...northeast
foothills/sacramento valley...northern sacramento valley...
shasta lake area / northern shasta county...western plumas
county/lassen park.

flood watch from 10 pm pst this evening through friday evening
carquinez strait and delta...motherlode...southern sacramento
valley...west slope northern sierra nevada.

blizzard warning from 7 am thursday to 4 am pst friday above
6500 feet in the west slope northern sierra nevada.

high wind warning from 9 pm this evening to 2 pm pst thursday
burney basin / eastern shasta county...carquinez strait and
delta...central sacramento valley...clear lake/southern lake
county...motherlode...mountains southwestern shasta county to
northern lake county...northeast foothills/sacramento valley...
northern sacramento valley...northern san joaquin valley...
shasta lake area / northern shasta county...southern sacramento
valley.

flood watch from thursday morning through friday evening
northern san joaquin valley.

&&