Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 082249
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
249 PM PST Sun Dec 8 2013
A very cold airmass will remain over Northern California through
at least midweek, bringing overnight hard freeze conditions each
Strong high pressure off the coast with low pressure moving
through the Rockies has produced an amplified ridge that is
bringing in cold Arctic air from Canada into California. The
pattern will be about the same for the next day before some slow
gradual modification starts to change the pattern.
High pressure building into the Great Basin will produce breezy
conditions tonight over the western slopes for exposed areas. Wind
chills for those areas will likely make temperatures feel about 10
to 15 degrees colder than the air temperature.
Hard freezes expected through Wednesday and may take until Friday
before temperatures warm enough at night to drop any concern of a
hard freeze. Some locations could be nearing or reaching record
lows the next couple of mornings. The coldest locations will
likely be reaching the freezing mark by 8 pm with all other
locations reaching the freezing mark before midnight the next few
days. 12 plus hours of freezing temperatures are expected for the
coldest locations. Temperatures will warm above freezing each
morning between 9 and 11 am.
Some gradual modification of the lows will occur each night but
more noticeably Monday night and Tuesday night for the thermal
belt areas as warmer air starts to modify those temperatures in
the hills. The foothill valley locations will not see as much of
a warm up though.
Some Record lows for Dec 9th Sacramento 23/1932, Sac Exec 21/1972,
Stockton 23/1972, Modesto 22/1972, Redding 21/1972,
Red Bluff 20/2009.
Some Record lows for Dec 10th Sacramento 22/1932, Sac Exec 23/1972,
Stockton 25/1980, Modesto 24/1972, Redding 20/1932,
Red Bluff 20/2009.
.Extended Discussion (Thursday through Sunday)
Models now have some general agreement in swinging an East
Pacific trough into the West Coast early Friday. The GFS is much
deeper and wetter (spreading precip to most of our area) than the
ECMWF (which only brushes us from Shasta County northward). Model
reliability plots continue to show very low confidence, so have
kept only a chance to slight chance for areas north of Sacramento
(in line with climatology for this time of year).
Gradual warming trend continues through the extended forecast,
though the tricky part will be how fast cold air erodes in high
mountain basins such as the Burney and Lake Almanor areas. Models
are indicating that the Friday trough will be enough to mix out
the lingering arctic air, although they may be overdoing it.
Extended models return to westerly flow by next weekend with the
possibility of some light precip grazing our northern areas as a
system pushes through the Pacific NW. Meanwhile, the latest
guidance shows seasonal or even above normal temperatures
possible by the end of the week. -DVC
VFR conditions will prevail for next 24 hours across much of
Interior NorCal. Local areas of MVFR possible in portions of Southern
Sacramento & Northern San Joaquin Valleys between 08-16z which may
impact KSAC and KSCK vicinities. Northerly winds in valley of 5-15
kts this evening into tomorrow. Valley winds will be lightest
overnight and early morning. Winds aloft will be moderate North to
East flow over higher terrain with sustained winds around 30 kts
over ridges and locally stronger gusts. Mountain winds are
forecast to lessen after Monday morning. JBB
Hard Freeze Warning until 8 AM PST Wednesday Carquinez Strait and
Delta...Central Sacramento Valley...Northern Sacramento
Valley...Northern San Joaquin Valley...Southern Sacramento Valley.
Hard Freeze Warning until 8 AM PST Wednesday below 2000 feet in
the Clear Lake/Southern Lake County...Motherlode...Northeast