Area Forecast Discussion
Issued by NWS Sacramento, CA
FXUS66 KSTO 021216
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SACRAMENTO CA
416 AM PST Mon Dec 2 2013
A fast moving cold front will sweep southward across the region
later today into early Tuesday bringing a chance of precipitation.
A much colder airmass will settle in across northern California
by mid-week with the potential for widespread freeze conditions in
The strong ridge that brought the dry and unseasonably mild
weather over the weekend is breaking down as upper low over
western Canada drops south. Most of the forecast area is expected
to remain dry through the daylight hours today, but increasing
high clouds will result in cooler temperatures across NorCal.
A fast moving cold front will sweep southward through the region
tonight and early Tuesday. NAM continues to be the fastest of the
models with showers winding down by later Tuesday. Breezy
northerly winds will develop across the region in the wake of the
front and strengthening subsidence will promote clearing skies.
A colder and drier airmass settles over the region for the second
half of the week with strong negative cold anomalies. However,
mixing due to breezy northerly winds will likely keep temperatures
from dropping too low in much of the valley early Wednesday. The
winds will weaken by later Wednesday, so colder overnight lows are
expected late in the week.
.Extended Discussion (Friday through Monday)...
A cold airmass will be fully entrenched across the Intermountain
West by late this week with light winds and good radiational
cooling. However, increasing clouds on Saturday due a reinforcing
cold shot moving southward will limit the radiational cooling
overnight Friday into Saturday and again into Sunday morning. Even
so, expect lows in the upper 20s to low 30s across the Central
Valley, with single digits to low 20s in the mountains. This
secondary cold shot will likely keep temps cold with a slight
chance of precipitation. But with the cold air already in place,
snow ratios may be rather high and allow for greater than
anticipated snow accumulations over the Sierra...with low snow
Then on Monday and beyond, the models are out of phase and are
struggling to make sense of a pattern change as the models try to
resolve the potential breakdown of a rather large blocking ridge
over the eastern Pacific Ocean. The GFS has a more progressive
solution, the ECMWF still tries to hold onto the ridge, and GEM is
somewhere in between. In any event, we introduced a slight chance
of precipitation on Monday. JCLAPP
Local MVFR to IFR conditions continue in the northern San Joaquin
Valley this morning with BR/HZ and local MVFR possible in Sac
metro area with patchy ground fog possible 13z to 16z,
particularly surrounding KSMF.
Approaching cold front moves into the area tonight, bringing
increasing clouds with BKN050 to BKN100 CIGS for Valley TAF sites.
Expecting a chance of showers in the Valley from around KCIC/KOVE
northward by this afternoon, with showers likely in the Sierra
along with lowering snow levels. Potential MVFR ceilings in
southern Sac and northern San Joaquin Valleys later tonight.
Increasing gusty southwest winds up to 50 kts over Sierra ridges
this afternoon and tonight ahead of the front. JCLAPP
Hard freeze watch remains in effect from late Wednesday night
through Saturday morning for the Sacramento Valley, Northern San
Joaquin Valley, Delta and surrounding foothills below 2000 feet
including southern Lake County.