658
FXUS66 KSTO 081150
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
350 AM PST Sat Feb 8 2025


.SYNOPSIS...
Cold weather and breezy winds through this weekend. Active
weather returns mid to late next week bringing renewed chances for
rain, mountain snow, and gusty winds.

&&

.DISCUSSION...
Mostly clear skies are being observed across interior Northern
California per GOES-West nighttime imagery with isolated fog and
low stratus bring observed in the southern Sacramento Valley.
Latest hires guidance shows a 20-40% chance of fog and low stratus
development along the eastern half of the Valley from I-80
southward until roughly 10 AM. Temperatures are on track to drop
down to near or below-freezing this morning as clear skies promote
enhanced radiational cooling. These colder morning lows stick
around through Tuesday with Valley lows in the upper 20s to mid
30s, temperatures in the 20s to low 30s in the foothills, and
single digits to teens in the mountains. NBM probabilities
indicate with a 40 to 70% chance of 32 or less in the
Valley/foothills and a 50 to 70% chance of less than 15 in the
mountains. Take steps to protect pets, people, plants, and pipes
from these cold temperatures! And make sure to dress appropriately
for the cold.

Gusty north to northeast winds pick up tonight continuing into
Monday morning with gusts 25 to 35 mph along the I-5 corridor in
the Sacramento Valley and funneling through gaps in the Sierra.
Strongest winds will be tonight into Sunday morning with a 40 to
65% chance of winds gusting to 35 mph or higher, primarily along
the western side of the Sacramento Valley.
&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Ensemble guidance continues to show strong agreement in the
general progression of the upper level pattern mid to late next
week. A retrograding trough looks to back build from the
Intermountain West toward the West Coast reinforcing an
exceptionally dry airmass aloft. This will lead to enhanced
radiational cooling effects overnight resulting in cold morning
temperatures and below normal highs. A deepening trough offshore
is forecast to rapidly progress toward the Pacific Northwest/northern
California by Wednesday, bringing a return to active weather
across the mid to late week period. Stagnant near-surface cold
air will introduce the potential for low elevation snowfall into
portions of the northern Sacramento Valley and toward Sierra
foothills locations.

The primary uncertainty regarding lower elevation snowfall with
this system is largely centered around the timing of warm air and
moisture advection into the region. As of right now, best chances
for lower elevation snow would be overnight Wednesday into
Thursday morning as moisture advects inland while temperatures
remain near-freezing temperatures. Forecast uncertainty is high
regarding this scenario, but probabilities of up to 2 inches
around Redding and Shasta Lake areas are 15 to 30 percent. Similar
chances exist into the Nevada City and Pollock Pines areas as
well.

Despite that specific uncertainty, periods of moderate to heavy
rain and mountain snow are expected elsewhere as this system moves
through. Current probabilities of exceeding 1 foot of snowfall
above 5000 feet sit around 50 to 70 percent leading to potential
mountain travel impacts.

Gusty southerly winds are also in play on Thursday as the trough
progresses. Across the Valley/Sierra foothills, there is a 40 to
60% chance of gusts greater than 40 mph; And a 50 to 70% chance
for gusts greater than 55 mph over the Sierra. Forecast confidence
generally increases 3 to 4 days out from a given event, so be
sure to monitor the forecast into next week as details become
clearer.

&&

.AVIATION...
Generally, VFR conditions across interior NorCal over the next 24
hours outside of a chance (15-30%) for reduced visibilities from
BR across the eastern portions of the Valley south of I-80 until
18z Sat. Light northerly winds expected with gusts 15-20 kts into
Central Valley after 21z Saturday and then weakening after 03z
Sunday.

&&

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

$$