Alta Sierra, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

819
FXUS66 KSTO 012013
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1213 PM PST Sun Nov 1 2026

For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.

.KEY MESSAGES...

 - Drier with breezy north to east winds today and potential
   patchy Valley fog into Monday morning

 - Quick moving system brings shower/isolated thunderstorm chances
   Tuesday-Wednesday

 - Below normal temperatures through mid week trend near to
   slightly above normal heading toward the weekend alongside
   otherwise mostly dry conditions

&&

.DISCUSSION...

Today-Monday:
As the early weekend system is already making its way eastward as
of midday today with a brief period of breezy north to east winds
and dry weather expected in its wake. Strongest north winds
gusting 15-20 mph are expected through this afternoon in the
Valley along and west of the Interstate 5 corridor while breezier
downslope east winds gusting 20-30 mph along the Sierra wait to
increase until the evening and overnight hours. While the flow
pattern aloft will be conducive to mostly sunny skies today there
is some potential for patchy fog/low clouds to develop for Valley
locations generally along and south of the Interstate 80 corridor
early Monday morning. Current probabilities for patchy fog
development sit around 30-40% at this time, with the depth of dry
air from northerly winds today being the primary limiting factor.

With mostly sunny skies today, high temperatures look to remain
around seasonal normals, in the 60s for the Valley/foothills and
50s to 60s throughout the mountains. A chilly night is then in
store for much of interior NorCal as radiational cooling allows
overnight lows to drop into the lower 40s in the Valley/foothills
and 20s to 30s at higher elevations. Despite the dry and sunny
conditions today, a deepening shortwave trough is already evident
off shore via latest satellite water vapor imagery. As this system
approaches the coast on Monday, look for gradually increasing
cloud cover across the area and slightly cooler, but still
seasonable high temperatures into Monday afternoon.

Tuesday-Wednesday:
The aforementioned offshore trough is then expected to traverse
interior NorCal Tuesday into Wednesday. Ensemble guidance remains
in relatively steady agreement on increasing chances for showers
and isolated thunderstorms by midday Tuesday, albeit with some
minor differences in exact timing. At this time, thunderstorm
chances remain around 5-8% with instability staying largely near
the coast as the system progresses. Regardless, of the magnitude
of available instability some brief periods of moderate to heavy
rainfall may be possible in the Valley as a rather robust cold
frontal passage is anticipated. Resultant rainfall totals may vary
as a result of this mesoscale feature, but at this time,
probabilities for precipitation greater than 0.25" Tuesday-
Wednesday sit a 30-50%. Forecast snow levels have trended slightly
lower, closer to 6000`-7000` now, but overall light accumulations
around an inch or less and minimal snowfall impacts are currently
still anticipated.

Mountain shower chances likely linger into early Wednesday, but
the abrupt eastward ejection will see precipitation chances
dwindling by midday Wednesday at the latest. An additional period
of increasing north to east winds is also anticipated as the
system departs with similar splits of breezier north winds through
the Valley/Delta west of Interstate 5 in the afternoon
transitioning to breezy downslope easterlies along the Sierra
overnight into Thursday.

Late Week Into Next Weekend:
Forecast certainty remains somewhat middling for the late week
period into next weekend. Prevailing guidance indicates mostly dry
northwesterly flow aloft through the end of the week followed by
a brief period of ridging and higher heights aloft through the
weekend. The primary uncertainty lies incumbent upon any subtle
shortwaves ejecting within the northwesterly flow aloft prior to
the weekend ridging. At this time, ensemble guidance is trending
toward largely drier and warmer attendant weather across this
portion of the extended forecast for interior NorCal, hinting at
only some low potential for light showers to periodically impact
locations north of the Interstate 80 corridor at this time.

&&

.AVIATION...
VFR conditions are generally expected to prevail at TAF sites
through 06z Monday with a 30-40% chance for reductions to MVFR in
patchy fog/low clouds at SCK/MOD and Sacramento sites into Monday
morning. Otherwise light winds less than 12 kts persist across the
forecast period, predominantly from a north to east direction
area wide.

&&

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

$$