138
FXUS66 KSTO 312123
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
123 PM PST Sat Jan 31 2026


.KEY MESSAGES...

 - Dry weather with patchy fog in the Valley and lower foothills
   expected through Sunday.

 - Precipitation chances continue to trend down for Sunday into
   early Monday morning.

 - Dry weather continues next week with above-normal high
   temperatures and chances for AM fog.

&&

.DISCUSSION...

...Saturday through Sunday...
Ridging continues to dominate the pattern overhead today resulting
in dry conditions. The potential for widespread dense fog returns
tonight into tomorrow morning with current guidance indicating a
50 to 80% chance of visibilities less than 1/2 mile across the
Delta, central/southern Sacramento Valley, and northern San
Joaquin Valley. Highest chances for dense fog exist in the
southern Sacramento and northern San Joaquin valleys. A Dense Fog
Advisory is in effect from 11 PM tonight to 12 pm PST Sunday for
the aforementioned areas. Be sure to slow down and use low-beam
headlights if fog is encountered while driving.

A weak trough will disrupt ridging aloft on Sunday bringing a
nonzero chance for isolated light rain over Shasta County and the
Coast Range, but precipitation chances continue to trend drier
with the latest runs. Widespread fog chances return Sunday night
into Monday morning.


...Monday through Friday...
Ridging builds back in on Monday, with dry and warmer weather
anticipated across interior NorCal along with continued chances
for morning fog. North to east winds will be breezy through the
northern and central Sacramento Valley and the Sierra
mountains/foothills on Monday with gusts 15-25 mph at times. These
winds will work against widespread dense fog development in the
central Sacramento Valley, but isolated coverage is still possible
in the southern Sacramento and northern San Joaquin valleys
Tuesday night.

Temperatures will follow a warming trend, climbing to above-
normal by midweek as ridging continues to strengthen overhead.
This will result in strong inversions that will keep conditions
warm and dry in the foothills through midweek. Otherwise, breezy
offshore flow is expected at times.

Ensemble guidance highlights another shortwave trough approaching
the region toward late week which is expected to bring cooler
temperatures.

&&

.AVIATION...

Lingering MVFR conditions this afternoon mainly in the northern
San Joaquin Valley from BR/HZ, elsewhere VFR conditions through
around 03z Sunday. BR/FG to develop in the southern Sacramento
Valley, Delta, and northern San Joaquin Valley resulting in
IFR/LIFR conditions through around 20z Sunday. Surface winds
below 12 kts across the region.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory from 11 PM this evening to noon PST Sunday
for Carquinez Strait and Delta-Central Sacramento Valley-
Northern San Joaquin Valley-Southern Sacramento Valley.

&&

$$