393
FXUS66 KSTO 181934
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1234 PM PDT Fri Sep 18 2026

.KEY MESSAGES...

  - Seasonable temperatures and dry conditions persist over the
    weekend with generally offshore winds.

  - Isolated mountain thunderstorm chances (up to 10%) along the
    Sierra from Highway 50 southward on Monday.

  - Dry weather remainder of next week with gradual warming trend
    through the middle of the week.

&&

.DISCUSSION...

Today-Weekend:
Upper level troughing is beginning to eject eastward as of early
this afternoon and is expected to exit the region by Saturday. In
its wake, a brief period of weak ridging looks to build in over
much of the weekend. A deepening offshore trough then looks to
gradually approach the West Coast later in the day on Sunday.
Resultant weather impacts through the weekend are expected to
remain minimal with high temperatures returning to seasonable
values in the 80s to low 90s, dry conditions, and light to
occasionally breezy north to east winds gusting 15-20 mph at
times. While the approaching trough looks to track toward
central/southern California, a shift toward onshore, south to west
winds looks to arrive Sunday into Monday, introducing some
improving humidity values.

Next Week:
With ensemble guidance in general agreement on a more southerly
track of the early to mid week trough, mountain thunderstorm
chances are beginning to trend further southward as well. Isolated
thunderstorm chances up to 10% remain in the forecast, but
highest potential is anticipated along and south of the Highway 50
corridor at this time. While coverage will likely be limited at
best, primary impacts from any thunderstorms that develop will be
new fire starts from isolated lightning strikes and gusty outflow
winds. As the trough oscillates over SoCal and the Desert
Southwest into the remainder of the week, interior NorCal is on
track to remain underneath split flow aloft. This will generally
usher in a period of lighter onshore winds, and with rising
heights aloft, slightly warming temperatures into the mid to late
week period. While there is uncertainty in the exact details of
the warming next week, areas of Moderate HeatRisk will be possible
in the Valley and Delta on Wednesday and Thursday.

&&

.AVIATION...
VFR conditions expected through 18z Saturday. Gusts up to 15-20
MPH across the forecast area until 00z Saturday before weakening
in the Valley and lingering over the Sierra and Delta overnight.
Forecasts show a 20-40% chance of MVFR conditions from lower
ceilings across the Sacramento Area sites from around 12z to 16z
Saturday.

&&

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

$$