Grass Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

459
FXUS66 KSTO 271834
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1134 AM PDT Sat Jun 27 2026

.KEY MESSAGES...

 - Chances for isolated mountain showers/thunderstorms today.

 - Elevated fire weather conditions Sunday-Monday due to increased
   North winds across portions of the Valley.

 - Cooler temperatures and breezy onshore flow expected Tuesday
   onward.

&&

.DISCUSSION...

A trough from the Gulf of Alaska continues to move through the
area today, bringing isolated light showers and a 10-20% chance
for isolated mountain thunderstorms this afternoon. Primary areas
of concern today are over the southern Cascades and eastern
Shasta County. Additionally, enhanced onshore winds are expected
through the Delta and Valley through today introducing cooler
temperatures and higher humidities throughout the area.

As the trough exits into the Great Basin area, north winds
increase on Sunday through the western portions of the Sacramento
Valley & Delta. This will result in renewed fire weather
conditions Sunday into Monday. Strongest winds are expected Sunday
morning. Since the strongest winds are forecast during the
morning hours, they will not coincide with the lowest relative
humidities. That being said, winds will still remain gusty through
the afternoon hours when relative humidities will be in the teens
to low 20s. The majority of elevated fire weather conditions will
be in the northern Sacramento Valley along and west of I-5. Monday
sees significantly weaker winds and therefore also lower fire
weather concerns.

Deterministic EC and GFS continue to depict a lobe of energy
phasing out of the exiting trough, though now primarily on
Monday. This may introduce additional mountain shower and
thunderstorm chances north of I-80. The overall environment will
be dry which may negate any shower development, however, the
feature will be closely monitored for any significant changes
and/or additional fire weather concerns.

Moving further into the week, another cooling trend is expected
Tuesday and beyond, resulting in below normal temperatures across
interior NorCal and periods of breezy onshore flow in the
forecast.

&&

.AVIATION...

General VFR conditions are expected over the next 24 hours. South
to southwest wind gusts to 15 to 20 kts until 07Z Sunday the in
central/southern Sacramento Valley, and 15-25 kts in the Delta
until 10Z Sunday. Winds shift out of the north through the Sac
Valley after 10Z Sunday, with gusts 15 to 25 kts through 00Z
Monday. 10-15% chance isolated thunderstorms in eastern Shasta
County and the southern Cascades through 05z Sunday bringing local
MVFR/IFR conditions.

&&

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

&&

$$