Grass Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

653
FXUS66 KSTO 132107
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
207 PM PDT Sun Jul 13 2025

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

.DISCUSSION...

.SYNOPSIS...
Hot weather continues through Monday with Moderate to locally
Major HeatRisk. Increasing Delta breeze influence will bring minor
cooling and overnight relief over the weekend and into next week
in the Delta and adjacent Valley locations. Dry weather and
periodically breezy onshore winds are expected through Friday
alongside temperatures returning to near normal mid to late week.

&&

.KEY MESSAGES...

* Heat Advisory remains in effect through 11 PM Monday evening
  for the northern/central Sacramento Valley and surrounding
  foothills and mountain locations.

*  Today-Monday:

 - Broad troughing and attendant northwesterly flow continue as
   high heights aloft persist.
 - Widespread Moderate HeatRisk with areas of Major HeatRisk across
   interior NorCal.
 - Smoke will continue to impact areas in the vicinity of the
   Green Fire, with occasional northerly winds spreading smoke and
   haze southward through the Valley.
 - Locally breezy northerly flow in the northern/central
   Sacramento Valley and adjacent terrain, mainly in the overnight
   through morning timeframe.
 - Increasing onshore flow and Delta Breeze influence expected
   through the weekend, bringing minor cooling and overnight
   relief to the Delta and adjacent Valley.
 - Low daytime relative humidity with moderate to poor overnight
   recoveries over foothills and mountains.
 - Low (5-10%) chance for isolated thunderstorms across the high
   terrain of Shasta County during the afternoon/evening hours on
   Monday.

*  Tuesday-Saturday:

 - Upper level pattern remains largely persistent with broad
   troughing/northwesterly flow across interior NorCal. Some
   signals for ridging and increasing heights aloft into next
   weekend.
 - A slight cool down to more seasonable temperatures mid to late
   week, followed by a gradual warming trend by next weekend.
 - Periodically breezy onshore flow expected to persist in the
   afternoon and evening, shifting toward terrain driven
   influence during the overnight hours.
 - Strongest onshore winds anticipated on Tuesday as a subtle
   shortwave ejects through the region.
 -- Probability of Wind Gusts > 30 mph: 60-90% throughout the
    Delta and Sacramento Valley.
 - Persistent and periodic late day wind gusts 20 to 30 mph
   anticipated throughout the Delta and vicinity each day.

.Changes from previous forecast...
 - Minimal changes from the previous forecast.

&&

.AVIATION...
Wildfire smoke will result in MVFR and IFR conditions at times in
the northern Sacramento Valley, including KRDD and KRBL. VFR
conditions expected elsewhere across interior Northern California
over the next 24 hours. West-southwest winds will be breezy
through the Delta with gusts 15 to 25 kts through 16Z Monday.
Elsewhere, sustained speeds generally at or below 12 knots over
the next 24 hours, with periodic gusts 15 to 20 kts in the Valley
between 22Z Sunday and 04Z Monday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 11 PM PDT Monday for Burney Basin / Eastern
Shasta County-Central Sacramento Valley-Mountains Southwestern
Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Shasta
Lake Area / Northern Shasta County-Western Plumas County/Lassen
Park.

&&

$$