Vallecito, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

431
FXUS66 KSTO 292105
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
205 PM PDT Thu May 29 2025

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


.Discussion...

.Synopsis...
Warmer high temperatures are in the forecast for today with
Moderate HeatRisk in the Valley. Very hot, above-normal
temperatures are expected Friday & Saturday with widespread
Moderate HeatRisk and areas of Major Heatrisk. As a result
elevated fire weather conditions are expected in the Valley.
Temperatures begin to cool off slightly, but will remain warm
Sunday through Wednesday with areas of Moderate HeatRisk through
the northern/central Sacramento Valley. Periodically breezy winds
will lead to fire weather conditions persisting through Tuesday
mainly through the northern/central Sacramento Valley, with the
most notable days being Monday and Tuesday. Additionally, there
are chances for isolated afternoon/early evening mountain showers
and thunderstorms Saturday through Wednesday over the Sierra south
of I-80, with highest chances on Monday (10-20%).

&&

.Key Messages...

* Heat Advisory in effect from 11 AM Friday to 8 PM Saturday for
  Valley, Delta, and foothills.

* Today:
 -Warmer high temperatures are expected today with areas of
  Moderate HeatRisk expected in the Valley today.
 -Probability of Valley high temperatures > 95F:
  --40-90%, highest across northern/central Sacramento Valley.


* Friday - Saturday:
 -Triple digit heat anticipated in the Valley and foothills late
  this week with near to record high temperatures possible on
  Friday.
 -Widespread Moderate HeatRisk with areas of Major HeatRisk in
  the Valley and foothills.
 -Probability of Valley high temperatures > 100F:
  --Friday: 60-95%
  --Saturday: 50-95%, highest away from Delta breeze influenced
   areas.
 -Limited overnight relief expected across the northern/central
  Sacramento and northern San Joaquin Valleys and thermal belts
  across the foothills.
 -Probability of Valley low temperatures > 65F:
   --Friday morning: 50-95%
   --Saturday morning:40-90%
 -Hot temperatures along with very low humidity and periodically
  breezy winds will lead to elevated fire weather conditions.

* Sunday - Wednesday:
 -Slightly cooler, but still warm high temperatures with areas of
  Moderate HeatRisk.
 -Increased onshore flow expected on Sunday through the Delta and
  southern Sacramento area, with northerly winds developing on
  Monday and Tuesday through the northern and central Sacramento
  Valley.
 -There is isolated thunderstorm potential on Monday (10-20%) and
  Tuesday (~10%), mainly south of I-80.

.Changes from previous forecast...
 -Elevated fire weather conditions continue through Tuesday due to
  low relative humidity, breezy winds, and warm temperatures across
  the northern and central Sacramento Valley.
 -Marginal chances for isolated afternoon/evening showers and
  thunderstorms over the Sierra south of I-80, Saturday-Wednesday

&&


.AVIATION...
VFR conditions expected next 24 hours across interior NorCal.
Mostly clear skies and surface winds below 12 knots in the Valley,
with surface winds of 15 knots, gusts to 20 knots in the Delta
vicinity around 00z to 11z Friday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM Friday to 11 PM PDT Saturday for
Carquinez Strait and Delta-Central Sacramento Valley-Motherlode-
Mountains Southwestern Shasta County to Western Colusa County-
Northeast Foothills/Sacramento Valley-Northern Sacramento Valley-
Northern San Joaquin Valley-Shasta Lake Area / Northern Shasta
County-Southern Sacramento Valley.

&&

$$