504
FXUS66 KSTO 302133
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
233 PM PDT Fri May 30 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
widespread Moderate HeatRisk. Very hot, above-normal temperatures
are expected through Saturday with areas of Major Heatrisk
through the Valley and foothills. Elevated fire weather
conditions are expected, mainly across the northern and central
Sacramento Valley, with highest potential on Monday and Tuesday
as breezy northerly winds develop. Periods of breezy onshore winds
are possible for areas to the south. Temperatures begin to cool
off slightly Sunday through Wednesday, but will remain seasonably
warm with areas of Moderate HeatRisk through the northern/central
Sacramento Valley. There are chances for isolated afternoon/early
evening mountain showers and thunderstorms Saturday through
Wednesday over the Sierra crest south of Highway 50, with highest
chances on Monday (10-20%).

&&

.Key Messages...

* Heat Advisory in effect through 8 PM Saturday for Valley,
  Delta, and foothills.

* Today:
 -Triple digit heat anticipated in the Valley and foothills today
  with widespread Moderate HeatRisk and areas of Major HeatRisk
  and near record highs this afternoon.
 -Probability of Valley high temperatures > 100F:
  --60-95%, highest across northern/central Sacramento Valley.


* Saturday:
 -Triple digit heat anticipated in the Valley and foothills late
  this week with near to record high temperatures possible.
 -Widespread Moderate HeatRisk with areas of Major HeatRisk in
  the Valley and foothills.
 -Probability of Valley high temperatures > 100F:
  --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:
  --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.
 -Elevated fire weather concerns Monday through Tuesday due to
  low relative humidity, breezy winds, and warm temperatures
  across the northern and central Sacramento Valley
 -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 the slight potential for isolated showers and
  thunderstorms on Monday (10-20%) and Tuesday (~10%), mainly
  south of Highway 50.
.Changes from previous forecast...
 -Elevated fire weather conditions through Sunday have diminished
  some with slightly lighter winds.

 &&

.AVIATION...
VFR conditions prevail across interior northern
California over the next 24 hours with mostly clear skies. Surface
winds generally below 12 kts in the Valley. For the Delta
vicinity, surface winds 10 to 15 kts with gusts 15 to 20 kts from
00Z to 12Z Saturday and again after 00Z Sunday. &&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 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.

&&

$$