423
FXUS66 KSTO 281939
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1239 PM PDT Wed May 28 2025

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



.Discussion...

.Synopsis...
Dry weather and warming temperatures continue through the
remainder of the week with slight chances for isolated mountain
showers/thunderstorms this afternoon. Areas of Moderate HeatRisk
in the Valley on Thursday will become widespread with areas of
Major HeatRisk in the Valley and foothills on Friday and Saturday.
Elevated fire weather conditions are also expected Friday and
Saturday as well. Slightly cooler high temperatures are expected
on Sunday and into early next week as a weather system drops into
the region bringing breezy winds, chances for isolated
showers/thunderstorms, and the potential for additional fire
weather conditions.

&&

.Key Messages...

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

* Today - Thursday:
 -Warming trend, with areas of Moderate HeatRisk expected in the
  Valley on Thursday.
 -Probability of Valley high temperatures > 95F:
  --30-70%, highest across northern/central Sacramento Valley.
 -Slight chance (10%) of isolated mountain thunderstorms this afternoon
  and early evening, primarily south of Interstate 80.

* 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%, highest north of Interstate 80.
  --Saturday: 50-90%, 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 Friday night > 65F:
  50-95%, highest north of I-80.
 -Hot temperatures along with very low humidity and periodically
  breezy winds will lead to elevated fire weather conditions.

* Sunday - Tuesday:
 -Cooling trend expected late weekend into early next week
  associated with an approaching weather system.
 -High uncertainty in the track of the system at this time, with
  the potential for elevated fire weather conditions in periods
  of breezier winds.
 -Some isolated thunderstorm potential on Monday and Tuesday, best
  chances (around 10-20%) along the Sierra crest.

.Changes from previous forecast...
 -Minor HeatRisk is expected today across the area, with Moderate
  HeatRisk tomorrow across the Valley & foothills.
 -Additional mountain shower/thunderstorm chances on Tuesday over
  the Sierra.

&&

.AVIATION...
VFR conditions expected next 24 hours across TAF sites in the
Valley. Periods of gusty on shore winds in the Delta and central
Sacramento Valley this afternoon/evening, with surface gusts up to
25 knots. Elsewhere, surface winds generally below 12 knots with
an occasional gust up to 20 knots through around 15z Thursday. &&

.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.

&&

$$