851
FXUS66 KSTO 312001
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
101 PM PDT Sat May 31 2025

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

.Discussion...

.Synopsis...
Following another afternoon of well above normal temperatures
today, warm and dry weather is expected to persist from Sunday
into next week alongside periodically breezy winds as troughing
aloft builds into the region. Resultant elevated fire weather
conditions are expected at times during periods of strongest
winds. Additionally, some 5-15% PM mountain shower/thunderstorm
chances are anticipated today & Sunday and Thursday & Friday,
primarily along the Sierra south of Interstate 80. Otherwise,
predominantly Moderate HeatRisk expected across interior NorCal
through the week ahead.

&&

.Key Messages...

* Heat Advisory in effect through 11 PM this evening for Valley,
  Delta, and foothills.

* Today:
 -Triple digit heat continues in the Valley and foothills 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.
 -Hot temperatures along with very low humidity and periodically
  breezy winds will lead to elevated fire weather conditions.
 -Slight thunderstorm chances around 5-15% this afternoon/evening
  along the Sierra south of Interstate 80.

* Sunday - Monday:
 -Near normal highs Sunday with additional warming and areas of
  Moderate HeatRisk returning by Monday.
 -Elevated fire weather concerns, particularly Sunday evening -
  midday Monday across the northern and central Sacramento
  Valley.
  --Low relative humidity with limited overnight recovery expected
   as breezy north winds increase Sunday evening.
  --Probability of wind gusts > 30 mph: 50-80%, highest within
   northern Sacramento Valley.
 -Slight thunderstorm chances around 5-15% across Shasta County
  mountains on Sunday, returning to portions of the Sierra south
  of Interstate 80 on Monday.

* Tuesday - Friday:
 -Broad northwesterly flow aloft expected to persist through the
  week with some increasing heights aloft.
 -Periodically breezy winds expected to continue within this flow
  pattern as temperatures settle slightly above normal with areas
  of Moderate HeatRisk.
 -Probability of Valley high temperatures > 95F:
  --Northern/Central Sacramento Valley: 60-90%
  --Delta, S. Sacramento Valley, N. San Joaquin Valley: 20-40%
 -Slight thunderstorm chances around 5-15% Thursday and Friday PM
  along the Sierra south of Interstate 80.

.Changes from previous forecast...
 -Potential for elevated fire weather conditions across the
  northern/central Sacramento Valley increasing for the Sunday
  evening through midday Monday period.

&&

.AVIATION...
VFR conditions prevail over interior NorCal next 24 hours.
Surface winds around 10-15 knots, gusts up to 20 knots in the
northern Sacramento Valley from 08z to 18z tomorrow. Surface winds
in the Delta around 15 knots with gusts up to 25 knots around 21z
today through 08z tomorrow.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 11 PM PDT this evening 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.

&&

$$