814
FXUS66 KSTO 012205
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
305 PM PDT Sun Jun 1 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...

* Today - Monday:
 -Near normal highs today with gradual warming and areas of
  Moderate HeatRisk returning by Monday.
 -Elevated fire weather concerns this evening.
 -Critical fire weather conditions develop early Monday morning
  and continue into the evening across the northern and central
  Sacramento Valley and adjacent northern Coastal Range.
  --Low relative humidity with limited overnight recovery expected
   as breezy north winds increase Sunday evening.
  --Probability of wind gusts > 30 mph: 50-95%, highest within
   northern Sacramento Valley and adjacent Coastal Range.
 -Slight shower or thunderstorm chances around 5-15% across
  Shasta County mountains this evening, returning to portions of
  the Sierra south of Highway 50 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% Wednesday PM and
  Thursday PM along the Sierra south of Highway 50.

.Changes from previous forecast...
 -Red Flag Warning has been issued over the northern and central
  Sacramento Valley and adjacent northern Coastal Range from 2 am
  to 8 pm Monday.

 &&

.AVIATION...
VFR conditions prevail over interior NorCal next 24 hours.
Surface winds around 10-15 kts, with gusts up to 20 kts from 20z
to 06z Mon. in the Valley and up to 25 kts across the Delta.
Breezy winds linger over the Northern Sac. Valley with north winds
10 to 20 kts and gusts up to 20-30 kts from 09z Mon. through 18z
Mon.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 2 AM to 8 PM PDT Monday for Central
Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and
Butte County Below 1000 Ft-Eastern Mendocino NF-Eastern Portion
of Shasta/Trinity NF-Northern Sacramento Valley to Southern
Tehama County Line Below 1000 Ft-Southeast Edge Shasta-Trinity
NF and Western Portions of Tehama-Glenn Unit.

&&

$$