494
FXUS66 KSTO 152006
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
106 PM PDT Thu May 15 2025

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

.Discussion...

.Synopsis...
Drier and warmer weather persist through Friday, with
occasionally breezy winds through the end of the week. The next
weather system then looks to arrive by the weekend, bringing
mountain/foothills thunderstorm chances Saturday, followed by
gusty and drying north winds Sunday into next week. As a result,
critical fire weather conditions are anticipated Sunday and Monday
throughout the Valley and Delta due to the gusty winds and
expected low relative humidity. Dry and hot weather then looks to
follow, with areas of Moderate HeatRisk and elevated fire weather
conditions through mid next week.

&&

.Key Messages...

* Fire Weather Watch in effect from 8 am PDT Sunday through 8 pm
  PDT Monday for Valley and Delta locations below 1000 feet.

* Today-Friday:
 -Dry weather, warm temperatures, and periodically breezy winds
  persist with areas of Minor HeatRisk in the Valley.

* Saturday:
 -Weather system begins to drop southward from Pacific NW.
 -15-30% probability of isolated thunderstorms across northeast
  foothills and Sierra/southern Cascades from Interstate 80
  northward.
 -Temperatures cooling to near normal, with breezy winds
  throughout the day.

* Sunday - Monday:
 -Current ensemble trends indicate the expected weather system
  following an inside slider trajectory through the region.
 -Gusty north to east winds expected to develop Sunday and Monday
  as this system progresses, with lingering breezy winds into
  Tuesday.
 -Probability of gusts 40 mph or higher:
 --Sunday: 40-60%, highest along and west of I-5 in the
  Sacramento Valley.
 --Monday: 20-40% across the northern/central Sacramento Valley
  and Delta.
 -Critical fire weather conditions expected Sunday and Monday, due
  to the combination of gusty northerly winds and low relative
  humidity in the Sacramento Valley.

* Tuesday - Wednesday:
 -Warming trend expected early to mid next week, with areas of
  Moderate HeatRisk across the Valley.
 -North to east winds expected to remain diurnally breezy while
  dry conditions prevail.
 -Elevated fire weather conditions anticipated.

.Changes from previous forecast...
 -Fire Weather Watch issued for Sunday morning into Monday
  evening for Valley and Delta locations below 1000 feet.
 -Shower and thunderstorm chances shifting primarily to
  Interstate 80 northward on Saturday.
 -Elevated fire weather conditions loo to persist into mid next
  week.
 -Areas of Moderate HeatRisk for the Valley expected next week.

&&

.AVIATION...
VFR conditions expected to prevail at TAF sites next 24 hours.
North-northwest winds remain breezy through the day, then becoming
lighter after 06z. Winds generally expected to remain 12 kts or
less, although some southwesterly gusts to 20 kts possible with
Delta breeze influence 22z-05z. Breezier north winds are expected
after 12Z through the northern and central Sacramento Valley with
gusts up to 20 kts.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Sunday morning through Monday evening
for Carquinez Strait and Delta-Central Sacramento Valley in
Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below
1000 Ft-Northern Sacramento Valley to Southern Tehama County
Line Below 1000 Ft-Northern San Joaquin Valley in San Joaquin
and Stanislaus Counties Below 1000 ft-Southern Sacramento Valley
in Yolo-Sacramento Far Western Placer, southern Sutter and
Solano County Below 1000 Ft.

&&

$$