119
FXUS66 KSTO 162032
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
132 PM PDT Fri May 16 2025

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

.Discussion...

.Synopsis...
Dry, warm, and breezy weather persists today, before a weather
system arrives over the weekend. A slight chance of
mountain/foothills thunderstorms north of Interstate 80 Saturday,
is then followed by gusty and drying north winds Sunday and
Monday. 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:
 -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.
 -10-25% 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: 30-50%, highest along and west of I-5 in the
  Sacramento Valley.
 --Monday: 20-40% across the central/southern 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 Valley and Delta.

* Tuesday - Thursday:
 -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
  very dry conditions prevail.
 -Elevated fire weather conditions anticipated.

.Changes from previous forecast...
 -Moderate HeatRisk and elevated fire weather conditions looking
  to persist into the late week period.

&&

.AVIATION...
VFR conditions expected to prevail over Valley TAF sites next 24
hours. Surface winds will increase in response to a upper level
trough moving into the Great Basin. For sites in the Northern
Sacramento Valley; surface winds from the north around 15 knots,
gusting 25-30 knots beginning around 12z Saturday. Onshore flow in
the Central/Southern Sacramento Valley, Delta, Northern San
Joaquin Valley`s increase to around 20 knots, gusting to 30 knots
around 10z Saturday. Over the western Sierra slope, surface winds
gusting up to 40 knots beginning around 12z tomorrow.

&&

.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.

&&

$$