517
FXUS66 KSTO 101932
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1232 PM PDT Fri Jul 10 2026

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


.KEY MESSAGES...

 - Near to above-normal temperatures and areas of Moderate
   HeatRisk into next week, with continued onshore flow
   moderating overnight temperatures.

 - Breezy southerly winds and marginally low daytime humidity will
   bring elevated fire weather conditions today.

 - Monsoonal moisture to bring showers and thunderstorms to the
   Sierra early next week.

&&

.DISCUSSION...
Mostly clear skies this afternoon across NorCal, accompanied by
locally breezy southerly winds in the Sacramento Valley. Weak high
pressure to the south and off-shore troughing are continuing to
keep upper level heights across NorCal more zonal. Valley &
foothill southerly winds and marginally low daytime humidity
values are leading to slightly elevated fire weather conditions
today. Fire weather conditions will improve as we move into the
overnight hours as the main driving factor, the winds, begin to
weaken later tonight. The start of the weekend will see high
pressure begin to move eastward and into the greater Four Corners
region, while amplified troughing remains offshore. Ridge will
strengthen by Sunday, allowing for a gradual climb in afternoon
high temperatures with areas of Moderate HeatRisk Saturday and
Sunday.

Ridge moves further north and east by Sunday, with offshore
troughing remaining in place, which will allow for monsoonal
moisture surges into the area Sunday through at least the middle
of next week. 500mb vorticity suggests several shortwave shots of
energy moving onshore Sunday afternoon and evening, potentially
tapping into the monsoonal flow to bring mainly cloud coverage
and/or virga to the Valley and foothills. More robust moisture
surge and upper-level synoptic support arrives late Sunday
night/early Monday morning, where slight chances of Valley
sprinkles have been introduced to the forecast. Better support for
convection will remain in the higher elevations in the Sierra and
south of I-80, however precipitation and/or t-storms cannot be
ruled out along most of the Sierra Nevada as we push into Monday
afternoon and evening.

While confidence has increased in monsoonal moisture surges,
enough instability in the area remains the biggest question on
t-storm development for lower elevations in the foothills.
Forecast soundings do show inverted-v profiles, however lack of
instability in the lower levels may prevent convection from
developing. Latest NBM runs have introduced slight (15%) chance of
thunderstorms to around 3000 feet along the Sierra Monday
afternoon and evening. Uncertainty remains high on the lower
elevation development, and for that reason we have decided to hold
off on any fire weather products at this time.

Monsoonal moisture will continue to push through our higher
elevations along the Sierra Tuesday-Thursday, where a roughly
15-30% chance of afternoon/evening thunderstorm will exist, with
the best probabilities along and east of the Sierra crest. Best
chances will remain mainly south of I-80. With warmer temperatures
continuing, fuels will start to dry out, so fire weather
concerns will continue Tuesday through Thursday. Widespread
Moderate HeatRisk enters the forecast Tuesday and Wednesday,
before widespread Minor HeatRisk takes over Thursday with
slightly cooler afternoon high temperatures.

&&

.AVIATION...

VFR conditions prevail across interior NorCal next 24 hours.
Surface winds from south to southwest around 15 to 25 kts in the
Sacramento Valley. Surface winds around 15 to 20 kts in northern
San Joaquin Valley. Gusts everywhere except the Delta decrease to
12 kts or less around 09z Saturday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$