Rio Oso, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

062
FXUS66 KSTO 091943
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1243 PM PDT Mon Jun 9 2025

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

.DISCUSSION...

.SYNOPSIS...
Isolated shower/thunderstorm chances over higher terrain persist
today and Tuesday primarily north of Interstate 80 as the split
flow regime aloft begins to deteriorate. Broad zonal flow is then
expected to set up across interior NorCal through the remainder of
the week, with troughing arriving into next weekend. As a result,
an overall stagnating weather pattern of predominantly dry
weather, near normal temperatures, and breezy onshore flow looks
to persist.

&&

.KEY MESSAGES...

* Heat Advisory in effect through 11 PM PDT tonight for portions
  of the northern Sacramento Valley and adjacent mountains/foothills.

* Today-Tuesday:

 -Widespread Moderate HeatRisk across interior NorCal and areas of
  Major HeatRisk across the northern Sacramento Valley today, dissipating
  to areas of Moderate HeatRisk by Tuesday.

 --Probability of Valley High Temperatures > 95F:
  ---Northern/Central Sacramento Valley: 80-100% Today, 60-90%
   Tuesday
  ---Delta, S. Sacramento Valley, N. San Joaquin Valley: 20-50% Today
   & Tuesday

 --Probability of Valley High Temperatures > 100F:
  ---Northern/Central Sacramento Valley: 60-90%, Today

 -Periodically breezy onshore flow, strongest in the Delta and
  vicinity during the afternoons and evenings.

 -Chances for isolated afternoon/early evening showers and
  thunderstorms:
    --Today: 15-30%, across Sierra/southern Cascades north of
     Interstate 80 and northern Sacramento Valley and surrounding
     terrain.
    --Tuesday: 5-15%, across Shasta County mountains

* Wednesday-Sunday:

 -Gradual cooling trend expected through the remainder of the
  week. Primarily Minor HeatRisk as temperatures become more
  seasonable.

 -Probability of Valley High Temperatures > 90F:
  --Northern/Central Sacramento Valley: 60-90% Wed-Thu, 30-50%
   Fri-Sun
  --Delta, S. Sacramento Valley, N. San Joaquin Valley: 50-80%
   Wed-Thu, 20-40% Fri-Sun

 -Onshore flow expected to persist with periods of breezy winds,
  mainly in the afternoons and evenings and strongest across the
  Delta and vicinity.

 -Ensemble uncertainty in a trough digging southward from the Gulf
  of Alaska next weekend persists. Current trends indicate a
  continuation of seasonable and breezy weather anticipated at
  this time.

.Changes from previous forecast...
 -No notable forecast changes since last update.

&&

.AVIATION...
VFR conditions expected at Valley TAF sites next 24 hours, with
possible MVFR/IFR conditions in isolated mountain and foothill
t-storms from around 20z today through 05z Tuesday. Mostly onshore
flow in the Valley/Delta, with surface winds at or below 15
knots. Period of gustier surface winds from around 21z through 16z
Tuesday, with surface gusts up to 25 knots possible.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 11 PM PDT this evening for Northern
Sacramento Valley-Shasta Lake Area / Northern Shasta County.

&&

$$