Castella, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

613
FXUS66 KSTO 091952
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1252 PM PDT Fri May 9 2025

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

.Discussion...

.Synopsis...
Dry and seasonably warm weather continues into the weekend, as
well above normal high temperatures peak today and Saturday.
Widespread Minor HeatRisk and areas of Moderate HeatRisk are
anticipated as a result. A pattern change to cooler and unsettled
weather is expected moving into early next week. Elevated fire
weather conditions on Sunday will then be followed by chances for
rain/mountain snow showers and isolated thunderstorms across
interior NorCal Monday and Tuesday.

&&

.Key Messages...

* Today - Saturday:
 -Periodic late day breezy onshore winds.
 -Dry and warm weather with temperatures 10-15 degrees above
  normal under upper level ridging, peaking today and Saturday.
 -Areas of Moderate HeatRisk across the Central Valley Today &
  Saturday. Probability of high temperatures 90 degrees F or
  higher: 60-90% throughout the Valley Today & Saturday.

* Sunday - Tuesday:
 -A trend toward cooler and more unsettled weather is expected,
  with a weather system arriving Sunday into early next week.
 -Gusty southerly winds Sunday, remaining breezy Monday and
  Tuesday. Probability of gusts 40 mph or higher: 40-70% northern
  and western Sacramento Valley, and northeast foothills on Sunday.
 -Elevated Fire Weather conditions Sunday as gusty winds and low
  RH overlap, particularly across the northern/central Sacramento
  Valley.
 -Rain and mountain snow chances expected as the system moves
  through.
 --48-Hour Probability of Rain > 0.25": 50-80% across northern
  Sacramento Valley, Sierra north of Hwy 50, and adjacent
  foothills. 5-15% remaining Valley locations, Delta, and
  foothills.
 --Isolated Thunderstorm Probability: 15-30% Monday and Tuesday,
  highest across north/central Sacramento Valley and along higher
  terrain.
 -- 48-Hour Probability of Snowfall > 4": 20-50% along
  Sierra/southern Cascades above 6000 feet.

* Mid to Late Next Week:
 -Progressive west-northwesterly flow aloft expected.
 -Generally dry weather, with temperatures warming to near normal.

.Changes from previous forecast...
 -Elevated fire weather conditions becoming more likely Sunday
  afternoon.
 -Slight increase in isolated thunderstorm chances on both Monday
  and Tuesday.

&&

.AVIATION...
VFR conditions expected across all TAF sites in the Sacramento
Valley next 24 hours. Diurnal surface winds less than 12 knots for
the Valley. Onshore flow in the Delta with surface winds gusting
up to around 15 knots. In the mountains, terrain driven winds with
gusts up to 25 knots through 06z Saturday.

&&

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

$$