Vacaville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

006
FXUS66 KSTO 122018
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
118 PM PDT Tue Aug 12 2025

.DISCUSSION...

.SYNOPSIS...
Areas of Moderate HeatRisk with triple digit highs in the Northern
Sac. Valley this afternoon ahead of a cooling trend for the
remainder of the week. Non-zero chance of isolated mountain
showers and thunderstorms this afternoon, south of Interstate 80.

&&

.KEY MESSAGES...

*Today:
 - Areas of Moderate HeatRisk today over the Northern/Central
   Sacramento Valley and adjacent foothills;Cooling trend
   elsewhere
 - Probability of high temperatures > 100F:
    -Northern Sacramento Valley: 70-95%
 - Afternoon highs in the mid 90s to mid 100s with dry conditions
   over the Northern Sac Valley (Min RHs - 15-25%)
 - Non-zero chance of isolated mountain thunderstorms mainly south
   of Interstate 80 if anything does develop

*Wednesday-Friday:
 - The East Pacific ridge axis aloft weakens as an upper trough
   from western Canada drops down bringing increased onshore flow,
   cooler temperatures, and higher relative humidity
 - The increased Delta breeze will give noticeable relief for the
   Delta and southern Sacramento Valley by Wednesday morning
 - Afternoon highs cooling to upper 80s to upper 90s this week

*Weekend:
 - Near to below average temperatures then continue later this
   week and into the weekend with rising relative humidity
 - Periodically breezy onshore flow is forecast at times,
   strongest in the Delta vicinity and over the Sierra Crest
 - Low confidence in isolated thunderstorm potential along the
   higher elevations in the mountains this weekend (10-15% chance),
   dry weather elsewhere

.Changes from previous forecast...
- No significant changes to the forecast at this time.

&&

.AVIATION...

VFR conditions continue the next 24 hours over interior NorCal.
Surface winds generally below 12 knots, with a brief period from
around 22z today through 16z Wednesday with west-southwest
surface winds gusting up to 30 knots in the Delta and southern
Sacramento Valley.

&&

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

$$