420
FXUS66 KSTO 232117
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
217 PM PDT Fri May 23 2025

.Discussion...

.Synopsis...
Mostly dry and periodically breezy weather expected from today
into early next week with temperatures fluctuating between near
and slightly above normal as a more progressive pattern sets up
aloft. Low, but nonzero, mountain thunderstorm chances Saturday,
otherwise, elevated fire weather conditions at times, especially
during breezier periods as low humidity and marginal recovery
persists. Trend toward well above normal temperatures anticipated
by late next week.

&&

.Key Messages...

* Today - Saturday:
 -Quick moving, shortwaves bring periods of breezy to briefly
  gusty onshore winds.
 -Probability of South-Southwest Wind Gusts > 30 mph:
  --Saturday: 40-70%, highest across Delta and vicinity area in
  afternoon/evening hours.
 -Marginal humidity recovery expected in onshore flow, although
  some localized areas of elevated fire weather conditions
  possible.
 -Temperatures to fluctuate around near to slightly above normal,
  with areas of Minor HeatRisk.
 -Slight, 5-10%, chance of isolated mountain showers/thunderstorms
  Saturday afternoon, primarily south of Interstate 80.

* Sunday - Monday:
 -Stronger weather system to progress toward interior NorCal
  Sunday-Monday.
 -Primarily dry weather anticipated, although a slight 5% chance
  of isolated showers/thunderstorms possible Sunday over the N.
  Sacramento Valley and Sierra.
 -Breezier onshore winds expected Sunday as the system arrives.
  Probability of South-Southwest Wind Gusts > 30 mph:
  --60-90% throughout the Valley and Delta on Sunday
 -Potential elevated fire weather conditions on Sunday with
  breezier winds expected.

* Tuesday - Friday:
 -Split flow aloft across interior NorCal as cutoff low settles in
  over SoCal.
 -Increasing heights aloft to introduce a persistent warming trend
  through much of next week.
 -Minor HeatRisk and areas of Moderate HeatRisk expected through
  Thursday, with some potential for Major HeatRisk in the Valley
  by Friday.
 -Probability of Valley high temperatures > 90F:
  --Tuesday-Thursday: 60-95%, highest Interstate 80 northward.
 -Probability of Valley high temperatures > 100F:
  --Friday: 30-75%, highest north of Interstate 80.

.Changes from previous forecast...
 -Slight mountain shower/thunderstorm chances Saturday
  afternoon/evening south of I-80.

&&

.AVIATION...

VFR conditions expected to prevail next 24 hours. Breezy westerly
wind gusts 15-20 kts vicinity Delta after 06z Friday. Otherwise,
surface winds less than 12 kts. Isolated showers or thunderstorms
over the Sierra 18z Sat - 00z Sunday, mainly from I-80 southward.

&&

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

$$