Afton, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

690
FXUS66 KSTO 192115
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
215 PM PDT Thu Jun 19 2025

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

.DISCUSSION...

.SYNOPSIS...
Seasonable high temperatures with enhanced onshore flow today and
tomorrow. Elevated fire weather conditions in the northern and
central Sacramento Valley today and tomorrow from breezy west-
southwest winds and low daytime humidities around 10-25%. This
weekend, a mainly dry weather system builds north of the area and
bring slight (5%) chances of light showers in northern Shasta
County and southern Cascades Friday PM - Saturday AM. As system
moves through, winds will begin to shift from the north on
Saturday and Sunday morning, introducing periods of critical fire
weather in the Valley, Coastal Range, and northern San Joaquin
Valley.

&&

.KEY MESSAGES...

* Today:

 -Combination of warm weather with dry conditions may bring a
  brief period of locally elevated fire weather conditions, mainly
  across the northern and central Sacramento Valley.

 -Please continue to practice heat and fire safety such as ,
  avoiding activities during the heat of the day, properly
  extinguishing any campfires, and not driving over dry grass.

*Friday-This Weekend:

 -Gradual cooling trend expected with stronger onshore flow Friday.
  Strongest winds expected through the Delta and over the Sierra.
  South to west forecasted shifting to north to west winds over
  the weekend.

 -Elevated fire weather conditions expected across the Sacramento
  Valley tomorrow due a combination of low humidity and locally
  breezy winds, particularly across the northern Sacramento and
  northern San Joaquin Valleys.

 -Critical fire weather conditions expected across the Sacramento
  Valley, Coastal Range, and northern San Joaquin Valley Saturday
  AM - Sunday AM. Latest forecast runs have increased wind gusts
  in the aforementioned areas, along with lower daytime humidity
  values around 15-25%, and north wind gusts 30-40 mph. A Fire
  Weather Watch has been issued for most of the Sacramento Valley
  and northern San Joaquin Valley Saturday AM - Sunday AM.

 -Min RH values in the teens to low 20s Friday - Sunday across
  the northern Sacramento Valley, Valley Foothills, and Northern
  San Joaquin areas

 -Probability of wind gusts > 30 mph:
*60-95% Friday across the Northern/Central Sacramento Valley
*60-90% Saturday across the Sacramento Valley and Delta.

 -Isolated showers over northern Shasta County and Southern
  Cascades Friday into Saturday morning but little to no impacts
  expected.

* Next Week:

 -Dry conditions with a warming trend as we move into the middle
  of next week. Broad zonal flow will allow onshore winds to
  continue in the Delta and adjacent areas. Stagnate flow
  elsewhere will allow temperatures to begin to climb into the
  upper 90s and triple digits by Wednesday in the northern
  Sacramento Valley. Minor HeatRisk is expected at this time,
  thanks to Delta Breeze helping improve overnight relief with low
  temps in the mid 50s to mid 60s in the Valley/Delta.

.Changes from previous forecast...
 -Fire Weather Watch issued for most of the Sacramento Valley,
  Coastal Range, and northern San Joaquin Valley beginning
  Saturday morning through Sunday morning. North winds of 10-20
  mph, with gusts 30-40 mph and daytime humidity values in the
  15-25% range will allow critical fire weather conditions to
  develop.

&&

.AVIATION...

VFR conditions continue at TAF sites over the next 24 hours.
Gusty west to southwest wind gusts around 15-30 kts across
interior NorCal until around 12z Thursday and again after 18z
Friday. Strongest winds are expected through the Delta and
vicinity and over the mountains.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday morning through Sunday morning
for Carquinez Strait and Delta-Central Sacramento Valley in
Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below
1000 Ft-Eastern Mendocino NF-Northern Sacramento Valley to
Southern Tehama County Line Below 1000 Ft-Northern San Joaquin
Valley in San Joaquin and Stanislaus Counties Below 1000 ft-
Northern Sierra Foothills from 1000 to 3000 Ft. Includes
portions of Shasta-Trinity and Butte Units-Southeast Edge Shasta-
Trinity NF and Western Portions of Tehama-Glenn Unit-Southern
Motherlode From 1000 to 3000 Ft. Includes portions of Calaveras-
Tuolumne Unit-Southern Sacramento Valley in Yolo-Sacramento Far
Western Placer, southern Sutter and Solano County Below 1000 Ft.

&&

$$