Arnold, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

071
FXUS66 KSTO 292019
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
119 PM PDT Sun Jun 29 2025

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

.DISCUSSION...

.SYNOPSIS...
Warm and dry weather continues this week with periodically breezy
onshore winds. Widespread Moderate HeatRisk persists into the
middle of next week. Mountain thunderstorm chances return next
week. Lightning on dry fuels may lead to easier fire starts early
next week.

&&

.KEY MESSAGES...

* Today:
 -Continued warm temperatures across the area, with highs in the
  upper 90s to around 106; higher temperatures in the northern
  Sacramento Valley.
 -Widespread Moderate HeatRisk across interior NorCal
 -Probability of Valley high temperatures > 100F:
  Northern Sacramento Valley: 75-100% Elsewhere: around 20-40%
 -A non-zero (5-10%) chance of an afternoon/evening shower or
  isolated t-storm along the Sierra crest. Confidence low on
  development, best forcing mechanisms remain off shore and to
  the east of Sierra crest.

* Early to Mid Week:
 -Above normal temperatures persist this week with Moderate
  HeatRisk, although increased onshore flow brings some relief to
  the Delta vicinity Monday-Tuesday
 -Slight (10-20%) probability of thunderstorms early to mid next
  week during the afternoon and early evening hours across the
  mountains of interior NorCal. Highest thunderstorm probabilities
  over the northern mountains on Monday-Tuesday. Thunderstorm
  chances expand farther south into the Sierra by Wednesday.
 -Lightning on dry fuels may lead to easier fire starts. A Red
  Flag Warning has been issued for the northern Coast Range,
  Shasta County mountains and Burney Basin from 11 AM - 8 PM
  Tuesday.

* Later This Week:
 -Slight cooling trend with Minor HeatRisk returning to interior
  NorCal
 -Potential for mountain thunderstorm chances (10-20%) persisting
  through late week.

.Changes from previous forecast...
 -Fire Weather Watch has been upgraded to a Red Flag Warning for
  lightning on dry fuels for the northern Coast Range, Shasta
  County mountains and Burney Basin from 11 AM to 8 PM Tuesday.
  Slight areal expansion of the warning (fire zones 266 and 268
  within Shasta County), along with a temporal extension (now runs
  through Tuesday, July 1 at 8 PM PDT).

&&

.AVIATION...

VFR conditions prevail across interior NorCal next 24 hours.
Surface winds 12 kts or less, except in the Delta vicinity where
southwest gusts 20 to 25 kts are expected through 06Z Monday.
Isolated mountain thunderstorms possible across northern
Sacramento Valley and surrounding terrain after 18z Monday.
&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM Monday to 8 PM PDT Tuesday for
Burney Basin and Northeast Plateau in Shasta County Including
Northwest Lassen NF north of Lassen NP-Eastern Mendocino NF-
Eastern Portion of Shasta/Trinity NF-Northern Sierra Foothills
from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and
Butte Units-Northern Sierra Including Lassen NP and Plumas and
Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly
Peak-Beckworth Peak)-Southeast Edge Shasta-Trinity NF and
Western Portions of Tehama-Glenn Unit.

&&

$$