646
FXUS66 KSTO 191939
AFDSTO
Area Forecast Discussion
National Weather Service Sacramento CA
1239 PM PDT Fri Jun 19 2026
For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.
.KEY MESSAGES...
- Scattered wet and dry thunderstorms will result in critical
fire weather conditions in Shasta County today.
- Elevated fire weather concerns elsewhere in the mountains north
of I-80 due to isolated showers and thunderstorms.
- Warming trend next week with minor to moderate HeatRisk.
&&
.DISCUSSION...
Current satellite and radar has reflectivity over the northern
portions of the CWA in Shasta, Glenn, Tehama, Butte, and Plumas
counties. Observations across the area have some precipitation
reaching the surface while in other regions it is not. We have
seen reports of dry thunderstorms at times around Shasta county
over the past couple of hours. CAMS have continued to show the
main area of forcing moving further into the higher terrain as we
move into the afternoon hours. Atmospheric soundings around Shasta
County and into the southern Cascades have continued to show
inverted V structures in the lower levels for parts of the higher
turns, with only slight disagreements between models. Instability
and lift start to dwindle in the evening hours, with the threat
for thunderstorms dropping. Areas that experience the wet
thunderstorms could see up to a quarter of an inch for rainfall.
Lightning from the isolated dry thunderstorms or outside the main
precipitation cores in wet thunderstorms could create new fire
starts and may combine with strong outflow winds to cause a fire
to rapidly row. Our confidence is low on the coverage and wet vs
dry for thunderstorms. None the less, Shasta county remains in a
Red Flag Warning for critical fire weather conditions due to the
scattered dry thunderstorms. Other areas see elevated fire weather
concerns in the mountains north of I-80 where dry thunderstorm
chances are isolated. A few storms this afternoon could be on the
stronger side, bringing small hail and gusty outflow winds.
The main shortwave providing the support for thunderstorm
activity continues to move east across CA and into the Great Basin
Saturday. Lingering instability and moisture will help fuel
further chances for isolated thunderstorms around Shasta county
tomorrow afternoon and into parts of the evening hours. Confidence
is low on the coverage, the chance for isolated dry
thunderstorms, and how far south the instability reaches into
Shasta county. Elevated fire weather conditions are expected
around Shasta county tomorrow due to the threat of isolated
thunderstorms.
The upper level pattern begins to shift, and we introduce high
pressure into the area Sunday and into next week. Temperatures
warm and conditions dry out with low RH values within portions of
the Valley. Winds at this time have remained on the lower side,
but we will continue to monitor any chances for fire weather
conditions next week.
&&
.AVIATION...
VFR conditions are expected to continue through the TAF period.
There will continue to be a chance for an isolated shower or
thunderstorm around RDD and RBL through 23z this afternoon.
Otherwise, areas are seeing SKC to FEW cloud coverage. Winds from
the Delta will increase for the Sacramento sites this evening and
into the early overnight, with gusts up to 20kts. Winds overnight
go light and variable for the sites.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM PDT this evening for Burney Basin-E.
Shasta /S. Cascades Above 3000 ft-Shasta County Foothills 1000-
3000 ft-Shasta Lake Area & 1-5 1000-3000 ft-Shasta Metro-W.
Shasta County 1000-3000 ft-W. Shasta County Above 3000 ft.
&&
$$
