001
FXUS66 KSTO 182010
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
110 PM PDT Thu Jun 18 2026

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


.KEY MESSAGES...

 - Cooler and more seasonable weather through Saturday before a
   return to hot and dry conditions Sunday through next week.

 - Elevated fire weather conditions are anticipated due to the
   potential for elevated mountain thunderstorms and gusty
   thunderstorm outflow winds.

&&

.DISCUSSION...

Conditions across the area this afternoon show mostly sunny skies
with temperatures in the 80s to mid 90s for daytime highs. Warmest
temperatures are expected in the northern Sacramento Valley. Upper
level pattern has a weak shortwave moving along the California
coast and shifting inland through the early part of the weekend.
Moisture influx and instability increase as the shortwave moves
onshore. HIRES guidance has indicated the potential for isolated
thunderstorm activity within the Sierra for this afternoon and
evening (along and south of I80), with soundings indicating
modest moisture in the low levels along and west of the crest.
There is a potential for a few isolated dry thunderstorms mainly
in the Sierra and along the crest this afternoon/evening.
Probabilities are 20 percent for occurrence as the soundings
indicate sufficient moisture content. None the less, this brings
the elevated fire weather concerns for today.

Chances for continued isolated showers and thunderstorms overnight
and into Friday, with coverage increasing along the northern and
northeastern section of the forecast area Friday morning. This
would include the southern Cascades into portions of the coastal
range near Shasta county. As the center of shortwave moves
onshore, initiation of thunderstorms start in the southern
Cascades and coastal range through Shasta county. Some dry air is
noted in the latest HIRES atmospheric soundings showing slight
inverted V structures at times. Elevated fire weather concerns
are anticipated from isolated to scattered dry thunderstorms
during the morning and afternoon hours on Friday. Main threats
from the dry thunderstorms would be new fire starts and gusty
outflow winds.

Uncertainty arises with the coverage of the dry thunderstorms and
how much dry air is near the surface through 700mb. As of right
now the probabilities of thunderstorms is around 30 percent with
the highest in the southern Cascades. This is where the CAMS have
picked up the highest chances for initiation of thunderstorms as
the short wave moves onshore. Because of the uncertainty in
coverage and nature of thunderstorms, we do not anticipated the
need for a Red Flag Warning at this time. We will continue to
monitor the latest trends and if the need arises for the increased
messaging for fire weather concerns.

Around the mid to late afternoon hours, chances for storms begin
to dwindle as the wave moves further east. Concerns for fire
weather start to dwindle by the evening and overnight hours.

Moving into the weekend and beyond we will start to heat back up
into the 90s across the area, with the potential for lower 100s as
we move into the new work week. Conditions will start to dry out
quickly and RH values begin to drop. Confidence is increasing in
the potential for breezy conditions at times next week on top of
the drier conditions. We will continue to monitor the fire weather
conditions for next week.

&&

.AVIATION...

VFR conditions are expected through the TAF period. Winds are
light and variable, but increase out of the west for the
Sacramento sites this afternoon and evening. Sustained winds up to
15kts are possible. Periods of gusts of 20-25kts for Sacramento
sites this evening. RDD and RBL will see southerly winds this
afternoon and evening, while SCK and MOD see WNW to NW winds.
Winds do go light and variable overnight and into tomorrow
morning. Otherwise, higher terrain isolated showers and
thunderstorms will be possible this afternoon and evening.

&&

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

&&

$$