237
FXUS66 KSTO 181918
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1218 PM PDT Tue Aug 18 2026


.KEY MESSAGES...

  - Elevated Fire Weather Conditions Friday through Saturday within
    the Burney Basin due to low RH and breezy westerly winds.

  - Dry and seasonably warm through the week and into the weekend.

&&

.DISCUSSION...

Current synoptic pattern aloft has a ridge of high pressure across
the four corners of the United States, with southwesterly flow
over California. Satellite/observations have sunny conditions
this afternoon, with temperatures hovering in the 80s to lower
90s. Highs will be in the 90s today within the Valley and portions
of the foothills, with lower 100s in the northern Sacramento
Valley. Cooler conditions as you head further into the mountains.
Warmest conditions are expected today through Friday, but trend
cooler over the weekend and into next week. A weak trough moves
along the ridge Thursday and Friday bringing lift to portions of
northern California. Looking at soundings, we have weak synoptic
support, little moisture content, and lacking instability to
develop chances for showers and storms. Instability is slightly
higher toward the Shasta-Trinity area and there is a very low
chance (less than 5 percent) for a quick storm to develop in the
afternoon/evening hours both Thursday and Friday. None the
less, there will be enough forcing to bring clouds to Interior
Northern California Thursday through Friday.

As the system moves through the region, winds become breezy
through the Delta and into the Burney Basin. Delta winds gust up
to 20kts during the evening hours helping to cool off temperatures
and increase RH values. In the Burney Basin the already dry RH
values in the upper teens to mid 20s range combined with breezy
downsloping westerlies bring elevated fire weather concerns both
Friday and Saturday. We will continue to monitor the fire weather
conditions for the Burney Basin end of the week and into the
weekend. Otherwise, looking behind the weekend conditions look to
remain dry as the ridge remains locked into place.
&&

.AVIATION...

VFR conditions continue through the TAF period, with breezy
onshore winds within the Delta and portions of the Sacramento
Metro this evening. A few gusts to 20kts in the Delta this
evening. SCT to BKN clouds move in around 04-08z and continue
through 18z for the Sacramento sites, MOD, and SCK.

&&

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

&&

$$