091
FXUS66 KSTO 221825
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1125 AM PDT Fri May 22 2026

.KEY MESSAGES...

 - Above-normal temperatures today with isolated mountain showers
   and thunderstorms.

 - Cooling trend through the weekend and into early next week.

 - Increased onshore flow through the holiday weekend, combined
   with low daytime RHs, will lead to elevated fire weather
   conditions in the Valley.

 - Winds switch, becoming gusty and out of the north around
   Tuesday, with continued elevated fire weather conditions.

&&

.DISCUSSION...

...Today to Saturday...
GOES-West visible satellite imagery reveals a cloudless Central
Valley with some cumulus beginning to bubble-up over the northern
Sierra. Synoptically we currently find ourselves nudged between a
sagging trough over the Rocky Mountains and a broad, flat ridge
over the northern Pacific. The net result for northern California
will be another warm afternoon with temperatures around 10 deg F
above late-May climatology, as well as isolated mountain showers
and thunderstorms for the afternoon. The latest National Blend of
Models (NBM) guidance advertises around a 15-25% chance of thunder
for the Sierra as well as a 10-15% chance along the Coastal
Range. A healthy Delta breeze is forecast to develop this
afternoon with the onshore gradients, and will make for a pleasant
Friday evening for Solano, Yolo, Sacramento, San Joaquin and
Stanislaus Counties.

For Saturday, temperatures start to become noticeably cooler for
southern Sacramento Valley, northern San Joaquin Valley, and Delta
communities as the continued onshore flow influences the max
temps. While cooling is expected elsewhere, such as the northern
Sacramento Valley, the day-to-day difference is not forecast to be
as notable. The onshore flow will continue, and combined with
minimum RHs around 18-25%, will result in brief periods of
elevated fire weather concerns, particularly in Valley locations
away from the Delta where the marine-influenced RHs aren`t
realized. Please do be mindful of any holiday weekend activities
that involve fire/flame; the fuels will only continue to dry as
we dive into the dry season. // Rowe

...Sunday to Thursday...
Similar conditions are forecast for the region on Sunday with
breezy onshore west/southwest winds as weak troughing develops
along the California coast. This will maintain the elevated fire
weather concerns through Sunday and into the holiday on Monday.
From Monday to Tuesday, an upper-level low will dive south from
the Gulf of Alaska toward the Pacific Northwest, then push inland
over Oregon by late Tuesday. While the exact details on the low`s
trajectory are still to be determined, this pattern setup would
result in offshore northerly winds for NorCal, as well as fire
weather concerns. Depending on how much moisture accompanies the
low, can`t rule out the chance of some mountain convection, as
well. // Rowe

&&

.AVIATION...
VFR conditions are expected over the next 24 hours. West-
southwesterly winds increase after 20Z Friday in the
Delta/Sacramento Valley, with north-northwesterly winds in the
northern San Joaquin. Valley gusts 15 to 20 kts until 12Z
Saturday. Stronger gusts in the Delta up to 25 kts through 18Z
Saturday.

&&

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

&&

$$