624
FXUS66 KSTO 172000
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
100 PM PDT Mon Jun 17 2024

.SYNOPSIS...
Critical fire weather conditions continue through early Tuesday
across the Valley and Delta from gusty northerly winds and low
minimum relative humidity. Dry and generally seasonable weather then
continues through midweek, with a warming trend expected late week
and through the weekend.

&&

Key Points
- A Red Flag Warning is in effect until 8 AM Tuesday across the
majority of the Delta region, Valley, and adjacent foothills  below
2000 ft, due to low daytime relative humidity, gusty  northerly
winds, and poor overnight recoveries.
- Generally seasonable temperatures continue through most of the
  week, with a gradual warming trend late week into the weekend.
- Widespread Moderate HeatRisk is expected from Friday through Monday,
  with some Major HeatRisk in the foothills on Saturday.

Short-Term Discussion (Today THROUGH Thursday)...
Dry and mostly clear conditions continue to prevail over the area
this afternoon. Already, relative humidities across the Valley
are starting to reach below 20%, with values forecasted to
potentially reach single digits locally in some areas. Winds, too,
have already gusted up to 37 mph at locations such as Red Bluff
and Stockton, with more gusty winds expected for the remainder of
today and into Tuesday. Ensembles show the trough causing these
critical fire weather conditions today through early Tuesday to be
moving eastward over the next couple of days. Until the low
pressure system moves out of the area however, it will continue to
bring breezy northerly winds and dry relative humidities to the
area. As such, a Red Flag Warning remains in effect for areas in
the Delta region and Valley below 2000 ft until 8 AM on Tuesday.

Late Tuesday and into Wednesday, as the current trough moves out
and a more broad troughing pattern covers the area, winds will
decrease and relative humidities will rise a little (though still
remaining in the 20-30% range in the daytime, and even lower in
the northern Sacramento Valley). Temperatures will remain near or
slightly below seasonable levels through Tuesday, though they
will begin to warm slowly mid-week, with Wednesday and Thursday
seeing Valley temperatures around the 90s, and upper 60s to upper
80s at higher elevations.

&&

.EXTENDED DISCUSSION (Friday THROUGH Monday)...
As we move into the weekend, weak broad troughing aloft is
suggested by ensembles and cluster analysis while a ridge of high
pressure will attempt to build in the Great Basin. Heights aloft
should continue to rise over our area in response, and lead to a
gradual warming trend Friday and Saturday. High temperatures on
Friday and Saturday are expected to be in the low 90s to around
105F across the Valley, with 70s to mid 80s for the Valley and
Foothills. Widespread Moderate HeatRisk will accompany both days,
with isolated areas of Major HeatRisk in the Foothills and
portions of the northern Sacramento Valley. On Sunday, heights
will lower slightly, which will bring slightly cooler air into the
area, although the cooldown will only be a few degrees.
Generally, still anticipating 90s to low triple digits (100-103)
in the Valley and 70s to low 80s in the Foothills and mountains.
The slight drop in afternoon temperatures will also bring
widespread Moderate HeatRisk on Sunday and Monday, with the Delta
and Sacramento areas in Minor HeatRisk as the Delta Breeze will
help keep things cooler in these areas.

&&

.AVIATION...
VFR conditions across interior NorCal for the next 24 hours. In
the Valley, widespread northerly surface winds up to 20 knots with
gusts 25-35 knots until around 03Z. In the Delta, winds shifting
westerly around 04Z with speeds of 5-15 knots. In the mountains,
expect surface winds from the northwest to northeast with gusts up
to 35 knots.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 AM PDT Tuesday for Carquinez Strait and
Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern
Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF-
Northern Sacramento Valley to Southern Tehama County Line Below
1000 Ft-Northern San Joaquin Valley in San Joaquin and
Stanislaus Counties Below 1000 ft-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-Southern Sacramento Valley in Yolo-
Sacramento Far Western Placer, southern Sutter and Solano County
Below 1000 Ft.

&&

$$