592
FXUS66 KSTO 022111
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
211 PM PDT Tue Jul 2 2024



.SYNOPSIS...
Widespread Major to Extreme HeatRisk into next week. Critical
fire weather conditions in the Sacramento Valley and adjacent
foothills through Wednesday.

&&

Key Points
- Long-duration, major heat event into next week, impacting
  holiday outdoor events.
- Red Flag Warning is in effect for much of the Sacramento Valley
  and adjacent elevations below 3000 feet through Wednesday
  evening.
- Excessive Heat Warning remains in effect for the Valley, Delta
  and foothills through 11 PM Tuesday.
- Heat Advisory goes into effect tomorrow at 11 AM for the
  mountains and higher elevations in the Sierra until 11 PM
  Tuesday.

.Discussion...
Clear skies are being observed overhead, alongside breezy
northerly winds and lowering relative humidities through the
Sacramento Valley. Across the western half of the Sacramento
Valley, gusts 20 to 30 mph are being observed as of 1:45 PM with
relative humidities in the 10-15% range. Gusty winds up to 30 mph and
low relative humidities (5 to 15%) will continue through
Wednesday, coupled with poor overnight recovery (max RH 15-35%).
As a result, a Red Flag Warning is in effect for much of the
Sacramento Valley and surrounding foothills below 3000 ft until 8
PM Wednesday.

As a strong area of high pressure just offshore of the Pacific
Northwest inches ever closer onshore, resulting in increasing
temperatures throughout interior NorCal into next week. This long-
duration major heat event will bring elevated high temperatures
and above-normal overnight low temperatures, especially where
thermal belts are present in the foothills. Highs of 105 to 118
are expected in the Valley & foothills, and in the mountains high
temperatures up to 95-110 are expected. With little to no Delta
breeze influence this week, overnight lows in the Valley/foothills
will be in the upper 60s to mid 80s, and upper 50s to upper 70s
in the mountains resulting in very little overnight relief. The
hottest days of the week will be on Friday and Saturday. The
National Blend of Models (NBM) indicating a 70-100% chance of high
temperatures of 110 deg F or higher through the northern and
central Sacramento Valley, and a 50 to 75% chance in the southern
Sacramento and northern San Joaquin Valleys.

As a result, widespread major and areas of extreme HeatRisk are
present across the Valley & foothills, with areas of major to
extreme in the mountains. These levels of HeatRisk are VERY
DANGEROUS to anyone without proper hydration or adequate cooling.
Strongly reconsider any outdoor activities during this prolonged
heat event. DO NOT leave children or pets in unattended vehicles.
Car interiors will quickly reach lethal temperatures in a matter
of minutes.

An Excessive Heat Warning has been extended for the Valley &
foothills and will remain in effect through 11 PM Tuesday.
Additionally, a Heat Advisory will go into effect for the
mountains and higher elevations at 11 AM tomorrow until 11 PM
Tuesday.


&&


.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
Our prolonged heat event will continue into early next week with
swaths of Major to Extreme HeatRisk throughout our forecast area.
Guidance does hint at the Delta Breeze proving some limited relief
for the Delta and portions of the Southern Sacramento Valley this
weekend into early next week. The high pressure system residing
over California providing the heat continues over the area
although tilting eastward as a low pressure system moves into the
Pacific NW. On Tuesday, as the low pressure system moves further
into the Pacific NW, it begins the set up that opens the
possibility of further relief as some westerly flow may move over
the area later next week. Ultimately, the extended forecast looks
to be hot with highs 100+ degrees in the Valley, so people should
continue to exercise heat safety and be prepared to continue heat
mitigation actions into early next week.


&&


.AVIATION...
VFR conditions over interior NorCal next 24 hrs. In the Sac
Valley, areas of north winds 15 to 20 kts and southwesterly up to
15 kts in the vicinity of Delta through this afternoon before
Valley winds begin to taper off after 03z. Breezy north winds 10
to 20 kts return to the northern and western portions of the
Sacramento Valley 12Z tomorrow morning thru 21Z.


&&


.STO WATCHES/WARNINGS/ADVISORIES...
Excessive Heat Warning until 11 PM PDT Tuesday for Carquinez
Strait and Delta-Central Sacramento Valley-Motherlode-Mountains
Southwestern Shasta County to Western Colusa County-Northeast
Foothills/Sacramento Valley-Northern Sacramento Valley-Northern
San Joaquin Valley-Shasta Lake Area / Northern Shasta County-
Southern Sacramento Valley.

Red Flag Warning until 8 PM PDT Wednesday for Carquinez Strait
and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba,
Northern Sutter, and Butte County Below 1000 Ft-Eastern
Mendocino NF-Eastern Portion of Shasta/Trinity NF-Northern
Sacramento Valley to Southern Tehama County Line Below 1000 Ft-
Northern Sierra Foothills from 1000 to 3000 Ft. Includes
portions of Shasta-Trinity and Butte Units-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.

Heat Advisory from 11 AM Wednesday to 11 PM PDT Tuesday for
Burney Basin / Eastern Shasta County-West Slope Northern Sierra
Nevada-Western Plumas County/Lassen Park.

&&

$$