025
FXUS66 KSTO 032034
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
134 PM PDT Wed Jul 3 2024

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

&&

Key Points
- Long-duration, major heat event into mid 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 this evening.
- Excessive Heat Warning remains in effect for the Valley, Delta
  and foothills through 11 PM Tuesday.
- Heat Advisory remains in effect for the Sierra, southern
  Cascades, and Burney Basin now until 11 PM Tuesday.
- High likelihood of this heat continuing through mid next week

.Discussion...
Northerly wind gusts of 15-30 MPH continue across portions of the
western half of the Sacramento Valley and adjacent foothills
early this morning. Winds will begin to taper off later this
afternoon, becoming broadly light winds for the remainder of the
week. Given the ongoing combination of gusty winds and very low
humidities, our Red Flag Warning remains in effect for much of
the Sacramento Valley and surrounding foothills below 3000 ft
until 8 PM today. Even after the Red Flag Warning ends, very dry
weather with hot temperatures continue the threat of elevated
fire weather conditions this week into early next week.

Ensembles and clusters depict a strong, anomalous high pressure
remaining overhead through the forecast period. This will result
in a prolonged, dangerous heat event across the region. Daytime
temperatures will range from 104 to 118 degrees in the Valley and
adjacent foothills; peaking on Friday-Saturday. NBM probabilities
indicate a 75-100% chance of high temperatures of 110 deg F or
higher through the northern and central Sacramento Valley, and a
45 to 80% chance in the southern Sacramento and northern San
Joaquin Valleys. Little relief is expected overnight with lows
forecast in the upper 60s to mid 80s; warmest in the foothills.

As a result, widespread Major to Extreme HeatRisk is expected
across interior NorCal. This level of HeatRisk is 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 remains in effect for the
Valley, Delta, and foothills until 11 PM Tuesday. Additionally, a
Heat Advisory remains in effect for the Sierra, southern
Cascades, and Burney Basin from now until 11 PM Tuesday.

&&

.EXTENDED DISCUSSION (Sunday THROUGH Wednesday)...

Cluster analysis continues to indicate a gradual eastward
transition of the upper level ridge from the late weekend period
into next week. As this occurs, broad southwesterly flow should
begin to filter in aloft across interior NorCal. This will allow
for the return of at least some weak onshore flow to the region
into next week as well. Hot high temperatures of 108-114F are
still anticipated through Sunday afternoon in the Valley and
adjacent foothills, with a slight cool down closer to high
temperatures in the 102-110F range into mid next week.

Additionally, with increasing Delta breeze influence early next
week, some overnight relief from the heat will be possible,
particularly in the Delta vicinity and into the Sacramento metro.
Low temperatures into the low to mid 60s will be possible in these
areas through mid next week, with upper 60s to mid 70s still likely
through the remaining Valley and adjacent foothills locations. This
will correspond to widespread Major to Extreme HeatRisk on Sunday
for areas outside of the Delta vicinity and Sacramento metro.
HeatRisk values then remain largely the same through the early week
period, with a slight expansion of the Moderate risk area into the
northern San Joaquin and central Sacramento Valleys and throughout
the mountains.

&&

.AVIATION...

VFR conditions expected across interior NorCal next 24 hours. Breezy
northerly Sacramento Valley winds through 00z with occasional gusts
to 20 kts. Increasing south to west gusts to 20 kts in Delta and
immediate vicinity through 06z.

&&

.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 this evening 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 until 11 PM PDT Tuesday for Burney Basin / Eastern
Shasta County-West Slope Northern Sierra Nevada-Western Plumas
County/Lassen Park.

&&

$$