001
FXUS66 KSTO 051035
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
335 AM PDT Fri Jul 5 2024

.SYNOPSIS...
Widespread Major to Extreme HeatRisk through early next week.
Elevated fire weather concerns in the Valley and adjacent
foothills through early next week due to very hot and dry
conditions. Slow downward trend in high temperatures next week,
but temperatures will remain hot.

&&

Key Points
- Long-duration, dangerous heat event through early next week,
  impacting holiday outdoor events.
- 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 from 11 AM today until 11 PM Tuesday.

.Discussion...
A dangerous, long-duration heat event persists across the region
given anomalously strong high pressure. Today and Saturday are
forecast to be the hottest days of the heat event, with highs
climbing into the 105-118 degree range in the Valley, Delta, and
foothills. NBM probabilistic guidance indicates a 60-100% chance
of highs greater than 110 deg F across the northern and central
Sacramento Valley, with a 20-60% chance across the southern
Sacramento and northern San Joaquin Valleys. Overnight
temperatures will provide little to no relief from the heat with
lows ranging from the upper 60s to mid 80s; warmest in the thermal
belt regions of the foothills.

Widespread Major to Extreme HeatRisk is expected across the
Valley and foothills, with Major HeatRisk over the mountains.
This level of rare, long-duration extreme heat with little to no
overnight relief affects anyone without effective cooling and/or
adequate hydration. 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 until 11 PM Tuesday. Check on
sensitive groups, stay hydrated, strongly consider canceling
outdoor activities, and stay in a cool place, including overnight.
DO NOT leave children or pets in unattended vehicles.

Ensembles show a mid to surface level coastal trough developing
late weekend into early next week, suggesting a possible return of
the Delta Breeze. This may allow for some relief for Delta Breeze
influenced areas, with widespread Moderate HeatRisk forecast by
early next week. Elsewhere, Major to Extreme HeatRisk is
anticipated. By Monday, Valley daytime temperatures are still
expected to range from 100-112 deg F. Some overnight relief is
expected in the Delta and southern Sacramento Valley, with low
temperatures in the 60s.

The extended period of very hot and dry conditions, along with
periods of breezy winds at times, will bring elevated fire weather
concerns to the Valley and foothills. Minimum relative humidity
values will be in single digits to teens, with moderate to poor
overnight humidity recoveries over the foothills and northern
Sacramento Valley. Know your wildfire risk and have an emergency
plan in advance.

&&

.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...
Ensembles and clusters show an eastward progression and weakening
of the upper high. This will allow for the return of some weak
onshore flow, resulting in a slow downward cooling trend next
week. HeatRisk will be in the Moderate category for most of the
Valley and Delta, with areas of Major and Extreme HeatRisk
prevailing across portions of the northern Sacramento Valley and
foothills. Valley highs are expected to range from 100-110 deg F.
Some overnight relief from the heat will be possible near the
Delta Breeze influenced areas. Low temperatures into the upper 50s
to mid 60s will be possible in these areas, with upper 60s to mid
70s still likely through the remaining Valley and adjacent
foothills locations.

Elevated fire weather concerns are expected for the Valley and
foothills given hot temperatures, dry conditions, and breezy
afternoon winds at times.

&&

.AVIATION...
VFR conditions expected across interior NorCal next 24 hours.
Breezy south to west gusts 10 to 20 kts in Delta and immediate
vicinity through 00Z Friday before slowly tapering off to around
10 kts by 12z Friday.

&&

.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.

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

&&

$$