104
FXUS66 KSTO 052022
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
122 PM 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. Gradual cooling in high temperatures next week, but
temperatures will stay 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...
It`s going to be hot, hot, and then more hot as this dangerous,
long-duration heat event continues through early next week.
Saturday will be the hottest days of this heat event with
forecast highs of 105-118F. The NBM indicates a 80-100% chance of
high temperatures 110 deg F or higher across the northern and
central Sacramento Valley, and a 25 to 60% chance in the southern
Sacramento and northern San Joaquin Valleys today into Saturday.
Overnight temperatures will provide little to no relief from the
heat with lows in the upper 60s to mid 80s; warmest in the thermal
belt regions of the foothills. As a result, widespread Major with
areas of Extreme HeatRisk will be present across the Valley,
foothills, & mountains through the weekend.

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. It is
imperative for people to wear sunscreen, avoid the hottest part of
the day (10 am to 7 pm) and stay in the shade while outdoors. If
it`s too hot for you, it`s too hot for your pets. Make sure they
have ample access to water, shade, and ALWAYS look before you
LOCK. NEVER leave kids or pets in hot cars as temperatures will
become LETHAL in a matter of minutes.

A strong upper-level ridge will begin to weaken and gradually
slide southeastward towards the Great Basin by early next week
allowing for southwesterly flow aloft and weak troughing to
develop on the backend of the high. Temperatures will being to
cool slightly and weak, diurnal onshore flow returns to the region.
The National Blend of Models (NBM) indicates a 30 to 70% chance of
temperatures 105F or greater throughout the Valley, with 80 to
100% chance in the northern Sacramento Valley & foothills next
week.

The extended period of very hot and dry conditions will bring
elevated fire weather concerns to the Valley and foothills.
Minimum relative humidity values will be in single digits to
teens each day this week (15-25% near the Delta). Know your
wildfire risk and have an emergency plan in advance.


&&


.EXTENDED DISCUSSION (Tuesday THROUGH Friday)...
Ensemble guidance and cluster analysis support the continued
southeastward movement of the upper level ridge and development of
weak troughing on the backend. The cooling trend will continue
through next week. HeatRisk will be in the Moderate category for
most of the Valley and Delta, with areas of Major and Extreme
HeatRisk across portions of the northern Sacramento Valley and
foothills. Valley highs will range from 100-110 deg F with cooler
overnight lows in the upper 50 to mid 70s, with cooler
temperatures in the Delta. Additionally, occasionally breezy
afternoon onshore winds (15 to 25 mph) will contribute to an added
cooling effect, especially around the Delta where temperatures
will be several degrees cooler compared to more inland locations.
Despite this expected cooling trend, daytime relative humidities
will still be in the single digits to mid teens combined with hot
temperatures which will lead to elevated fire weather concerns
Valley and foothills.


&&


.AVIATION...
VFR conditions prevail next 24 hours across interior NorCal.
Generally light winds less than 12 kts expected for most areas.
Although increasing south to west winds are anticipated after 21z
in the Delta and vicinity, with occasional gusts to 20 kts
possible 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.

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

&&

$$