Heat in California, August 14 to 17, 2023

Area Forecast Discussion
National Weather Service Sacramento CA
222 AM PDT Mon Aug 14 2023

.SYNOPSIS...
Isolated mountain thunderstorms continue through midweek (15-30%
probability) as our low to the southwest moves slowly north-
northwest. Increasing temperatures through midweek before cooling
into the weekend. A Heat Advisory for the Valley and portions of
the lower foothills (mainly for elevations below 2000 feet) will
be in effect from 11 AM today through 11 AM Thursday.

&&

.DISCUSSION...
High clouds continue to stream in from the east across the
southern Sierra, into the southern Sacramento and San Joaquin
Valleys before exiting to the West Coast. Temperatures continue
to trend warmer than previous nights because of this as clouds
moderate the typical cooling pattern. The overall threat of
thunderstorms from last evening has ended until conditions renew
this afternoon over the Sierra.

Our pattern of an upper-level ridge in the northwest and an upper-
level low to our southwest continues and will support isolated
chances of showers and thunderstorms across the Sierra. Today's
orientation will be a more southeasterly flow pattern from the
mountains and develop further north as the low to the southwest
circulates energy through our forecast area. There is a slight
chance of seeing showers outside the mountains but the current
setup of the atmosphere will keep the majority of it as virga with
quickly thinning clouds. Moisture continues to be mainly
restricted to the mid-levels of the atmosphere, which discourages
any additional storms from developing once away from elevation.
Locally breezy conditions at times with gusts around 20-25 kts
near Redding this evening. Additionally, the circulation will add
to cloud cover the Sacramento Valley similar to this morning's
stream of clouds.

Moderate widespread HeatRisk and localized major HeatRisk across
the valley expected today as the ridge to our north strengthens
and warm our CWA to near triple digits today, with the northern
Sacramento Valley seeing low 100s. Given areas of moderate
HeatRisk and patches of local major HeatRisk, the Heat Advisory
for the Valley and portions of the lower foothills (mainly for
elevations below 2000 feet) continues to track and will be in
effect today at 11am through 11pm Thursday.

//Anderson

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.EXTENDED DISCUSSION (Friday THROUGH Monday)...
Much cooler weather is expected to return late this week into
early next week as ensembles continue to point toward stronger
troughing developing across the region. High temperatures are
forecast to lower to around 5-10 degrees below average over the
weekend. The mountains will continue to see a chance for mainly
diurnal showers and thunderstorms. Locally breezy winds are
expected at times.

&&

.AVIATION...
VFR conditions will predominate the next 24 hours. Scattered late
day thunderstorms are forecast to develop over the mountains
(mainly 21Z-04Z), and a few high-based showers may drift over the
Sacramento Valley tonight. Areas of southerly surface wind gusts
15-25 kts northern Sacramento Valley 22Z-03Z, mainly under 12 kts
elsewhere.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 11 PM PDT Thursday for
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.

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