047
FXUS66 KSTO 052129
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
229 PM PDT Sat Oct 5 2024

.Synopsis...
Well above normal temperatures persist through the weekend, with
Moderate to Major HeatRisk in the Valley, Delta and foothills.
Slight chance of high elevation mountain showers Sunday and Monday
afternoon over the Sierra Crest. Gradual cooling trend next week
with shower chances mainly north of I-80 and over higher terrain.

.Discussion...
Current GOES-West visible satellite imagery shows clear skies with
abundant sunshine being observed across interior Northern
California on this Saturday afternoon. Current temperature
observations are trending approximately 2-5 degrees higher than
this time 24 hours ago, in the 90s in the Valley, Delta, and
lower foothills, and 70s-low 90s in the upper foothills and
mountains, valid at 230 PM PDT.

Upper level ridging is allowing for unseasonably hot temperatures
and dry conditions to prevail through the weekend. Widespread
Moderate to Major HeatRisk is expected through Sunday in the
Valley, Delta and foothills. Forecast highs remain in the 90s to
low 100s, with warm overnight lows in the 60s to mid 70s. The
Heat Advisory remains in effect through 11 PM PDT Sunday evening
for those aforementioned locations. Temperatures cool slightly on
Monday but are still unseasonably hot, with Moderate HeatRisk
across the Valley and foothills. A few isolated mountain showers
will be possible over the Sierra Crest on Sunday and Monday
afternoons as a subtle trough approaches the region.

By Tuesday, temperatures look to be on a gradual downward trend
with highs in the 90s in the Valley, 80s in the foothills and 70s
to 80s in the mountains. HeatRisk lowers to the Minor category
with just some localized Moderate HeatRisk. Low daytime relative
humidity continues, in the teens and 20s through Tuesday, with
moderate to poor overnight recoveries.

&&

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
Ensemble guidance and cluster analysis indicate upper level
troughing developing over the Eastern Pacific and approaching from
the west mid to late next week, bringing a cooling trend through
the end of the week with increased onshore flow. HeatRisk is
expected to decrease and remain in the Minor category over the
extended forecast period. The troughiness will also bring a chance
for showers toward the end of the week. There is still some
uncertainty in exact timing and details, however the National
Blend of Models (NBM) currently advertises a 10-25% probability of
a tenth of an inch of precipitation or greater on Friday, mainly
north of Interstate 80 and over higher terrain. On Saturday, upper
level ridging looks to build back in behind the trough resulting
in slightly warmer temperatures and increased northerly flow.

&&

.AVIATION...
VFR conditions are expected over interior northern California for
the next 24 hours. Surface winds are generally expected to be
below 12 knots except for locally northeast or northwest surface
wind up to 15 knots with gusts up to 20 knots in the Delta,
foothills and mountains after 10Z Sunday.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 11 PM PDT Sunday for Carquinez Strait and
Delta-Motherlode-Northern San Joaquin Valley-Southern Sacramento
Valley.

&&

$$