Vallejo, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

152
FXUS66 KSTO 062118
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
218 PM PDT Sun Oct 6 2024

.Synopsis...
Anomalously hot temperatures will continue to be felt across
interior Northern California through Monday, resulting in
widespread Moderate to Major HeatRisk. Slight (5-15%) chance of
high elevation mountain virga showers or light sprinkles this
evening and then again Monday evening. Cooler temperatures slowly
creep in mid to late week, with near normal temperatures by the
weekend alongside another chance at mountain showers.

.Discussion...
Mostly clear and sunny skies prevail across Northern California
this afternoon, with GOES-West visible satellite imagery showing a
few high clouds over the southern Sacramento Valley and building
cumulus clouds along the Sierra crest. Anomalously hot weather
will continue through tomorrow as upper-level ridging remains in
place overhead. Highs will continue to be in the mid 90s to triple
digits with overnight lows in the mid 60s to upper 70s. These
unseasonable temperatures will result in an extra day of
widespread Moderate to Major HeatRisk and minimal overnight
relief, especially in the Delta and foothills. Accordingly so, the
Heat Advisory has been extended until 11 PM Monday. A weak
embedded trough will introduce a 5-15% chance of isolated showers
across the northern Sacramento Valley and vicinity mountains this
evening and then again Monday evening, mainly at higher
elevations. No measurable precipitation is expected.

By Tuesday, a developing trough along the California coast will
help promote breezy onshore flow during the afternoon and evening
hours, resulting in slightly cooler daytime and overnight
temperatures.

Wait, cooler temperatures??

Yes! Well, kind of.

The end to this oppressive heat is indeed in sight as the upper-
level ridge begins to breakdown. HeatRisk reduces to Minor on
Tuesday with areas of Moderate in the foothills on Tuesday, before
downgrading further to widespread Minor throughout the rest of
the week. Now while high temperatures will feel cooler, they will
still be about 5 to 15 degrees above October climatological
normals at least through Wednesday. Overnight lows will also see a
return to the mid 50s to low 60s. Relative humidities will slowly
increase in response to the onshore flow and introduction of a
more moist airmass. However, daytime values will still be in the
teens and low 20s Monday and Tuesday with poor overnight
recoveries in the foothills (Mon AM & Tues AM).

&&


.EXTENDED DISCUSSION (Thursday THROUGH Sunday)...
Ensemble guidance and cluster analysis indicate upper-level
troughing developing over the Eastern Pacific and approaching from
the west by mid to late week, bringing in cooler temperatures.
Minor HeatRisk will persist through the extended period, as
temperatures gradually decrease to near-normal by the weekend.
This upper-level trough will also bring a 15-30% chance for
showers in the northern Sacramento Valley, adjacent mountains and
foothills, mainly north of I-80 by late week and into the early
weekend. Due to the dynamic nature of this system, there is some
variability in storm track across the ensembles resulting in lower
forecast confidence of timing and details. NBM probabilities
suggest a 15-30% chance of 0.10" or more of precipitation, mainly
over the higher elevations of the Coast and Sierra Ranges with
minimal impacts. As the trough begins to breakdown over the
weekend, periods of northerly flow can be expected through the
Sacramento Valley alongside gusty downslope/easterly flow along
the Sierra.


&&

.AVIATION...
VFR conditions are expected over interior northern California for
the next 24 hours with surface winds are generally below 12 knots
except locally northwesterly and northeasterly up to 15 knots
with gusts up to 25 knots in the Delta, foothills, and mountains
after 05Z Monday.

&&

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

&&

$$