064
FXUS66 KSTO 172021
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
121 PM PDT Tue Sep 17 2024

.Synopsis...
Dry today then cooler unsettled weather tonight through
Wednesday. Lingering showers over the Sierra Nevada Thursday,
otherwise drier and warmer conditions into early next week.

&&

.Discussion...
A quiet weather day expected with dry and cool conditions over
Northern CA. Highs today and Wednesday will be in the mid 70s to
low 80s in the Valley with upper 60s to mid 70s over the
foothills as cooler weather continues ahead of our next weather
system.

Our next weather system moves in from the Pacific NW
tonight through Thursday AM. Compared to Sunday`s system, this
system is tracking further south and is warmer. This translates to
as a weaker thunderstorm signal for our area and lesser chances
for snow along the peak of the Sierra. Current probability is
15-30% of thunderstorm development over the Sierra and adjacent
foothills with highest chances along the ridge of the Sierra
Wednesday afternoon and evening (Wed 21z - Thu 03z. Forecast show
around 0.10-0.50 over the Sierra and foothills, up to just under
an inch along the Sierra crest. Probabilities of exceeding 0.25"
for the aforementioned area is 55-80% over the Sierra with 40-60%
over the foothills. The lower portions of the Valley (below 1000
feet) have 10-30% chance, which is more so indicating the slight
chance of showers moving through the Valley than any organized
stratiform precipitation.

This weather pattern will bring another chance of debris flow
issues over the Park Fire burn scar, albeit less synoptic support
compared to last weekend. One hi-res model simulations shows
isolated thunderstorms tracking over the burn scar early Wednesday
afternoon from east to west until Wednesday evening around 8pm
local.

After Thursday morning, heights are expected to rise behind the
weather system, returning temperatures to near normal by weekend`s
end. Thursday and Friday will see afternoon highs warm to the mid
90s to low 90s in the Valley with upper 60s to mid 80s across the
mountains to foothills areas. With the warming temperatures,
afternoon humidities lower back to 20-30% over the Northern
Sacramento Valley.

&&


.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...

Dry weather expected through the extended forecast period as high
pressure extends inland over NorCal. Warming trend forecast over
the weekend into early next week with 90s returning in the Central
Valley and 60s to 80s for the mountains and foothills.

&&

.AVIATION...


Mainly VFR conditions and surface winds below 12 knots over
interior Northern California. Isolated MVFR/IFR conditions may
happen due to rain showers. Southwestrly winds up to 20 knots are
possible in the Delta region.

&&

.STO WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$