906
FXUS66 KSTO 250924
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
224 AM PDT Tue Mar 25 2025

.SYNOPSIS...
Dry and mild weather continues today before a transition toward
cooler and periodically more active weather from Wednesday onward.
Confidence then continues to increase in a trend toward
widespread wetter weather moving into early April.

&&

.DISCUSSION...
Clear skies persist once again this morning as ridging aloft
remains in place. This stagnant pattern is keeping light winds for
most locations as well outside of locally breezy terrain driven
winds. As a result, another mild start to the day is expected with
low temperatures in the 50s through the Delta, Valley, and
foothills as 40s to low 50s persist at higher elevations. After
the warm start, seasonably warm high temperatures look to prevail
this afternoon, with some locations nearing record high
temperatures again. Current probabilities of high temperatures
reaching 85F sit around 40 to 70% through the Delta and Valley
locations from Interstate 80 southward, with 60 to 95 percent
probabilities further northward.

While troughing will begin to impact the region by midday
Wednesday, another mild overnight period will keep high
temperatures into Wednesday comparably cooler, but still above
normal for late March. Initial impacts from, the approaching
trough will be tied to increasing southerly winds through the
afternoon. Gusts 25 to 35 mph are expected for much of interior
NorCal, although some 60 to 90 percent probabilities of gusts to
40 mph do exist, primarily favoring the northern Sacramento Valley
and the Sierra/southern Cascades crest.

The introduction of this long wave trough will induce broad west-
northwesterly into interior NorCal from Wednesday into the
weekend. This will keep the weather pattern active as periodic
shortwaves progress through the region. The collocation of
moisture advection and seasonably warm temperatures ahead of the
first shortwave will likely yield anomalous instability across the
region by Wednesday afternoon. Despite this, thunderstorm
activity is expected to remain conditionally dependent upon
proximal forcing and cooling aloft as the trough nears the NorCal
coast. As a result, highest probabilities for thunderstorm
development, around 20 to 30 percent, are expected throughout the
northern Sacramento Valley and surrounding terrain, with some
lower 5 to 15 percent probabilities along the Sierra.

As periodic shortwaves impact the region through the remainder of
the week, some light mountain snow is anticipated as well. Snow
levels through Friday are generally expected to remain around 4000
to 5000 feet at this time, with most accumulating snowfall above
5000 feet. While accumulations from either of these individual
systems are expected to be light, current probabilities of
exceeding 4 inches of snowfall through Friday evening do sit
around 30 to 60 percent from Highway 50 northward at this time.

&&

.EXTENDED DISCUSSION (Saturday THROUGH Tuesday)...
Ensemble guidance indicates some potential for a brief lull in
precipitation impacts over the weekend before active weather
returns late weekend into next week. Some uncertainty persists,
particularly regarding timing and magnitude of heaviest
precipitation, but these additional systems moving into early
April are expected to draw from atmospheric river moisture. As a
result, a trend toward more widespread precipitation chances is
anticipated through the latter portions of the extended forecast
period. While exact details remain largely uncertain, periods of
at least moderate precipitation and gusty winds will be possible
into next week, with increasing confidence in at least some
attendant travel impacts. Otherwise, temperatures through the
weekend and into early next week are expected to remain generally
below normal as April begins on a cool note.

&&

.AVIATION...
Mainly VFR conditions across interior NorCal the next 24 hours.
Around a 10-20% chance off 1/2SM or less due to BR/FG from 10z to
17z in the central/southern Sac Valley and northern San Joaquin
Valley this morning. Surface winds below 12 knots and variable.

&&

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

$$