000
FXUS66 KSTO 250955
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
255 AM PDT Thu Apr 25 2024

.Synopsis...
Light rain and mountain snow this afternoon through Friday with
thunderstorm chances today and tomorrow, and best chances over
the foothills and mountains.

&&

.Discussion...
Another quiet night across Northern California outside of some
scattered cloud cover and breezy Delta winds. As of midnight,
observations show gusts 15 to 25 MPH in the Delta area, slowly
trickling down as the morning continues and returning in the
afternoon. Ensembles show a trough dropping down from the
northwest, moving into the Great Basin, that will bring
precipitation across our forecast area today into Friday, highest
over the mountains. Light sprinkles are possible across the
Sierra and Southern Cascades with a heavier precipitation
expected Thursday afternoon through Friday morning. Latest WPC QPF
totals are 0.25-1.00" over the mountains, 0.10-0.50" over the
foothills and 0.01-0.15" in the Valley, albeit dry over the Delta
and portions of the Northern San Joaquin Valley. Thunderstorms
will be possible this afternoon and evening (10-20% chance),
primarily north of I-80 through the northeast foothills. Friday
shows a better chance of thunderstorm development (15-30% chance),
highest over the I-80 and Hwy.50 corridor over the Sierra.
Lightning, brief heavy rain, gusty winds, and small hail will be
possible with any thunderstorms that develop.

Today`s weak system will bring snowfall to the Sierra, but no
moderate travel impacts are expected. Snow levels will be 7000 to
8000 feet initially, lowering to 5500 to 6500 feet by Friday late
morning. Totals will only amount to a few inches, up to 8-10
inches along mountain peaks above 7000 feet. NBM probabilities
point to a lower snow totals with probabilities of 4 inches or
more only being 10-25% south of Hwy. 50 and less than 10%
elsewhere. Heaviest snowfall will be late Friday morning before
tapering off throughout the afternoon.

By Saturday, weak ridging develops over NorCal that will quiet any
lingering precipitation and warm afternoon Valley highs to the
mid to upper 70s and upper 40s to 60s across the mountains and
foothills respectively.

&&

.EXTENDED DISCUSSION (Monday THROUGH Thursday)...

Progs suggesting enough ridging in place over interior NorCal
Monday and Tuesday to keep short wave troughs north of the CWA.
Cluster analysis showing broader divergence in solutions beyond
Tuesday leading to increased forecast uncertainty midweek. EC now
maintaining more ridging in place resulting in continued dry
conditions, while GFS supports deeper troughing with potential for
mountain precip Wednesday night into Thursday. NBM leans toward
the GFS with POPs and forecasts above normal high temperatures
Monday into Wednesday, then below normal Thursday.

&&

.AVIATION...
Pac storm will bring a threat of showers, higher elevation mtn
snow showers and slight chance of thunderstorms next 24 hrs.
Mainly VFR conditions thru 12z Fri except areas MVFR/IFR
conditions possible over the mtns in precip. Snow levels above
7000 ft lowering to 5000-6000 ft Fri AM. In Central Vly, sfc wind
mainly below 12 kts til 21z Thu, then areas Sly sfc wind 15-20
kts. Vcnty Delta, SWly sfc wind 15-25 kts. Over mtns, areas Wly
sfc wind gusts up to 30 kts possible aft 18z Thu.

&&

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

$$