000
FXUS66 KSTO 281049
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
339 AM PDT Sat Mar 28 2020

.Synopsis...
Unsettled weather is expected over the weekend with showers and
mountain snow showers. Threat of showers persists in the north
Monday and Tuesday, otherwise drier and much warmer into the
middle of next week.

&&

.Discussion...
Warm advection is spreading light precipitation into the
northwestern California coast ahead of a positively-tilted short
wave trough. Mesoscale models suggest this precipitation could
reach western Shasta County around 5-7 am, then spread into the
rest of the northern Coastal Range and Delta by 10 am, reaching
the northern Sierra by around noon. The trough tracks inland later
in the day. Model ensembles show rain amounts of around .05" to .15"
are expected by early evening. Snow levels are forecast to be around
4500-5000 feet, with snow amounts during the day ranging from a
dusting to an inch.

Conditions trend wetter Saturday night into Sunday as reinforcing
wave with a cold front pushes inland, but moisture is somewhat
lacking, so rain and snowfall amounts should remain light to
moderate. Have introduced a slight chance of thunderstorms Sunday
afternoon over the Delta and western San Joaquin Valley with some
modest instability there in potential clearing behind the front.

Total Valley rainfall amounts will range from 0.20 to 0.50 inches.
Over the Sierra/Cascade range, NBM projects 3 to 5 inches of snow
with higher amounts around mountain ridges. While snow rates and
total amounts are modest, some mountain travel delays are possible
on any snow covered roads.

On Monday, trough from the Gulf of Alaska passes through the
Pacific Northwest, with the southern portion of a cold front
brushing through the northern mountains and northern Sacramento
Valley. This will keep shower chances in those areas, with the
bulk of the precipitation remaining further to the north. Expect
cloudy skies along with periods of light rain showers to dominate
Monday with total amounts staying under a tenth of an inch. For
Monday, temperatures will rebound quite a bit from the weekend
with mostly sunny skies likely from I-80 southward.

Tuesday warms quite a bit, although some clouds and lingering
light showers remain possible over the mountains of Shasta County.
Valley highs in the low 70s are expected. This begins a warming
and drying trend. EK
&&
.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Ensemble mean and latest deterministic runs support the idea of
broad ridging amplifying by the end of next week resulting in dry
weather and gradually milder temperatures across the region.
Highs are forecast to around 5-15 degrees above average.

&&

.AVIATION...

Mostly VFR conditions are expected thru about 20Z, then areas of
MVFR with local IFR conditions as showers develop across the
region. Snow level 040-050. Winds generally less than 10 kts.
&&

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

$$