796
FXUS66 KSTO 232119
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
119 PM PST Sat Nov 23 2024

.SYNOPSIS...
Periods of rain and mountain snow expected through Tuesday with
breezy southerly winds. 10-20% chance of isolated thunderstorms
this afternoon and evening. Dry conditions expected on Thanksgiving
continuing into the weekend.

*Winter Storm Warning: Until 4 PM Tuesday for elevations above
 6000 feet along the Sierra/ Southern Cascades including
 Interstate 80 and Highway 50.

.DISCUSSION...
A much quieter weather picture late this morning with just a line
of showers through the Southern Sacramento Valley to the Sierra
with continued mountain snow and localized flooding impacts. The
brunt of the rain fell over the last 36 hours with 2-4" reported
over the Sierra and Northern Sac. Valley, up to 6 inches near the
higher terrain by Quincy. The Valley floor saw anywhere from half
an inch to up to 3 inches across Sacramento Metro. The Sierra
foothills saw 2-4 inches up to 6 north of HWY. 50. Flood impacts
continue to linger so please check quickmap.dot.ca.gov for the
latest updates on road closures and possible travel delays.

We will see impacts transition to snow today into early next week
as the weather system continues over Interior Northern CA. We can
expect scattered showers with isolated chances for thunderstorms
through this evening with the best chances from the Northern Sac.
Valley near Redding through the Sierra foothills north of Hwy.50.
With any thunderstorm brings the threat of brief heavy rain
showers, lightning, breezy winds, and small hail.

Today`s rain totals will be variable and dependent on shower and
thunderstorm development but can expect roughly 0.01-0.50" with
higher amounts as you move east and up in elevation. After today,
rain will be showery in nature with periods of light to moderate
rain and not the continued periods of heavy rain we experienced
over the last 24-48 hrs. Rain totals for the Valley Sunday through
Tuesday afternoon are roughly 0.50-1.50", highest across the
foothills and as you approach the Northern Sacramento Valley. THe
next heaviest period of rain is forecasted to be Sunday late
morning into Monday morning.

Periods of heavy snow continue through early next week for the
Sierra and Southern Cascades. An additional 4 to 8 inches is
expected today, heaviest just north of I-80, as showers make their
way across the mountain. For Sunday - Tuesday, forecasts show an
additional 8 to 18 inches, up to 2 to 3 feet along mountain peaks.
Heaviest amounts are forecasted to be south of Hwy. 50 and near
Lassen National park with the Winter Storm Severity Index showing
best chances (40-70% chance) for moderate impacts south of Hwy.
50. NBM probability shows 45-80% chance of 12 inches of more from
this evening to Tuesday afternoon. Snow levels decrease this
evening before settling at around 4000-5000 feet, up to 5500 feet
into Monday morning before increasing to 5000 to 6500 feet by
Monday evening into Tuesday. As a result, our Winter Storm Warning
remains in effect above 5500 feet for storm accumulations of 1 to
3 feet up to 4 feet across portions of the Sierra and Southern
Cascades. Snow- covered roads, chain controls and travel delays
are likely which will result in very difficult travel at times
above 5500 feet.

Temperature trends will be relatively unchanged in the short term
with Valley highs in the 50s with mid 30s to low 50s across the
mountains and foothills.

.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...

Ensemble guidance and cluster analysis are in good agreement in
depicting upper-level ridging returning over Northern California
mid to late week. Dry conditions expected through Thanksgiving
with slightly below normal temperatures and light to breezy north
winds into the weekend. NBM attempts to bring in slight chances of
rain (10-25%) to areas south of Interstate 80 with very light rain
to sprinkles possible over the mountains Thursday night into
Friday morning.

&&

.AVIATION...

Scattered light to moderate precipitation will result in periods
of VFR/MVFR conditions across the Valley with local areas of
IFR/LIFR in the foothills and mountains till 07Z Sunday and after
16Z Sunday from heavier showers developing. There is a 10-20%
chance of thunderstorms in the Valley/foothills through this
evening. Periods of gusty southerly winds 15 to 20 knots in the
Valley and foothills until 01Z Sunday. Southeasterly gusts 30 to
40 knots over the Sierra to continue until 12Z Sunday. There is a
chance of MVFR/IFR conditions from patchy fog in the Southern
Sacramento Valley early tomorrow morning.


&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 4 PM PST Tuesday for West Slope
Northern Sierra Nevada-Western Plumas County/Lassen Park.

&&

$$