Grass Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

425
FXUS66 KSTO 231238
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
438 AM 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.

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


.DISCUSSION...
Light to moderate showers continue to move over the Sierra
foothills and mountains early this morning with lingering showers
in the northern San Joaquin Valley per RADAR.

Another band of scattered showers and mountain snow is expected
to push through the area later this morning through the early
afternoon. Behind this band, clearing in the Valley and foothills
will work to introduce instability resulting in a 10-20% chance of
isolated thunderstorms. Any storms that develop will be capable of
brief heavy rain, gusty winds, small hail, and lightning. If
thunder roars, GO INDOORS!

High-res models show a line of thunderstorms and moderate to brief heavy
rainfall moving west to east along the I-80 corridor this
afternoon and evening (roughly between 2-6PM). As this line moves
further into the mountains, rain will transition to snow
resulting in slick roads and hazardous driving conditions. The
main thunderstorm threat continues to remain south of the Park
Fire burn scar, but conditions will be closely monitored
throughout the day. Snow levels today will sit around 5000` in
elevation. From Saturday night into Sunday there will be a break
in precipitation as mainly dry with a few isolated areas of sprinkles
to light rain return to interior NorCal.

Scattered precipitation returns later in the day on Sunday,
bringing periods of rain to the Valley and foothills and moderate
to heavy mountain snow through Tuesday. Snow levels are set to
increase to around 5500` to 6000` on Monday. Additionally, some
clearing on Tuesday will lead to a 10 to 15% chance of isolated
afternoon and evening thunderstorms across the Valley and Sierra
foothills. Through Tuesday, forecast precipitation amounts are
between 0.75" to 1.75" in the Valley, 1.00" to 3.00" in the
foothills, and 2.00" to 4.00" in the mountains. The National Blend
of Models indicates a 20 to 40% chance of Valley accumulations
2.00" or greater, with 50 to 80% chance over the mountains and
foothills. Total snowfall accumulations are expected to be between
1 and 4 feet with up to 5 feet along the higher peaks of the
Sierra. As a result, the Winter Storm Warning is in effect until 4
PM.


.EXTENDED DISCUSSION (Wednesday THROUGH Saturday)...
A few lingering rain and mountain snow showers will be possible
on Wednesday as upper-level troughing flattens out. These will
gradually taper off throughout the day, with additional rainfall
accumulations less than an inch over the mountains and snowfall
amounts 3 to 5 inches above 6000`. 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 on Thanksgiving with slightly below normal
temperatures and light to breezy north winds into the weekend.

&&

.AVIATION...
Scattered light to moderate precipitation later today (13Z-02Z)
will result in periods of VFR/MVFR conditions across the Valley
and foothills with areas of IFR/LIFR in the mountains. There is a
10-20% thunderstorms in the Valley/foothills north of I-80 between
18z-03z. Periods of gusty southerly winds 15 to 20 kts in the
Valley until 00z Sunday, with gusts 30 to 40 kts over the Sierra.
Clearer conditions expected after 05Z Sunday.



&&

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

&&

$$