Sierra-at-Tahoe

000
FXUS66 KSTO 311910
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
1210 PM PDT Sat Oct 31 2026

For additional details on weather and expected impacts over the
next 7 days, please visit weather.gov/sto/briefing.


.KEY MESSAGES... 
 
 - Winter Weather Advisory in effect through 7 AM Sunday for the 
   Sierra elevations above 7000'

 - Rain and mountain snow showers continue today into Sunday for 
   the Sierra and surrounding areas, accompanied by isolated 
   thunderstorm chances this afternoon and evening

 - Quick moving system brings shower/isolated thunderstorm chances
   Tuesday-Wednesday

 - Below normal temperatures continue through the weekend and into
   the week ahead alongside periods of breezy winds
 
&&

.DISCUSSION...

This Weekend:
A positively tilted trough system sweeps across California today 
into Sunday, quickly ejecting out of the region late in the day on
Sunday. The associated northern trough of this system will bring 
the primary impacts to the region. While the bulk of any 
atmospheric river moisture looks to stay well south of interior 
NorCal with this system, ample moisture remains in place for 
continued rain/snow showers and isolated thunderstorm chances 
across the Sierra and adjacent foothills northward toward the 
southern Cascades and Burney Basin. Earlier this morning, embedded
thunderstorms were observed across Tuolumne/Calaveras/Amador 
counties with indications of lingering instability across a 
similar area still nearing the middle of today. 

As a result, moderate rainfall will be possible with any showers 
that develop throughout the day. While thunderstorm activity 
generally looks to remain more embedded owing to persistent cloud 
cover, an area of clearing across the northern San Joaquin Valley 
toward the lower foothills will likely result in a few stronger 
thunderstorms capable of brief heavy rain, gusty winds, near 
severe hail, frequent lightning, and some low potential for a 
brief funnel cloud or weak tornado. Highest chances for 
thunderstorms (up to 25%) remain confined to the Sierra/foothills 
along and south of Interstate through this evening. 

As for winter impacts, a Winter Weather Advisory remains in 
effect through 7 am Sunday along the Sierra for elevations above 
7000'. At this time, accumulating snowfall has remained above 
7000' with snow levels around 7000'-8000' through today lowering 
toward 5500'-6500' into Sunday as precipitation begins to taper 
off. Forecast snowfall totals remain largely unchanged with 
accumulations up to 10" expected above 7000', up to 18" at peaks, 
up to 3" possible between 6000'-7000', and flurries to a dusting 
as low as 5500'. Minor travel delays from chain controls and slick
travel conditions will be possible for mountain passes within the
Winter Weather Advisory, so be sure to check quickmap.dot.ca.gov 
for latest road conditions this weekend.

Heaviest precipitation remains anticipated through Sunday 
morning, with lingering mountain showers tapering off throughout 
the day on Sunday as the system quickly exits the region. While 
increasing north to east winds are expected Sunday afternoon into 
Monday morning, the rapid ejection of the trough will keep the 
duration of favorably aligned winds aloft minimal. As a result, 
north winds gusting 15-20 mph are anticipated throughout the 
Valley Sunday afternoon, alongside downslope east winds gusting 
25-35 mph along the Sierra overnight into Monday morning. 

The Week Ahead:
As quickly as the trough moves eastward and ridging builds in 
behind it into Monday, another shortwave trough will be gearing up
to quickly pass through interior NorCal Tuesday into Wednesday. 
This will yield a briefly drier period Monday into early Tuesday 
ahead of the system. Ensemble guidance then remains in relatively 
steady agreement on increasing chances for showers and isolated 
thunderstorms by midday Tuesday, with mountain shower chances into
early Wednesday, followed by an additional period of increasing 
north to east winds as the system departs. Rainfall totals look 
notably lighter at this time with generally a 10-25% chance of 
precipitation greater 0.25" Tuesday-Wednesday. Snow levels also 
look to remain around 6500'-7500'+, with minimal snowfall impacts 
anticipated. 

Forecast certainty continues to diverge after this period into 
the end of the week. A likely drier period does look to follow the
midweek ejecting trough, but exact duration of dry weather 
remains dependent upon any subtle shortwave systems moving through
remnant west-northwest flow aloft through the end of the week as 
well as the exact logistics of longwave troughing building in 
over the Gulf of Alaska. For now, generally dry weather, near to 
slightly above normal temperatures, and periodically breezy 
offshore winds are favored late week into next weekend. 

&&

.AVIATION...
VFR conditions are generally expected to prevail at 
TAF sites across the next 24 hours, although showers/isolated 
thunderstorms may briefly introduce MVFR/IFR conditions through 
05z Sunday. Otherwise light winds less than 12 kts persist at TAF 
sites as well. Across the Sierra, MVFR/IFR conditions will be 
likely and LIFR possible as scattered rain/snow showers and 
isolated thunderstorms persist through 12z Sunday, tapering off to
lingering light showers the remainder of Sunday morning. 

&&

.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 7 AM PDT Sunday for Sierra (Cal-
Tuo) Above 5000 ft-Sierra (El Dorado-Amador) Above 5000 ft-
Sierra (Sierra-Placer) Above 5000 ft.

&&

$$