Sierraville, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

468
FXUS65 KREV 212040
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
1240 PM PST Sun Dec 21 2025

.KEY MESSAGES...

* Heavy rains that could lead to localized flooding, along with
  strong to damaging winds, and heavy wet snow in the Sierra above
  8000 feet continue into tomorrow.

* Following the beginning week system, a brief lull in
  precipitation is seen during the day on Tuesday with gusty
  ridge winds.

* Another round of stormy conditions could bring significant rain
  and snow along with enhanced winds late Tuesday through
  Christmas Day.

&&

.DISCUSSION...

Significant moisture continues to stream across northern California,
along with gusty winds. Areas of heavy precipitation have been noted
from I-80 and points northward, which prompted us to issue a
Flood Watch for northeastern California and the Tahoe area (see
product details below). In their latest Excessive Rainfall
Outlook, the WPC has recently highlighted a slight risk (at least
a 15% chance of excessive rainfall) within the CWA for areas
generally along and west of a line from Bieber-Susanville-Truckee-
South Lake Tahoe in CA. With snow levels hovering above 9000 feet
this morning, the majority of the precipitation is falling as
liquid water. The absence of snowpack below this level is slowing
the flood response on some creeks and streams, with warmer soils
allowing the response to be gradual thus far. We will continue to
monitor the area creeks and streams today, especially the Susan
River at Susanville, which tends to be a flashy stream and can
rise quickly under the right conditions.

Another consideration today is the High Wind Warning and Wind
Advisory through 4AM Monday. Gusts have already been clocked as high
as 90+ mph around the Tahoe Basin today. Gusts across the Sierra
Front have ranged 40-60 mph, with wind prone areas seeing the higher
gusts. If you haven`t already secured your holiday decorations,
Frosty may already be an unidentified flying object this afternoon.

As this system continues to bring wind and rain, the focus of the
greater amounts of precipitation will be for the western Lassen
County to Tahoe area through late Monday. Precipitation will begin
to taper into Tuesday morning, with Tuesday offering a brief break
in the action. By the time this portion of weather moves along to
the east, we could see QPF of up to 2-6" of liquid water along and
north of I-80. With some gauges already measuring in that range,
this is proving to be a windy, wet system.

As mentioned briefly above, Tuesday will offer the best window for a
break in the weather. While there will still be showers along the
western slopes of the Sierra, our side will have to wait our turn.
Late Tuesday, as the atmospheric river oscillates north to south
along the Sierra, the spillover will hold off until it settles over
Mono County and begins to push over the mountain range.

This next round of stormy weather could start rather different than
it begins. Snow levels overnight Tuesday into Wednesday will start
out above 7500 feet, abruptly tumbling as Tuesday turns to
Wednesday. By midday Wednesday, snow levels will be tumbling to
below 6000 feet to near 5500 feet by Thursday morning. So if you are
wondering whether you will have a White Christmas (1" on the
ground by 7 AM Christmas morning), you will have a better
opportunity above 6000 feet. However, if you wait until late
Thursday night, you are more likely to see measurable snow. The
Tahoe Basin has a 20-30% chance for gathering 6" of fresh snow by
Christmas morning, while our friends in Mono County have a 70-80%
chance of 6" by 7AM Thursday. The foothills including Virginia
City have a 10-20% chance for 6" of new snow by Thursday morning.
But that will not be the end of the snowfall, as the bulk of the
snow will arrive for the day Thursday. Travel across the Sierra
will be difficult to impossible at times, with lower elevations
getting in on the action late Thursday as snow levels continue to
fall.

By Friday, snow levels will have found the valley floors, with
widespread residual snow showers tapering into the weekend. HRICH

&&

.AVIATION...

An impactful atmospheric river system is bringing rainfall
today into tonight that could be moderate to heavy at times, from
Alpine County north through Lassen County including in the
Greater Lake Tahoe area. As the intensity of this precipitation
increases this afternoon, KTRK/KTVL will see visibilities decrease
to IFR/LIFR levels later today. NV TAF sites may occasionally
drop to MVFR visibility when rain occurs. Higher elevations in the
Sierra may see snow today while KTVL could see a rain/snow mix
tonight. Terrain obscuration in areas of heavy precipitation is
expected. Area- wide LLWS, surface winds up to around 40-50 kts,
and ridgetop winds gusting up to 100 mph are also to be expected
this afternoon. Impacts of this wintry system will continue into
tomorrow before tapering off overnight Monday going into Tuesday.

-078/HRICH

&&

.HYDROLOGY...

Ongoing moderate to heavy rains are resulting in significant rises
on rivers and streams today into Monday most notably from Alpine
County north through Lassen County.

Minor flooding of small streams, urban and poor drainage areas and
rockfall in steep terrain are possible during any prolonged periods
of high intensity rainfall.

While no mainstem river flooding is currently forecast, the Susan
River near Susanville is currently expected to exceed action stage
and minor flooding can not be ruled out. Remain aware of the
potential for additional river and stream rises near Christmas Eve
in large mountain drainages below about 6000 feet, like the Susan
River. In these areas additional rain and saturated conditions could
lead to rapid rises and renewed flooding concerns. In most other
areas, lowering snow levels will reduce flooding concerns into next
week.

Enhanced runoff and sediment transport including rock fall are
likely within and below recent burn areas, including, but not
limited to the Davis and Bear burn areas. Post-Fire debris flows are
not expected.

You can find river forecasts updated Sunday at ~3PM and ~9PM,
then ~ 9am and ~3PM Monday and Tuesday at: www.cnrfc.noaa.gov

-Tim

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch through Monday afternoon NVZ002.

     Wind Advisory until 4 AM PST Monday NVZ001-002.

     Winter Storm Watch from Tuesday evening through Friday morning
     NVZ002.

     Winter Weather Advisory from 4 PM this afternoon to 1 PM PST
     Monday NVZ002.

     High Wind Warning until 4 AM PST Monday NVZ003.

     Lake Wind Advisory until 4 AM PST Monday NVZ004.

CA...Flood Watch through Monday afternoon CAZ071-072.

     Wind Advisory until 4 AM PST Monday CAZ071-072.

     Winter Storm Watch from Tuesday evening through Friday morning
     CAZ071>073.

     Winter Weather Advisory from 4 PM this afternoon to 1 PM PST
     Monday CAZ072-073.

     High Wind Warning until 4 AM PST Monday CAZ073.

&&

$$