Olympic Valley, California 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

190
FXUS65 KREV 201201
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
401 AM PST Sat Dec 20 2025

.KEY MESSAGES...

* Gusty winds are forecast today along with more shower chances
  which increase going into the night.

* While strong winds return tomorrow, heavier rains are likely
  early Sunday through Monday that could lead to localized
  flooding concerns.

* Another storm or two could bring significant rain and snow Tuesday
  into Christmas Day, but confidence in the details remains mixed.

&&

.DISCUSSION...

Today: Forecast guidance shows a generally westerly flow aloft
through most of the day with the occasional shortwave disturbance
over CA. This pattern changes going into the night as a PacNW trough
is seen developing that will give the upper air flow a southwesterly
component. As a result, gusty winds can be expected today with the
Sierra ridges seeing a 40-60% NBM probability of max wind gusts of
50+ mph out of the west-southwest. As for precipitation chances for
today, the models give the Sierra a 40-60% chance for a light shower
through the afternoon with Sierra Front areas having a 20-40%
chance. P-type looks to be mostly rain as forecast snow levels
will be around 8-8.5 kft around the Tahoe Region with the Eastern
Sierra having coming in with 9-9.5 kft early today. But precipitation
chances expect to increase this evening and going through the
night with coverage spreading more into western NV as well. Rain
intensity does look to pick up as well with rainfall rates looking
to begin to surpass 0.1 inches per hour at the crest by around
6-7 PM and continue to increase going into the night. With
overnight snow levels looking to be 9-10 kft, only the highest
peaks may see a few inches of measurable snowfall. Roads may be
slick and visibility could decrease as rainfall intensifies, so
please use caution if traveling tonight.

Sunday and Monday: With the Pacific trough continuing to develop,
this pattern aloft allows precipitation chances to continue. When
looking at the CW3E`s GEFS AR landfall tool, the pattern also favors
atmospheric river moisture pumping into the CWA especially in
northeastern CA and the Tahoe region. The latest blended guidance
continues to show a 48-hr QPF total through Monday afternoon
between 4.5-5.5 inches from Tahoe northward along the Sierra.
Lower Sierra valleys and northeastern CA still have a 70-80%
chance of at least 2.5 inches of rainfall during this time. As
such, the Flood Watch continues for the Tahoe Basin northward up
through Lassen County for Sunday through Monday. More details on
potential impacts are available in the hydrology section.
Elsewhere, there looks to be a 50-60% chance of at least 1.5
inches along the Sierra Front and the Eastern Sierra. Spillover
may be limited during this time except for northern Washoe County
where they could see as much as around 1-1.2 inches of QPF. As QPF
amounts taper off going eastward, the rest of western NV looks to
see generally under 1 inch of QPF possible during this period.
Snow levels are forecast to be 8.5-9.5 kft at the Tahoe region
going south through Mono County on Sunday and then drop to around
7.5-8.5 kft by Monday afternoon. Northeastern CA may see slightly
lower snow levels of 7.5-8 kft on Sunday that drop to around 7-7.5
kft by Monday morning. Another concern appears to be some
enhanced winds causing aviation and marine impacts on Sunday into
early Monday with a cold front passage. While Lake Wind
Advisories have been issued for Lake Tahoe and Pyramid Lake, we
will be monitoring model guidance in case winds trend upward
towards Wind Advisory criteria. Sierra ridge winds on Sunday could
be similar to those experienced today if not a tad faster with
the RRFS showing 700 mb winds around 70 knots.

Tuesday and beyond: Models are showing precipitation chances
persisting as the strengthening Pacific trough allows for some
cooler storms to move through the area going through the Christmas
holiday. Snow levels look to drop far enough where there may be
daily travel impacts over the Sierra passes. Not enough confidence
just yet to issue winter weather products particularly in the
Sierra, but please keep an eye on the forecast especially if you
plan to travel for the holiday. The Reno-Tahoe International
Airport currently has 25% NBM probability of seeing at least 0.1
inches of snow on Christmas Day which repeats on December 26th.
Will continue to monitor this going forward, but please be
prepared for travel delays and other impacts this week. -078

&&

.AVIATION...

The forecast calls for LLWS at all area TAF sites today going into
tomorrow. KRNO/KCXP/KMEV see VFR conditions throughout the day
with mostly dry conditions ahead of rain chances beginning in the
late afternoon/evening that continue into tomorrow. Sierra rain
chances persist this morning before tapering off a bit in the
afternoon. KTRK/KTVL have MVFR ceilings in the forecast this
morning ahead of sub-VFR visibilities this evening when rain
chances increase going into the night. VCSH for KMMH expects to
continue into the afternoon with precipitation chances returning
overnight after a brief break in the evening. Enhanced winds
return to the forecast on Sunday ahead of an approaching cold
front with precipitation chances continuing through at least
Monday. -078

&&

.HYDROLOGY...

Moderate to heavy rains will lead to significant rises on rivers and
streams Sunday 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 and the West Fork of the Carson near Woodfords
are currently expected to exceed action stage and minor flooding can
not be ruled out in these area. 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
fast rises and renewed flooding concerns. In other areas,
lowering snow levels will reduce flooding concerns into next week.

Enhanced runoff and sediment transport are likely below recent burn
areas, but debris flows are not expected. Watch for additional rises
near Christmas Eve and possible flooding concerns especially in
drainages with large mountain drainages below about 6,000 feet, like
the Susan River for example.

You can find river forecasts updated twice daily at:
www.cnrfc.noaa.gov

-Tim

&&

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

     Lake Wind Advisory from 10 PM this evening to 4 AM PST Monday
     NVZ002.

     Lake Wind Advisory from 4 AM Sunday to 4 AM PST Monday NVZ004.

CA...Flood Watch from late tonight through Monday afternoon CAZ071-
     072.

     Lake Wind Advisory from 10 PM this evening to 4 AM PST Monday
     CAZ072.

&&

$$