Heavy Snow in California, December 23 to 24, 2016

Area Forecast Discussion
National Weather Service Reno NV
243 AM PST Fri Dec 23 2016

.SYNOPSIS...
A winter storm will impact travel today through early
Saturday with heavy mountain snow and valley rain changing to snow.
Cold and dry conditions are anticipated for Christmas Day and
Monday. There will be a gradual warming trend through next week with
no storms expected.

&&

.SHORT TERM...
No major changes to the timing of the storm. Bulk of the system will
move through today and then exit the area on Saturday. Christmas Day
and Monday still look dry, but it will be brisk.

Northeastern CA/Tahoe Areas Timing
* 6AM-9AM Today: Light Snow
* 9AM-8PM Today: Heavy Snow
* 8PM Today-7AM Saturday: Snow Showers

Western Nevada Area Timing
* 10AM-3PM Today: Light rain/snow mix
* 3PM-10PM Today: Snow
* 10PM Today-10AM Saturday: Light Snow Showers

Mammoth Area Timing
* 9AM-10AM Today: Light Snow
* 10AM-10PM Today: Heavy Snow
* 10PM Today-7AM Saturday: Snow Showers

Bottom Line: Expect significant travel delays and winter driving
conditions for all Sierra Passes today and through early Saturday.
Be sure to check road conditions before you head out, as there could
already be chain restrictions in effect.

Winds will continue to pick up ahead of the storm this morning with
ridge wind gusts peaking around 100 MPH by later today. Wind gusts
along some of the ridges are already in the 60 to 70 MPH range early
this morning. Turbulence and LLWS are likely through the day today,
especially since the ridge winds will be quite strong, while the
valley wind speeds will remain in the 35 to 45 MPH for the most
part. There may be a brief period of wind gusts stronger than 45 MPH
as the cold front approaches this afternoon, but otherwise we are
not forecasting a prolonged period of strong wind gusts for this
storm.

Now onto the precipitation. Models are staying consistent with the
slightly faster storm track, as well as with the track being a bit
further south. The 00Z GFS/NAM continue to show heavier snowfall
south of Hwy 50. As far as snow levels, precipitation will start as
rain or a rain/snow mix below 5500 feet but quickly fall to valley
floors, especially where heavier spillover occurs. Best spillover
chances will be along and with the cold frontal passage between 3 to
6PM this afternoon. One thing to note is that the GFS continues to
show a moderate band of rain/snow across the Basin and Range where
snow levels may lower enough in time to produce an inch or two of
wet snow near and east of Hwy 95, including Fallon and Lovelock
Friday evening.

Confidence remains high for travel issues in the Sierra from Lassen
County south through Mono County. Confidence is a bit lower for
western Nevada snow amounts mainly due to uncertainty in location of
heavier spillover. This is a situation where Reno could see little
to none, whereas Minden, Carson Valley, and Gardnerville could see up
to 3 inches or more. Just depends on where the snow bands and
spillover focus. Our advice for travelers: stay updated on forecast
changes and check road conditions before you leave. Be prepared.

By Saturday, the bulk of the storm will have exited the region and
only residual light snow showers will persist off and on through the
day. On Sunday and Monday, it will be brisk, but predominately clear
with low impacts to travel due to weather on those days.  Valley
inversions are expected as winds remain light, with daytime highs
about 10 degrees below average for lower elevations. -Edan

.LONG TERM...
No changes were made to the extended forecast as a much quieter
weather pattern returns after Christmas.

For Tuesday-Wednesday, shortwave energy moving across the Pacific
Northwest will bring a bit more winds in upper elevations with
weaker valley inversions. This should allow temps to rise closer to
late December averages, around the lower-mid 40s. One exception will
be in areas north of Susanville-Gerlach, where a greater amount of
cloud cover and possible light snow showers will keep temps a few
degrees cooler.

By Thursday, ridge begins to rebuild over CA-NV for dry conditions
in all locations with light winds. Some inversions will likely
return, resulting in similar daytime temps between lower
elevations and Sierra valleys (highs mainly upper 30s-lower 40s).
MJD/Edan

&&

.AVIATION...
This storm will bring increasing winds today with a brief period of
valley gusts in the 30-40 kt range. Winds across ridges will reach
70-80 kts ahead of the cold front, leading to turbulence and
mountain wave activity. In addition, short periods of low level wind
shear are possible ahead of and along the frontal boundary today.

Precipitation will reach the Sierra and northeast California between
12-18z today, spreading into western Nevada between 18z today and
00z Saturday. Sierra terminals including KTRK, KTVL, and KMMH can
expect all snow with CIGS/VSBY at IFR/below landing minimums and
runway accumulations around 1 foot from the onset through late
tonight. For western Nevada terminals including KRNO and KCXP,
precipitation will likely start as rain, then turn to snow with
the cold frontal passage. 1 to 4 inches of snow accumulation are
possible through Saturday morning, with the higher end of this
range a little more favorable for KCXP-KMEV. Lesser snow amounts
(up to 1 inch) are expected for the valleys east of KRNO-KCXP to
the US-95 corridor. -MJD

&&

.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 4 AM PST Saturday NVZ005.

     Winter Storm Warning from 6 AM this morning to 7 AM PST Saturday
     NVZ002.

     Winter Weather Advisory from 4 PM this afternoon to 7 AM PST
     Saturday above 5000 feet in NVZ001.

     Winter Weather Advisory from 4 PM this afternoon to 7 AM PST
     Saturday NVZ003.

CA...Winter Storm Warning until 4 AM PST Saturday CAZ071.

     Winter Weather Advisory until 4 AM PST Saturday CAZ070.

     Winter Storm Warning from 10 AM this morning to 10 AM PST
     Saturday CAZ073.

     Winter Storm Warning from 6 AM this morning to 7 AM PST Saturday
     CAZ072.

&&

For more information from the National Weather Service visit...
http://weather.gov/reno