Area Forecast Discussion
Issued by NWS Reno, NV

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713
FXUS65 KREV 221114
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
307 AM PST Thu Feb 22 2018

.SYNOPSIS...
Below average temperatures will dominate through at least next week
as low pressure remains over the West. A series of systems will
bring the threat for snow, with the first bringing a widespread
light to moderate snowfall today. Most areas will see a break Friday
through the weekend, with another system expected Monday into
Tuesday of next week.
&&

.SHORT TERM...

SUMMARY OF IMPACTS THROUGH TONIGHT:

* Burst of snow (periods with snowfall rates up to 2 inches/hour
  possible) for the western Nevada morning commute today.
  RAPIDLY DETERIORATING CONDITIONS EXPECTED after 6AM with periods
  of very low visibility and local white out conditions.

* Local snowfall amounts to 6 inches in lake-effect snow bands
  south and southeast of Lake Tahoe and Pyramid Lake, including
  Douglas and El Dorado Counties and between the Tahoe-Reno
  Industrial Center and Fernley.

* Evening commute issues due to flash freezing of wet afternoon-
  evening roads and continued snow showers this afternoon.

* Wind chills to -20F in the high Sierra today.

Main changes were made to adjust QPF and snow amounts upwards for
the Sierra for this afternoon and into tonight. Latest model
simulations have trended a bit further west with the secondary wave
of snow for this afternoon. Although we will likely still see some
snow shower across western Nevada, there is a greater chances for
meaningful snow amounts in the Sierra from Tahoe southward into Mono
county.

Otherwise the overall impacts associated with this slider remain the
same: snow will impact the morning and evening commutes today, lake
effect snows will likely develop south and east of Tahoe and Pyramid
with additional snow accumulations possible, and dangerous wind
chills will affect the high Sierra. Be sure to leave plenty of time
for the morning and afternoon commutes today.

Peak snowfall rates for this morning should occur between 6am-10am
with 1 to 3 inches of accumulation possible. Snow rates will be
around 2 inches/hour, which will decrease visibility
significantly and result in quick accumulations during the morning
commute. The snowband is showing hints of slowing down and
stalling near Interstate 80, which would result in additional snow
accumulations. In this scenario upwards of 6 inches of snow could
be possible for areas north of Interstate 80. Keep in mind that
only an inch of snow can result in major traffic headaches and
increased accidents since the snow can be compacted quickly and
refreeze. Even though more snow could provide better traction,
just plan on slowing down and taking extra care while driving
today.

Snow showers will continue through the afternoon across the Sierra
and western Nevada. A secondary wave will drop along the Sierra
which will result in another round of increased snow rates. We went
ahead and increased the snow amounts for the Sierra to account for
this more westward track of the secondary wave this afternoon. It is
also still looking good for the lake effect snow to fire up off area
lakes this evening and tonight. Less shear and plenty of instability
overnight will coincide with the climatologically prime time for
lake effect snow development, especially off of Lake Tahoe and
Pyramid Lake. Lake effect snow accumulations could range anywhere
from an additional 2-4 inches to up to 12 inches. This is completely
dependent on the strength of the convective snow showers that
develop. Areas and communities south and east of Tahoe and Pyramid
Lakes shouldn`t be completely caught off guard to see much higher
snow amounts than surrounding areas by Friday morning.

Upslope snow showers may persist south of Highway 50, especially
for Alpine and Mono counties on Friday morning, but otherwise
Friday will be a chilly, brisk north wind kind of day. On Saturday
another wave will drop across Nevada which may bring another
round of showers as far south as Highway 50 by Saturday night. The
best forcing for this next wave will be east of the region, but
either way it is another reinforcing shot of cold air with snow
showers. -Edan

.LONG TERM...Sunday and beyond...

We continue our active winter weather pattern through the rest of
February and into the first half of March. Pretty exciting to see
active winter weather back into our region after such a warm and
dry winter. The East Pacific ridge remains around 150W through the
first half of March keeping the storm door open across the
western U.S. as multiple shortwaves drop out of the Gulf of
Alaska.

The next storm system will move through the area on Monday-
Tuesday, with a bit further offshore track that would be able to
pick up a little more Pacific moisture before moving into the
Sierra. This wave will bring another reinforcing shot of cold air,
along with snowfall with the incoming cold front. Snow levels
will be down to all valley floors Monday-Tuesday, with the Monday
evening commute most likely impacted by snow. The ECMWF shows a
bit more of a deformation band of snow Monday night into Tuesday
morning, so we`ve increased chances for snow during that time.

We get a little bit of break Wednesday, but then models continue
to show another storm system to come into the Sierra and western
Nevada by Thursday-Friday with more snow and reinforcing cold air
across the region. This storm late next week so far has looked
like the most impactful storm of this series, so we will need to
keep a close eye on it. Bottom line--if you have travel plans
anytime next week, please keep up with the latest forecast,
because winter impacts will be likely for periods through the
first half of March. -Hoon

&&

.AVIATION...

The next storm system/cold front moves into the region this
morning, bringing widespread light to moderate snow to the region,
including the lower elevations in northeast CA and western
Nevada. Breezy winds along the front, along with moderate snow
will bring periods of MVFR/IFR CIG/VIS and widespread terrain
obscuration to area terminals, especially north of KO57
(Bridgeport) and KHTH.

After a break for a few hours after the frontal passage, additional
snow showers will develop this afternoon and evening, although
pinpointing where the heavier snow showers and major reductions to
CIGS/VIS will be is of low confidence. The only exception will be
south and southeast of Pyramid Lake and Lake Tahoe where lake effect
snow bands could develop.

Storm total snow amounts for KTRK-KTVL will be around 3-6 inches,
with about 1-3 inches expected for KRNO-KCXP, and up to 2-3 inches
for KMMH. Snow accumulations are also likely for KNFL-KLOL with
up to 1-2 inches possible. -Snyder/Hoon

&&


.REV Watches/Warnings/Advisories...
NV...Winter Weather Advisory until 7 PM PST this evening NVZ005.

     Winter Weather Advisory from 7 AM this morning to 4 AM PST
     Friday NVZ001.

     Winter Weather Advisory until 10 PM PST this evening NVZ002.

     Winter Weather Advisory until 10 PM PST this evening NVZ003-004.

CA...Winter Weather Advisory until 7 PM PST this evening CAZ070-071.

     Winter Weather Advisory from 7 AM this morning to 4 AM PST
     Friday CAZ073.

     Winter Weather Advisory until 10 PM PST this evening CAZ072.

&&

$$

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



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