Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 131034
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
234 AM PST Thu Dec 13 2018

.SYNOPSIS...

Light winds and weak inversions return today. A system will bring
light high elevation snowfall for northeast California, with
strong and gusty winds for lower elevations Friday. Another
system late Sunday could bring higher elevation snow with travel
impacts for northeast California and the Sierra. Quiet, dry
weather is expected to persist for some time after Monday.

&&

.SHORT TERM...

Main changes: Raise high wind watch for the eastern Sierra and
northwest NV Friday. Raised temperatures today and especially
Friday. Lowered humidity levels from Sierra Front southward
Friday.

An upper ridge will build across the region today with warming
temperatures aloft and weak inversions developing. Winds will be
light and temperatures a few degrees cooler for most valleys this
afternoon.

The next shortwave trough will push through the Pacific Northwest
where most of the moisture will reside. Some light precipitation
will move into northeast CA and far northwest NV late Friday for
perhaps a few inches of snow above 5500 feet mainly from Plumas
and Sierra Counties northward Friday night with little spillover
into western NV. Snow potential is looking even less likely for
the Tahoe Basin where some very light amounts are possible Friday
night. We removed the chance altogether farther south across Mono
County.

The main impact from this system will be the wind. Surface
gradients tighten across northeast CA and northwest NV with 700 MB
flow ramping up to 50-60 kts by Friday afternoon. Clouds will
initially limit warming/mixing Friday morning except for the Tahoe
Basin and northeast CA/northwest NV where gradients will tighten
enough to get winds started early in those areas. Winds/mixing
will increase during the afternoon as temperatures warm ahead of
incoming trough, and thus expect surface winds to increase and
spread farther south and east to encompass much of the eastern
Sierra to about Highway 95. Sustained winds 20-30 mph with gusts
40-50 mph are likely Friday afternoon with a short period of
gusts approaching 60 mph. We will hoist a watch for potential high
winds and let the day crew take one more look at model data to
determine the exact impacts. Regardless, there will be impacts
for boaters on area lakes, high profile vehicles and aviation.
Farther east across the Basin and Range, there is still some
uncertainty how deep the mixing will be as inversions remain a bit
more stubborn. These areas should mix briefly and conditions will
become breezy.

Temperatures will warm to above normal levels Friday afternoon
with 50s for most valley areas. It will also start out quite dry
along the Sierra Front southward into eastern Mono County with
humidity dropping below guidance and into the teens to lower 20
percent range. Wind will decrease Saturday and allow for weak
inversions and slightly cooler temperatures once again although
there is not a lot of cold air associated with the system moving
across the region Friday/Friday night. Hohmann

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

The focus continues to be on the system moving through late Sunday
into early Monday. Overall changes for this cycle were to increase
the threat of rain/snow in the Sierra Sunday night into Monday
morning, but trim the threat back Sunday and Monday afternoon. This
is a result of the models in better agreement even with a bit of
split solution.

The EC continues to be a little wetter and not as splitty, but the
GFS/FV3 are a bit wetter with the split progressing through Monday
morning before diving southeastward. It looks a high PoP/low QPF
event for the Sierra with some precip falling Sunday night. As a
rough estimate, about 1/2 inch for the Sierra Crest near Tahoe and
1/3 inch for Mono County. Snow levels look to average near 6000
feet. With south flow aloft, spillover is not favored and
amounts/PoPs drop off rapidly east of the 395 corridor. The
Surprise Valley could be an exception up near the Oregon Border.

After this trough moves through, a moderate amplitude ridge will
build in with mild temps aloft. I have warmed temps for next week a
good 10 degrees above average. While inversions will be present in
the lower valleys, they will not be strong as the past week. Skies
will also be mostly clear during the day. Past mild ridges have put
55-60 degrees around Reno/Carson, but with the lowest sun angles
close to the winter solstice, kept it at the lower side of this
range.

Looking ahead, the ridge does look to go through some evolution and
it could remain dry into next weekend. After that, predictability of
the pattern so far this winter has been very low. Ensembles and even
the deterministic models (flip flops between trough/ridge) show the
low predictability ideas. X


&&

.AVIATION...
VFR conditions to continue through 12Z Friday. Winds will be light
today, but begin to increase tonight over the ridges with gusts to
50-60 kts after 06Z and mtn wave turbulence increasing. Friday will
be windy most areas west of the Highway 95 corridor with peak gusts
of 40-50kts possible for the terminals (strongest at KRNO/KRTS).
Mtn wave turbulence and pockets of LLWS will be present with LLWS
most likely near KTRK/KTVL/KRNO/KCXP. Winds will diminish after 03Z
Saturday. A few showers are possible near the Oregon Border with
local MVFR CIGS/VIS.

Sunday winds will increase again, but peak gusts will be less,
perhaps 30 kts at area terminals. MVFR/IFR CIGS/VIS are likely in
the Sierra Sunday night with -SNRA. X

&&


.REV Watches/Warnings/Advisories...
NV...High Wind Watch from Friday afternoon through Friday evening
     NVZ002-003-005.

CA...High Wind Watch from Friday afternoon through Friday evening
     CAZ070>073.

&&

$$

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


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