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fxus65 krev 212151 
afdrev

Area forecast discussion
National Weather Service Reno Nevada
151 PM PST Thu Nov 21 2019

Synopsis...

There will be a warming trend going into the weekend with limited
ventilation due to inversions. An active weather pattern is likely
next week with colder storm systems bringing periods of snow, even
in lower valleys, which will produce impacts for Thanksgiving Holiday
travel.

&&

Discussion...

Highlights:

* snowy Thanksgiving travel is looking probable. While exact
details still need to be sorted out, the storm will be cold
enough for snow down to valley floors, and for an extended
stretch of all trans-Sierra roadways (not just the passes).

* At this point the best travel days look like Monday into early
Tuesday and then again on Thanksgiving. The weekend is still up
in the air so stay tuned.

* Being that this is a very busy Holiday travel period, significant
travel delays are possible with any amount of snow. Please monitor
the latest forecasts and plan ahead if you have travel plans for
Thanksgiving.

Ridging is looking likely going into the weekend with high
temperatures warming to near or slightly above normal with dry
conditions. Inversions will develop with limited ventilation. This
also means that valleys will be colder than many midslope and ridge
locations overnight.

Simulations continue to show a weak system dropping into the
intermountain west on Monday, flattening the ridge and bringing
northwest flow to the area. The most likely impacts will be increased
northwest winds and cloud cover, with low end chances for precipitation
mainly near the Oregon border and into central and eastern Nevada.
This system opens the door for a more significant system Tuesday into
Wednesday.

A cold winter storm is looking likely to impact the region Tuesday
into Wednesday. Simulations are consistent in how cold this storm
will be with 700 temps in the -12 to -15 c range. This means snow
levels could easily drop to 2000 feet, leading to a long stretch of
all Sierra roadways being potentially snow covered during one of the
busiest travel periods of the year. Liquid totals, and subsequently
snow totals, have been varying, but the trend has been wetter.
Probabilistic data is indicating the potential for decent liquid
totals which aligns with ensemble data as well.

Longer range simulations favor the colder and wetter trend continuing
into the weekend following Thanksgiving but details are nebulous at
this time. The potential for additional storms is there but a wide
range of timing and location details exists.

The main takeaway is this: if you have travel plans for Thanksgiving
please pay attention to the latest forecasts so you aren't caught
off guard. Major travel delays both on the Road and in the air are
possible given the anticipated snowfall and increased Holiday traffic.
-Dawn

&&

Aviation...

Residual moisture wrapping around low pressure centered near klas is
bringing mainly VFR (isolated spots of high MVFR decks) cloud decks
along with pockets of higher terrain obscuration to western and west-
central Nevada. Meanwhile, sunny to partly cloudy skies are observed
for the Sierra and northeast California.

VFR conditions and light winds are expected for terminals Friday
through the weekend as high pressure builds overhead. The only
exceptions will be in the Martis Valley around ktrk where a return
to typical late night and morning freezing fog is likely and, for
the Carson Sink (including klol/knfl), a low (~20-30%) chance for
areas of fog for the next couple nights.

Stay tuned for next week: it will turn stormy and colder with
substantial snow and IFR conditions likely in the Sierra starting
late Tuesday into Wednesday. For the Lower Valley terminals in
western and west-central Nevada, snow is becoming increasingly
likely as well; however, snowfall amounts are quite uncertain at
this time. -Snyder

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Rev watches/warnings/advisories...
Nevada...none.
California...none.
&&

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