Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 272200

Area Forecast Discussion
National Weather Service Reno NV
300 PM PDT TUE SEP 27 2016


High pressure will begin to weaken Wednesday with a few showers
possible over southern Mono County. The ridge weakens further late
week as a trough of low pressure moves into the west coast. This
will bring breezy and cooler conditions to northeast California
and western Nevada.



Light winds continue through Wednesday with wind directions
determined either by terrain or a weak easterly gradient. For
Thursday, west winds pick up a bit as a Pacific trough approaches
the West Coast, with gusts 20 to 30 mph developing across ridges
and along the Sierra Front. These gusts will mix down to lower
elevations north of I-80 by Thursday afternoon.

Stronger and more widespread west winds develop Friday, with peak
gusts 30 to 40 mph by afternoon. Hazardous lake conditions are
likely, especially on Tahoe and Pyramid. For a discussion of
potential fire impacts due to these winds, see the FIRE WEATHER
section below.

A closed Low over southern CA/NV will weaken tomorrow as it tracks
into the eastern Great Basin Wednesday night and Thursday. Model
simulations remain consistent in keeping the deeper moisture
mostly south of Mono County and east of Mineral-Churchill-Pershing
Counties, with only a slight chance for showers over the White
Mountains and the Mammoth Lakes Area late Wednesday afternoon.
Instability will be weak so the risk for thunderstorms over these
areas is low (10%). Mid-to-high cloud cover associated with this
system could spread northward to near I-80 by Wednesday afternoon.

A dry cold front passes Friday night bringing cooler overnight lows
but no precipitation is expected. JCM

.LONG TERM...Saturday through Tuesday

Initial front/shortwave trough will be moving through Nevada
Saturday with instability/moisture staying northwest and well east
of our area. A dry and cooler airmass will move into the area with
mostly sunny skies. Breezy southwest to west winds will make it
feel quite cool as decent thermal gradients and mixing push
sustained surface winds to 20 to 25 mph with gusts generally
around 35 mph in the afternoon.

Confidence in the details lowers by early next week as both the
12Z GFS/ECMWF deterministic runs indicate a faster low amplitude
trough passage Sun-Sun night followed by some potential warm
advection cloudiness/precipitation Mon-Tue. There has not been
much run-to-run consistency. For Sunday, the breezy conditions
will likely continue with temperatures cooling a few more degrees.
Most of the light showers should remain across northeast CA and
northern NV with periods of clouds farther south as moisture
increases. Winds will result in a number of impacts over the
weekend including turbulence for aviators, rough lake waters for
boaters, and blustery conditions for the Sierra high country.

Monday-Tuesday, heights begin to rise although there are still a
number of simulations indicating a slower warmup aloft as well as
precipitation from a combination of warm advection and embedded
shortwave energy in northwest flow making it as far south as Hwy
50. We maintained a low chance of precipitation for these areas
with the caveat it could be a little wetter or drier than
forecast. Some scenarios are completely dry while others produce
some light snowfall/rain for the higher/lower elevations. Hohmann



VFR conditions with light winds through Wednesday. Winds increase
some Thursday with peak afternoon gusts around 25 kts. Stronger
winds are likely Friday bringing potential for moderate turbulence
above and in the lee of the Sierra by Friday morning. JCM



The incoming trough this weekend could create a few separate
periods of fire weather concerns Thursday through the weekend as
multiple cold fronts move through the region. Currently no period
stands out for a best combination of low RH and strong winds, but
there is the potential for at least localized critical fire
weather conditions.

Breezes will start to pick up Thursday as thermal gradients tighten
with gusts up to 25-30 mph expected. Very dry air will still be
in place on Thursday and localized critical conditions will be
possible in northern fire zones 278 and 458. On Friday a
combination of strong thermal gradients and good mixing to 30 kt
700 mb winds could create widespread gusts of 30-40 mph. Recent
simulations have backed off on the winds a bit and also show
enough moisture increase that we will hold off on issuing any
watch or warning headlines for Friday at this point.

Strong winds may continue to mix to the surface through the night
Friday and into the day on Saturday with the most likely area of
critical conditions likely shifting to the Western Nevada Basin
and Range. Sunday could also be quite windy but moisture should
have increased above critical thresholds by then. -Zach


.REV Watches/Warnings/Advisories...


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