Area Forecast Discussion
Issued by NWS Reno, NV

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447
FXUS65 KREV 220345
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
845 PM PDT Wed Jun 21 2017

.UPDATE...

Convection is decreasing across western Nevada this evening and
has ended in the Sierra. A few showers and storms are hanging on
from Lyon County east into the far northern part of Mineral
County and eastern Churchill County. This activity is associated
more with a weak trough that has focused the activity since about
630 pm. With the loss of heating we should see the activity end by
around 10 pm.

LAtest model guidance is in line with the previous guidance and
shows activity developing again Thursday...but covering a smaller
area mainly in the Sierra.

Updates will be out shortly.

&&

.PREVIOUS DISCUSSION... /Issued 246 PM PDT Wed Jun 21 2017/

SYNOPSIS...

High pressure will bring much above average temperatures through the
weekend, with cooler temperatures possible next week. Isolated to
scattered thunderstorms are expected today near and south of
Interstate 80, with isolated storms in Mono County Thursday through
Saturday. Flooding will continue for the creeks and streams in
Mono County and for portions of the Walker River.

SHORT TERM...

A weak upper trough axis is dropping south through western NV and
the northern Sierra this afternoon. This, along with a weak surface
trough extending through Mono/Mineral Counties, is providing focus
for developing convection this afternoon. So far convection remains
meek but this is expected to change as heating maximizes into the
early evening. Recent HRRR runs have pegged the initial cell
locations (eastern Mono County and out in central NV) better than
the NAM/GFS.

The HRRR shows isolated showers and thunderstorms congealing into
scattered coverage this evening south of Highway 50 in western NV
and over eastern Churchill County...with activity moving north
(likely on outflows from earlier storms). Still, while confidence
in the HRRR is growing due to its fairly consistent and so-far
accurate depiction of convective location, steering flow is very
light so storm motion will be driven by smaller-scale features
such as storm outflows. These can be quite chaotic and unpredictable.
Therefore, a broad-brush approach to evening storms (especially
north of Highway 50) was taken to allow for possible locations for
evening showers and thunderstorms. In any case, large surface
temperature-dewpoint spreads should once again allow for storm
outflow wind gusts over 50 mph out in the Basin and Range, with
areas of blowing dust possible. As far as rainfall, with light
storm motions stronger storms will be capable of dropping cores of
moderate rain, although they could be rather narrow with the dry
lower levels evaporating much of the precipitation on the edges
of storms.

Thursday, the upper level trough axis will move south into the
central Sierra and the southern half of Nevada. This is expected
to kick the focus for showers and storms down into Mono County and
points south for a quieter day as far as afternoon showers and
thunderstorms.

Friday, the upper ridge settles back overhead for a rising temperature
trend once again. With well above average temperatures and only
minor subsidence aloft a few thunderstorms cannot be ruled out in
the higher terrain near the Mono County crest. Therefore, a slight
chance of storms was added to the forecast there.

Over the weekend, the strong upper ridge remains overhead for highs
well above average...in the mid 90s to low 100s for lower valleys
and mid 80s to lower 90s for Sierra valleys. Thunderstorms will
continue to be possible with daytime heating in Mono County both
days. However, on Sunday simulations are also beginning to show
convection spreading into northeast CA and western NV as a weak
impulse moves into northern CA (and induces a zephyr) on the
periphery of the upper ridge. This makes sense and is shown in
many simulations so storms were expanded out into western NV and
up into northeast CA.

LONG TERM...Monday through Wednesday...

Next week, models continue to show a weakening of the upper ridge
for an end to thunderstorms, increasing breezes, and a gradual
cool down towards average high temperatures. Snyder

Fire Weather...

Another very hot and dry day today with thunderstorms developing
this afternoon and moderate to poor mid slope recoveries for the
next several nights. Thunderstorms are currently forming over the
high Sierra in Alpine/Mono Counties and may move into the Sierra
Front and the Basin and Range during the late afternoon/early
evening along gust fronts from the initial thunderstorms in the
Sierra. Thunderstorms should generally be of the wet variety since
storm motions are expected to be slow, but lightning strikes can
always happen outside of rain cores.

Winds will be generally light out of the north today until
thunderstorms form, then a quick change to south winds will be
possible with gusts of 40 to 50 mph along thunderstorm outflows.
Localized Red Flag conditions could easily occur for 1-2 hours as
the gusts fronts from thunderstorms move into western Nevada.

Hot and dry conditions are expected over the weekend with afternoon
thunderstorms a possibility each day, however, storms are expected
to be more confined to the Sierra after today. A trough is forecast
to approach the west coast early next week which would cause an
increase in thunderstorm activity and increased potential for
critical fire weather conditions Monday and/or Tuesday as winds
increase. -Zach

AVIATION...

&&

.REV Watches/Warnings/Advisories...
NV...None.
CA...None.
&&

$$

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



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