Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 170331 AAA
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
831 PM PDT Wed Aug 16 2017

.UPDATE...
Thunderstorms around the Tahoe Basin have ended with only few
showers/sprinkles lingering near the crest and south of Hwy 50.
Thunderstorms put down some decent rain on the west side of the
Tahoe Basin with a couple of gauge reports including 0.75 inches
around Tahoe City and 0.47 inches near Homewood. We will be
updating to remove chances for showers/thunderstorms for the
remainder of the night as a more stable northerly flow prevails.
Hohmann

&&

.PREVIOUS DISCUSSION... /Issued 235 PM PDT Wed Aug 16 2017/

SYNOPSIS...

Mainly light winds with temperatures near or slightly above
average is expected into next week. A few afternoon and evening
thunderstorms will be possible near the Sierra south of Highway 50
through Thursday. Thunderstorm coverage will expand across the
rest of the Sierra Friday, and into northeast California and
western Nevada for the weekend into early next week.

SHORT TERM...

Minimal change to the forecast through Saturday.

Easterly flow aloft has kept thunderstorms confined to just west
of the Sierra crest so far today, with a few outlier showers over
eastern Mono County and far eastern Pershing/Churchill Counties.
Most deep convection (thunderstorms) should remain near or west
of the crest today; however, very isolated storms cannot be ruled
out (due to small-scale forcing/convergence) as far east as
Highways 395 and 89 in the Sierra through around sunset.

Thursday should feature isolated showers and thunderstorms once
again. Flow aloft will remain northeast to east, so any storms
should remain west of Highway 395 and south of Highway 50 in
eastern California. However, by Friday flow aloft becomes very
light so a few storms could eek a bit farther north and east by
evening, possibly to near the California-Nevada border and up into
Sierra and Plumas Counties. Thunderstorms will not have any
large-scale help (shear or strong instability) to increase
intensity on Friday so they will rely on small-scale, unpredictable
forcing for their intensity. Therefore, most storms should remain
modest with outflow winds to around 35 kts, brief heavy rain, and
a few lightning strikes.

Saturday, GFS/NAM simulations show an increase in westerly flow
aloft, especially from Tahoe north, as a weak trough moves over
Oregon and far northwest California. This is shown by those models
to nudge convection off the crest north of Highway 50. As this was
already indicated in the forecast, POP was largely left alone for
Saturday. Snyder

LONG TERM...Sunday through Wednesday...

Sunday into Monday, low pressure is simulated to drop along the
California coast. Monday through at least Tuesday, the low is
expected to hang out near the central and southern CA coast,
putting eastern CA and western NV in divergent flow aloft. This
will favor continued rounds of isolated to scattered thunderstorms,
mainly during the afternoon and evening but possibly continuing
overnight depending on any minor waves moving around the upper
low. At this time, storm motions appear slow so the threat for
localized flash flooding (especially downhill from burn scars and
in steep terrain) will increase over the weekend into early next
week.

As far as the partial eclipse Monday morning, there is a
low to moderate chance that partly cloudy skies will prevail by
Monday with residual convective clouds and general divergence
aloft favoring at least some clouds. That`s all we can tell you
for now so stay tuned if you plan on watching the eclipse.

Temperatures should be moderated by clouds and convection early
next week so near or even slightly below average temperatures are
expected. Snyder

AVIATION...

Afternoon and evening thunderstorms are expected to remain near
or west of the Sierra crest and south of Highway 50 through
Thursday, with a 5-10% chance for a storm at KTVL and 15-20% at
KMMH. Storms look relatively weak with outflow winds to 35 kts, a
lightning strike or two, and brief light rain possible.
Valley/terminal winds should remain generally less than 10 kts
from a northwest to northeast direction through Thursday.

Friday, isolated thunderstorms are forecast to creep farther north
and may drift to near the California-Nevada border by evening.
This will bring an increase (but still low) in storm chances for
KTVL/KTRK, with a storm or two within sight of KCXP/KRNO possible
(over Carson Range).

As far as significant reductions in visibility (both horizontal
and slantwise) due to wildfire smoke, the flow pattern and HRRR
smoke forecasts suggest that smoke/haze will be kept along and
west of the Sierra crest through Friday. Snyder

&&

.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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