Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 210349 AAA
AFDREV

Area Forecast Discussion...UPDATED
National Weather Service Reno NV
849 PM PDT Sun Aug 20 2017

.UPDATE...
Storm coverage was less today to the east of the crest as easterly
flow was a bit stronger. One storm dropped some quarter sized
hail around the Emerald Bay area earlier this evening. Otherwise
storms were also a lot weaker compared to Saturday. The threat for
thunderstorms has diminished and we are expecting isolated
showers to linger this evening before ending overnight. Similar
conditions are still anticipated for Monday with 00Z model data
indicating an increase in coverage and intensity of storms for
Tuesday. Hohmann

&&

.PREVIOUS DISCUSSION... /Issued 325 PM PDT Sun Aug 20 2017/

SYNOPSIS...

A few thunderstorms are expected, mainly in the Sierra through
Monday, with increasing coverage Tuesday. Localized heavy
rainfall and gusty outflow winds are expected through Monday, with
an enhanced potential for flash flooding Tuesday as storm coverage
increases. Drier weather returns late week. Temperatures will
remain near or slightly above average through the week.

SHORT TERM...

Only minor changes to the short term forecast. Isolated to
scattered afternoon and evening thunderstorms are expected through
Monday, most widespread near and west of the Sierra crest as
steering flow remains easterly with the upper low off the southern
California coast. Most thunderstorms will be capable of brief
heavy rainfall, hail less than 1/2" in diameter, and gusty outflow
winds 30-40 mph.

As far as cloud cover Monday, timing will be critical for eclipse
viewing as simulations show increasing moisture and possible cloud
cover mid to late morning for Mono and Mineral Counties, with
perhaps some residual high clouds from this evening`s convection
farther north over the Highway 50 and Interstate 80 corridors. At
this time, it appears there is a good chance (70%) for viewing the
partial eclipse north of Highway 50 with only some minor high
cloudiness expected. However, chances drop some (40-50%) south of
Highway 50 with simulations showing the moisture/cloud surge
between 8-11 AM.

Mid-level moisture and cloud cover increases Monday night and
Tuesday as western Nevada and the eastern Sierra get in the upper
divergent area between the upper low off the California coast and
an upper ridge near the Nevada and Utah border. With the increased
moisture and at least weak upper forcing, a slight chance of
showers was kept for much of the area Monday night and/or Tuesday
morning. Instability is not too impressive in simulated soundings
so thunder was left out for the overnight-morning period.

Tuesday afternoon and evening still looks like the best time
period for thunderstorm coverage as PWATs edge up to between 0.7"
and 1" and the region remains in divergent flow aloft ahead of the
upper low. With the increased thunderstorm coverage expected,
there will be an increase in the threat for heavy rainfall and
localized flash flooding, mainly for burn areas and in areas of
steep terrain denuded of vegetation (such as construction sites).

Wednesday, there will still be isolated to scattered thunderstorms
although they will tend to nudge off the Sierra crest by early
evening as flow aloft begins to turn more southwest to west aloft.
-Snyder

LONG TERM...Thursday through Sunday...

Drier and more stable west to southwest flow aloft returns late
week as low pressure moves into the Pacific Northwest. By next
weekend, temperatures edge up to 3-6 degrees above average as
high pressure strengthens overhead. At this time, it looks too
stable for thunderstorms next weekend. Snyder

AVIATION...

Scattered showers and thunderstorms are most likely over the Sierra
into the evening, with isolated storms across far western Nevada.
The easterly flow will help storms that do develop slowly drift
westward; however, outflow boundaries can cause storms to deviate
from the overall flow. Brief heavy rain and gusty and erratic
outflow winds to 30-35 kts can be expected, with lesser chances
for hail up to 1/2" in diameter. Storms should dissipate by around
8-9 PM.

Thunderstorm chances and coverage look fairly similar on Monday as
today with an increase on Tuesday.

Outside of thunderstorm-influenced environments, expect VFR
conditions with afternoon westerly breezes up to 8-10 kts. Early
morning patchy fog for Monday remains possible around KTRK if the
airfield receives rainfall. 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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