Area Forecast Discussion
Issued by NWS Reno, NV

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115
FXUS65 KREV 210959
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
259 AM PDT Mon Aug 21 2017

.SYNOPSIS...

Showers and storms will develop again this afternoon across the
Sierra and portions of western Nevada. Localized heavy rainfall
and gusty outflow winds are expected with these storms this
afternoon. The potential for flash flooding increases on Tuesday
as storm coverage increases. Drier weather returns late week.
Temperatures will remain near or slightly above average through
the week.

&&

.SHORT TERM...

Latest IR satellite imagery shows mostly clear conditions across
the region with a few patches of mid clouds from the Tahoe Basin
through the highway 50 corridor. In regards to eclipse viewing,
cloud cover this morning overall will be mostly clear to partly
cloudy depending on your area. Southern Mono and Mineral counties
should see some spotty clouds this morning but should see these
clouds increasing after 10-11am. Less cloud coverage is expected
roughly north of highway 50.

This increase in clouds is associated with the lead edge of moisture
being drawn up from the south as an upper low approaches the region.
As such, we will continue our chances for afternoon showers and
thunderstorms through Wednesday before drying out for the remainder
of the week.

For today, shower and thunderstorm development will be favored near
and west of the Sierra crest as steering flow remains easterly with
the upper low off the southern California coast. The easterly flow
will also help transport storms initiating over southern Nevada
into southern Mineral and Mono counties by late afternoon.
Thunderstorms will be capable of brief heavy rainfall, hail
1/2"-1" in diameter, and gusty outflow winds of 40+ mph.

Tuesday afternoon and evening still looks like the best period for
thunderstorm coverage as column moisture increases to between 0.7"
to 1" and the region remains in divergent flow aloft ahead of the
upper low. The increased thunderstorm coverage and slower storms
with a more unidirectional shear will increase the threat for
heavy rainfall and localized flash flooding, mainly for burn areas
and in areas of steep terrain. New fire starts from lightning
strikes will be possible but the good news is that storms look to
be good rain producers with wetting rains expected.

Wednesday, isolated to scattered thunderstorms will remain but flow
aloft will begin to develop a westerly component which will aid in
moving storms off the Sierra crest by early evening. This will also
usher in a dry air mass which should end storm activity by mid-
evening. Fuentes

.LONG TERM...Thursday and beyond...

A trough shifting through the Pacific Northwest on Thursday will
bring dry westerly flow to the eastern Sierra and northwest Nevada.
A few showers may linger across north central Nevada early
Thursday morning, but by afternoon the region should be clear of
any precipitation. Typical westerly afternoon breezes are likely
on Thursday with lighter winds heading into the weekend.

For the weekend, a strong area of high pressure builds over the west
bringing temps 5-8 degrees above normal. The latest MEX guidance
suggests triple digit heat is possible for many western Nevada
valleys, however it has tended to have a warm bias this summer. A
better consensus is highs in the mid 90s for western Nevada valleys
and 80s in Sierra valleys over the weekend.

The atmosphere appears to be too dry and stable to support
thunderstorm development over the weekend, however would not be
surprised to see a few clouds popping over the Sierra. Going into
the early part of next week, moisture and instability begin to
increase with thunderstorm chances likely to return. -Dawn

&&

.AVIATION...

Scattered showers and thunderstorms will once again develop this
afternoon and evening with the greatest risks being heavy rainfall,
gusty and erratic outflow winds, and small hail. Localized terrain
obscuration is a concern along with short periods of MVFR-IFR
conditions under the rain core of the storms. The easterly flow will
help storms that do develop slowly drift westward, however outflow
boundaries can cause storms to deviate from the overall flow.

Chances and most likely timing for a thunderstorm to impact or be in
the vicinity of a terminal site:

KRNO and KCXP: 10 percent, 22z-03z
KTRK and KTVL: 20 percent, 21z-04z
KMMH and KBAN: 35 percent, 21z-04z
KNFL and KLOL:  5 percent, 23z-04z

The greatest thunderstorm coverage is anticipated to be on Tuesday
afternoon and evening with additional storms possible on
Wednesday. Storm chances will wane Thursday into the weekend with
typical westerly afternoon breezes. Conditions will be VFR outside
of thunderstorms. Early morning patchy fog remains possible
around KTRK if the airfield receives rainfall. -Dawn

&&

.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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