Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 170948
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
248 AM PDT Thu Aug 17 2017

.SYNOPSIS...

Light afternoon breezes and above average temperatures are
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...

We will remain between a broad shortwave trough and ridging
across the eastern Pacific with high temperatures warming above
season averages heading into the weekend. High temperatures
for western Nevada will reach the low to mid 90s into the weekend
with warmer valleys across the western Nevada basin and range
heating to the mid and upper 90s. Sierra valleys will reach into
the mid 80s.

The main focus in the short term is with the evolution of the
upper level shortwave low. Model guidance show this low digging
southwest into the weekend which would provide increase southerly
flow and moisture transport into the region. This pattern would
allow for increases in shower and thunderstorm coverage into
Saturday.

For this afternoon, coverage will remain confined mainly west of
Highway 395 and south of Highway 50 in eastern California as the
flow aloft remains light northwesterly. On Friday, the storm
steering flow is rather light so most storm formation is expected
to form over the Sierra and other high terrain across western
Nevada. Storm motion is rather slow so isolated areas of heavy
rainfall will be possible. Saturday, thunderstorm coverage will
expand as increased moisture and instability arrive across the
Sierra and western Nevada. There is some potential for modest
upper level forcing by late Saturday as a reinforcing shortwave
trough approaches the region. This could allow for longer lived
cells and an increased potential for heavy rainfall and hail
through early Saturday evening. Fuentes


.LONG TERM...Sunday through Wednesday...

Only very minimal changes were made to the extended forecast this
cycle.

Medium range models are continuing the trend of dropping a closed
low down the CA coast through the weekend that sits near the coast
through early Tuesday before starting to lift northeast. This leaves
much of our forecast area under upper level diffluence through
Tuesday before the low opens and lifts across the region as an open
wave.

Instability driven by daytime heating gets a boost from this upper
level diffluence...but if the low sets up too far off shore we may
not see as much thunderstorm coverage. Small scale forcing is also
key in this scenario. Where any mesoscale forcing develops we are
likely to see more coverage and/or stronger storms. This far out it
is still difficult to pinpoint exact areas where this forcing
develops so coverage was left fairly broad brushed over the region
Sunday through Tuesday.

Most activity should by in the afternoon and evening...but presence
of upper diffluence and embedded waves means the possibility of
showers overnight as well. Slow moving storms in this scenario could
also result in localized heavy rain by the end of the weekend into
next week.

As the upper low starts to lift out late Tuesday into early
Wednesday the models are showing southwest flow developing aloft.
This would mean less coverage Wednesday...mainly confined to areas
south of Highway 50.

&&

.AVIATION...

Weak north to northeast flow aloft in the wake of an upper trough
that has moved through the forecast area should mean less chance for
thunderstorms today...except in areas south of Alpine County along
the Sierra where upslope flow could generate a fews storms. Light
winds are in store for the terminals today. Gusty ridge winds of up
to 30 kt are possible this morning.

As we move toward the weekend expect shower and thunderstorm
coverage to increase each day. More storms are likely into early
next week.

Winds at the terminals this weekend will be fairly light as
well...except in the vicinity of thunderstorms.

&&


.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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