Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 212212

Area Forecast Discussion
National Weather Service Reno NV
312 PM PDT Mon Aug 21 2017


Thunderstorms this evening for the Sierra and western Nevada will
bring localized heavy rainfall and gusty outflow winds. The
potential for flash flooding increases Tuesday with scattered
thunderstorms expected. Drier weather returns late week.
Temperatures will remain near or slightly above average through
the week.



Increased shower coverage to scattered and added a low chance for
thunderstorms late tonight and Tuesday morning in eastern California
from about Portola south, otherwise no major changes to the forecast.

Looking at satellite imagery, easterly flow aloft around the upper
low centered near the central/southern CA coast is quite evident
based on the motion of clouds. Forcing/convergence for convection
is strongest just west of the crest based on the thunderstorms
there and only weak development east of the crest so far. As we
go later into the afternoon and especially early evening, a few
showers and thunderstorms could form along and just east of the
crest due to local boundary interactions and convergence from a
possible weak westerly wind push in the northern Sierra. For
western NV, any activity should remain isolated and confined to
south of Highway 50. Storm strengths look similar to the last few
days, with gusty winds 30-40 mph and brief moderate-heavy rainfall.
A couple stronger storms are always possible and could bring hail
to 1/2" in diameter or slightly larger in very isolated

Late tonight, simulations are indicating the possibility for
nocturnal showers and possibly even a few thunderstorms south of
Interstate 80 as a disturbance (currently near the Lower Colorado
River Valley) works around the east side of the aforementioned
upper low. Elevated instabilities vary among simulations with more
chance for a few thunderstorms in the NAM than in the GFS. With
clouds on the increase tonight, low temperatures are expected to
be milder by 4 to 8 degrees than this morning in many locations.

Tuesday is still looking like the best day for thunderstorm
coverage as the region gets into a favorable area of divergence
aloft ahead of the upper low. Daytime heating should fire off
scattered thunderstorms in the eastern Sierra and for western
Nevada by early to mid afternoon. PWATs remain elevated in the
0.7" to 0.95" range and storm motions should remain mostly around
10 mph or less so localized heavy rainfall remains likely. Flash
flooding is not out of the question if heavy, persistent rain
falls on burn scars or areas where vegetation has been stripped.

Wednesday will feature one more day of isolated to scattered
showers and thunderstorms with localized heavy rainfall (slow
storm motions) before drier, more stable southwest flow aloft
invades for late Wednesday night and Thursday.

.LONG TERM...Friday through Monday...

Dry weather is expected Friday through at least Saturday before
flow aloft returns to southerly as high pressure builds over the
Great Basin. High temperatures should rise to at least 4 to 8
degrees above average with solid 90s for the lower valleys for the
weekend. The southerly flow and above average temperatures should
allow instability to begin building over the higher Sierra
terrain, with some cumulus buildups possible by later in the
weekend. With low potential coverage, thunderstorms were left out
of the forecast for early next week. -Snyder



Chances and most likely timing for a thunderstorm to impact or be in
the vicinity of a terminal site through 03-04Z this evening:

KRNO and KCXP: 5%
KTVL: 30-35%
KTRK: 15%
KMMH: 5%
KNFL and KLOL: 2%

Thunderstorms this evening could bring outflow winds to 30 kts,
brief heavy rainfall with higher terrain obscuration, and a few
lightning strikes.

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/Snyder


.REV Watches/Warnings/Advisories...


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