Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 181009

Area Forecast Discussion
National Weather Service Reno NV
309 AM PDT Fri Aug 18 2017


Thunderstorms remain a possibility each day through the middle of
next week. Storms this afternoon will again be mainly over the
Sierra, potentially becoming more widespread this weekend into
early next week but predictability remains about average. Flash
flooding will become more of a threat late this weekend and into
early next week. Temperatures through the weekend will remain
above normal with weak afternoon breezes each afternoon.



The main story over the weekend will be mid to upper 90 degree
heat across western Nevada (mid 80s for Sierra valleys) along
with increasing chances for thunderstorms across the Sierra.

The favored location for storms will again be across the northern
Sierra this afternoon were there is some modest increases in
moisture transport and instability. Storms motions are a little
tricky around the region as we will be centered in a COL region.
This means storms across the northern Sierra are expected to stay
along the crest with a slow southwest drift while any formation
across western Nevada could see storm motions slowly drift
eastward. Nonetheless, the slower storm motions may result in
isolated areas of heavy rainfall with gusty outflow winds

Coverage looks better heading into Saturday and Sunday as an
upper level shortwave trough digs southwest and begins to filter
in more moisture across the region. So far the most favorable
areas for showers and storms again will be across the Sierra and
far western Nevada as these ares will see southeast transport
which will increase moisture and help initiated storms across
elevated terrain. Also, these storms may not see the instability
and forcing that is expected by early next week, but the moisture
increase will begin to ramp up our threat for flash flooding.
Those with outdoor plans, particularly in the Sierra should
closely monitor the forecast for updates on thunderstorm
potential. Fuentes

.LONG TERM...Monday and beyond...

Looking busy next week with an eclipse, thunderstorms, increased
flash flood risk, and then ending with drier and breezy conditions.

The biggest question on the minds of many is the cloud cover
forecast for the solar eclipse Monday morning. Latest forecast
trends would suggest at least partly cloudy skies from remnant
thunderstorm debris, with odds about 60 percent. How much will this
impact the eclipse viewing is unknown as that will be highly
dependent on the exact position of the clouds in the sky at the time
of the eclipse, and that is nearly impossible to forecast. We`ll
continue to monitor the eclipse forecast and be sure to keep you up
on the latest details.

Otherwise, the large scale pattern for the early part of the week
features an area of low pressure sitting off the southern California
coast. This brings increased south to southeast flow to the eastern
Sierra and western Nevada helping to advect modified monsoonal
moisture northward. This will bring an increased coverage in
thunderstorms to the region Monday with Tuesday looking especially
interesting. On Tuesday, the low pivots, taking on a negative tilt
off the coast, with increasing upper level divergence aloft. PWATs
rise to around 0.8-0.9", which climatologically lends itself to
increased flash flood risk, especially given the light steering

Wednesday also could be another very active thunderstorm day as
upper level lapse rates increase, but there is one caveat. PWATs are
forecast to increase to 1-1.2", and frequently when they get that
high we start to cloud over and can`t realize the full instability
potential. This may be a wait and see type day where it could go big
or it may end up cloudy, cool, and showery with embedded isolated

Heading into the end of the week, the low off the southern California
coast weakens and is absorbed into the large scale flow as a
stronger area of low pressure dives through the Pacific Northwest.
This will bring drier westerly flow to the region and increased
afternoon breezes. There may be enough lingering moisture and
instability across central Nevada eastward for thunderstorms to form
on Thursday and with the increased shear, it may help bring some
organization to the storms. By Friday and into the weekend, storm
chances look minimal if not non-existent. -Dawn



Greatest threat for aviators will be isolated showers and
thunderstorms this afternoon, mainly along the Sierra and western
Nevada Sierra front. Storms are likely to form after 21z today,
dissipating between 03-05z. Brief periods of heavy rain, gusty and
erratic outflow winds can be expected with lesser chances for a hail
threat. Localized terrain obscuration is a concern along with short
periods of MVFR-IFR conditions under the rain core of the storms.
There is a 20 percent chance of a shower or thunderstorm impacting
KMMH, KTVL, an KTRK with a 10 percent chance for KRNO and KCXP.

Thunderstorm chances and coverage will increase through the weekend
and into the first half of next week.

Otherwise, expect VFR conditions over the weekend with afternoon
westerly breezes of 10-15 kts. If it rains at KTRK, the airfield is
likely to see fog develop overnight into the early morning hours. -


.REV Watches/Warnings/Advisories...


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