Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 172200

Area Forecast Discussion
National Weather Service Reno NV
300 PM PDT Thu May 17 2018


Low pressure over the Great Basin will bring another round of
showers and thunderstorms through this evening, then lift to the
northeast and reduce the thunderstorm threat for Friday. Another
low will settle over the region this weekend through at least the
middle of next week, increasing thunderstorm chances with locally
heavy rainfall possible, especially Monday and Tuesday.



Showers and a few brief thunderstorms have formed so far this
afternoon with most activity near and north of I-80 but south of
Susanville-Gerlach. Widespread cloud cover has limited shower
development farther north, although a shortwave rotating into
northeast CA/far northwest NV could still produce increased cell
coverage later today into this evening. Overall, we are not
expecting much intensity with these cells, although slow movement
could bring moderate rainfall amounts (about 0.10-0.25") to some
locations, mainly for Lassen/Plumas counties and possibly edging
into parts of the Tahoe basin and the Reno-Carson vicinity.

On Friday, residual moisture and surface based instability will
lead to cumulus buildups during the afternoon. Forcing looks to
be limited as most of the region will be in between the upper low
exiting the Great Basin and too far removed from the next low
approaching for this weekend. One exception is near the Sierra
mainly south of US-50 where a weak disturbance may provide a bit
more upper divergence to support scattered showers and
thunderstorms. We will continue to mention the best chances for
Alpine-Mono counties into southern Lyon and western Mineral
counties, with more limited coverage farther north including
Reno-Carson and Tahoe to Plumas County. With the increased
heating, a few cells could be stronger and produce small hail
accumulations, with slow cell movement and nearly unidirectional
flow aloft possibly producing some training cells with locally
heavy rainfall.

For Saturday, forcing increases as the next trough with a negative
tilt orientation moves into northern CA. This will lead to showers
and thunderstorms forming by midday along the Sierra and then
pushing off into western NV during the afternoon and evening.
There should be plenty of sun/heating early in the day to coincide
with cooling aloft to produce decent instability, while
increasing winds aloft/shear will increase the potential for
stronger and more organized storms. The best potential for these
enhanced storms currently favors Mineral-Lyon counties northward
into the Basin and Range, with a secondary area of increased
activity possible across the northern Lassen convergence zone.
While cells may move a bit faster compared to Friday, heavy
rainfall/flash flooding will become a concern with the more
intense cells, along with hail and strong outflow gusts. MJD

.LONG TERM...Sunday through next week...

An active weather pattern continues as multiple upper level lows
provide chances for showers and thunderstorms through the first half
of next week. Storms on Sunday look to focus along convergence zones
across northern Lassen and south toward Mono-Mineral counties.
Shower and thunderstorm coverage increases by Monday and Tuesday
with deformation forcing associated with the low descends along
western Nevada. The low looks to be slow to depart the region as it
absorbs and rotates another upper low descending from the Pacific
Northwest. This should result in continuing chances for
thunderstorms through mid-week.

The approach of the low will provide solid instability and column
moisture through mid-week but generally weak shear and steering
flow. As a result the main convective threat with these storms look
to be hail and areas of heavy rain and possible localized flash
flooding, with training storms possible. Fuentes



Showers and thunderstorms are expected this afternoon, with some
gusty outflow winds to 30 kts or so. Best chances of thunder
(about 30%) will be for KSVE and Reno-Tahoe terminals between 23Z-
03Z this evening, with lower potential (less than 20%) for KMMH
and other western NV terminals.

The thunderstorm threat continues this weekend, especially Saturday
and Sunday. Friday will have limited shower coverage over the Basin
and Range due to a small amplitude ridge moving into the region.
However, a thunderstorm threat will still remain for areas just east
of the Sierra crest. -Johnston/X


.REV Watches/Warnings/Advisories...



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