Area Forecast Discussion
Issued by NWS Reno, NV

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000
FXUS65 KREV 212158
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
258 PM PDT Tue May 21 2019

.SYNOPSIS...

Cool, showery weather, with periods of steadier precipitation,
will continue into the Memorial Day weekend. However, snow levels
are forecast to rise above 7500 feet from Wednesday evening onward
for diminishing snowfall impacts in the Sierra.

&&

.SHORT TERM...

Aside from increasing precipitation chances Wednesday/Thursday
and issuing a Lake Wind Advisory for Pyramid Lake during the day
on Wednesday as wind flow aligns with the lake`s major axis,
changes to the previous forecast were minimal. Low pressure will
influence weather conditions through Thursday with the long wave
trough remaining settled over the western United States for the
near future.

The main forecast challenge will be to time waves that move
around the low`s periphery. Currently, there are two impulses
that are expected to move through Wednesday and Thursday during
the day. These waves will bring higher chances of precipitation
with valley rain and higher elevation snow and snow showers. QPF
was increased marginally, but generally less than 0.05" for
valleys and less than 0.25" for higher elevations over Wednesday
and Thursday. Some models are trending wetter than this for
Thursday in higher terrain and we`ll be revisiting QPF amounts in
subsequent forecasts. With snow levels beginning to rise and the
daytime timing of moisture, accumulating snow for higher
elevations is unlikely. Still, there could be periods of
visibility reductions for those heading over Sierra passes. Boyd


.LONG TERM...Friday through Tuesday...

No major changes were made to the overall forecast, which will
feature a large and persistent area of low pressure residing over
CA-NV through the Memorial Day weekend. This low will keep cool,
cloudy and showery conditions over the region, with a slight chance
of afternoon thunder. In some areas, periods of steady rain could
potentially wash out outdoor activities, so anyone with outdoor
plans for the Memorial Day weekend should consider a plan B which
includes indoor alternatives.

While Friday will start out on the dry side, this low will begin to
make its presence known in the afternoon as it drops southward from
the Pacific Northwest, with showers and a few thunderstorms
developing over northeast CA/northwest NV, and more showers possible
near the Sierra. Then on Friday night, the first round of steady
rain looks to spread southward with the best chances from I-80
northward to near Susanville-Gerlach.

The most likely track of the low takes it south along the northern
CA coast Saturday, then the center moves offshore from central CA
Saturday night-Sunday before returning inland Monday across southern
parts of CA-NV. Even with the center of this low moving offshore,
areas of instability and enhanced lift associated with this system
are projected to set up over western NV and eastern CA. This will
lead to plenty of shower development with isolated thunderstorms
each afternoon from Saturday-Monday, with lingering areas of lighter
rain and high elevation snow continuing through the overnight hours.
With less cold air to work with compared to the current storm
system, snow levels in the Sierra will be mainly between 8000-9000
feet, but could dip to near 7500 feet early Sunday and Monday
morning. This would limit the risk of snow or slush on roads to
higher Sierra passes such as Carson Pass and Mt. Rose Summit during
the overnight and morning hours. Higher Sierra elevations above 9000
feet could receive a foot or more of total snowfall through the
holiday weekend.

Over the three day weekend, widespread precip totals of 0.50-1.00
inch are possible across much of eastern CA and western NV. Locally
higher amounts could occur in areas that receive more persistent
shower bands, or heavier rain during thunderstorms. While the
overall risk of flooding is low, smaller creeks and streams
especially near the Sierra could see significant rises with the
combination of heavier rain bands and melting of recent May
snowpack.

This low should finally exit the area next Tuesday, although below
average temperatures with chances for lighter rain showers will
continue. MJD

&&

.AVIATION...

A late-season storm system will continue to bring gusty winds of 25-
30 kt and mountain wave turbulence through this evening. Periods of
MVFR/IFR CIGS/VSBY with snow will continue through this evening at
KTRK/KTVL and into Wednesday morning at KMMH. For western NV, some
mountain obscurations are likely with -SHRA through this evening.

Active weather pattern continues Wednesday through the Memorial Day
weekend, with periods of MVFR CIGS, rain showers, and a slight
chance of afternoon thunder on most days. Milder temperatures will
result in rain as the precip type for Sierra terminals. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 1 PM to 8 PM PDT Wednesday for Pyramid
     Lake in NVZ004.

CA...None.
&&

$$

For more information from the National Weather Service visit...
http://weather.gov/reno


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