Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 302123

Area Forecast Discussion
National Weather Service Reno NV
223 PM PDT SAT APR 30 2016


Warmer temperatures are expected from Sunday through Tuesday with
a chance for showers and a few thunderstorms each afternoon and
evening, mainly over the Sierra. A return to cooler and
potentially much wetter conditions is possible starting Wednesday.


.Short Term (through Tuesday Night)...

Main forecast issue through Tuesday will be daily chances for
showers and few thunderstorms as weakening low pressure aloft
maintains an influence over the Great Basin. Overall impact
potential is low.

A rather cool, cloudy end to April today. Moderate thermal and
pressure gradients will keep gusty NE winds going over the region,
especially the ridges, through tonight. Those gradients are slowly
decreasing however, and valley wind gusts have generally remained
below 30 mph. Therefore we`ll be canceling the lake wind
advisories. Later tonight skies are expected to clear and even
with recent precipitation, boundary layer winds may stay up enough
to limit fog formation to just the favored valleys such as Truckee
and Loyalton. If winds subside more than expected, fog possible
even around Lake Tahoe and Stead/Spanish Springs.

With a trough overhead and slightly more warming with less cloud
cover tomorrow, airmass looks to destabilize Sunday afternoon and
evening especially over the Sierra. This should yield scattered
showers and thunderstorms. 3-6km AGL flow is mainly E/SE but light
so best risk of storms is near the crest and to the west. Snow
levels in latest guidance projected to be 8500-9500 ft but could
lower 1000 ft in storms - so some of the higher pass roads in the
eastern Sierra may get some light accumulations, perhaps further
delaying openings.

A few showers and storms are possible Monday and Tuesday over the
Sierra and immediate lee. However even with warming temperatures
instability signals are not overly impressive so coverage may be
isolated. Tuesday night, GFS generates a widespread area of rain
over the region ahead of this approaching trough. Perhaps the
first of what may be a few wet periods mid/late next week. ECMWF
is much drier so will maintain only low chances for showers
Tuesday night. -Chris

.Long Term (Wednesday through Saturday)...

A broad area of low pressure looks to impact our weather next
week with increasing confidence in a return to a cloudy and cooler
pattern. This low will be slow to move through the region so it
should provide prolonged chances of showers and isolated
thunderstorms into next weekend. Main changes to the forecast were
to continue a cooling trend with higher chances of precipitation
through Saturday.

Unlike recent low pressure systems, ensembles spreads and model
consensus has been well behaved with this low. This lends to
increasing confidence in the actually development of the low but
of course timing/details will become refined over the upcoming
days. Overall looking for this low to provide some dynamic forcing
by Wednesday but with increased cloud cover, instability may be
weak initially. Do expect some showers and perhaps isolated
thunderstorm activity Wednesday afternoon across far northeast
California, but precipitation coverage won`t become widespread
until Thursday as the core of the low moves across the central
Sierra. This will enhance instability with several hundred J/kg of
CAPE developing across the Sierra and western Nevada Thursday
through Friday.

As such, have maintained chances for showers and isolated
thunderstorms through Saturday with Thursday and Friday looking
like the most favorable days for thunderstorms. This low may also
be cold enough to provide snow showers for higher elevations
roughly about 7,000-7,500 feet so there is some chance to impact
higher passes and result in travel slow downs. Less confidence
exists for exact snow levels through the week as it depends on the
track and timing of the low. Fuentes



Breezy northeast winds will diminish this evening with areas of
light to moderate turbulence possible over the Sierra. Mountain
top obscurement will remain this evening across the Sierra but
cloud decks should lessen and lift through Sunday morning.
Decreasing clouds and winds coupled with recent precipitation
cloud produce areas of fog at KTRK tonight into Sunday morning.

Breezy northeast flow will again be expected on Sunday with the
possibility for rain showers and isolated thunderstorms mainly for
Sierra terminals (KTRK/KTVL/KMMH). Periods of IFR conditions are
possible within shower and storm activity with rapidly reduced
visibility, lightning, and small hail the main threats. Probability
for thunderstorms is about 15% for KTRK/KTVL and 20% at KMMH.


.REV Watches/Warnings/Advisories...


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