Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 252136

Area Forecast Discussion
National Weather Service Reno NV
236 PM PDT Sat Mar 25 2017


Another spring storm will move across the Sierra and western Nevada
Sunday into Monday with travel impacts possible for the Monday
morning commute in the Sierra. Breezy winds may create choppy lake
conditions through the weekend. After a weak storm on Thursday
the pattern appears to trend drier and warmer for the end of next
week and next weekend.



Low pressure is exiting the area this afternoon with only a few
light showers lingering due to the instability aloft. Shower
activity will taper off late this afternoon as the sun starts to
set and we lose daytime heating.

Another wave moves into the region Sunday into Monday, bringing
increasing winds once again and mountain snow. Very few changes
were made to the forecast, mainly to slow down the precip Sunday
and bring lower snow levels for Northeast CA Sunday night into
Monday morning.

Weak warm air advection will move into the area during the day on
Sunday with increasing clouds and very little precipitation.
Models have definitely trended drier with this system, especially
during the day on Sunday with mostly just clouds and a few
sprinkles/flurries expected. By Sunday night, the main shortwave
and cold front moves through the Sierra, bringing a period of
moderate to snow to elevations mainly above 6000 feet. There is
some colder air coming in Sunday night behind the front, which may
bring snow levels down to near 4500 feet in northeast CA (closer
to 5000-5500 feet around Reno-Tahoe). The best time to travel
over the Sierra will be Sunday during the daylight hours. After
6pm Sunday, snow will begin to push into the Sierra, causing
travel delays.

Even though the models have continued to show less precip for
Sunday night/Monday, we should still be able to see several inches
of snow in the Sierra valleys by Monday morning and up to 5-7
inches at pass level above 7000. The Monday morning commute in the
Sierra will be impacted by slow, snow covered roads with travel
delays likely. We could even see some light snow into western
Nevada above 5500 feet, including Virginia City. As for the
majority of western Nevada (below 5500 feet), we should see a
period of light to moderate rain spillover and wet roads Monday
morning, but not expecting any major impacts for the lower
elevations. Winds will become breezy by Sunday afternoon as the
front approaches the area.

Once this trough pushes over the region, we will see cooler
temperatures on Monday with a brisk north wind behind the cold
front. A few light showers will continue for areas south of
Highway 50 on Monday afternoon due to cold air instability aloft.
Temperatures will bounce back several degrees warmer on Tuesday,
along with lighter winds as ridging builds back into the West
Coast. Hoon

.LONG TERM...Wednesday through Saturday...

The latter half of the upcoming week looks more interesting as
medium range guidance sources present the possibility of a cold low
pressure dropping south into Nevada on Thursday. Cool north to
northeast flow could continue into Friday before a warming trend
returns for next weekend.

For Wednesday, little change was made to the current forecast. Upper
level ridge is projected to become flatter with weak shortwave
energy brushing across the Pacific Northwest. The main effect will
be increasing mid-high level clouds mainly north of I-80 with a
small possibility of light rain showers north of Susanville-Gerlach.
Temperatures will be mild with highs approaching 70 degrees for
warmer valleys of western NV.

The most notable and glaring change in the medium range forecast
shows up on Thursday, as the 12z ECMWF drops a vigorous low directly
over the Sierra and western NV (a few hundred miles farther west
compared to the 00z ECMWF). The GFS and ensembles are not as
aggressive as the ECMWF and the variance of scenarios does reduce
the overall forecast confidence, but the trend now appears to favor
a better chance of showers and cooler temps on Thursday (a reversal
from previous model runs). Therefore we adjusted the forecast
accordingly (but not to the extent of the 12Z ECMWF). Decent
instability is likely with this system, so we added a slight chance
of thunder for Thursday afternoon-evening over northwest and west
central NV. If the more aggressive ECMWF scenario verifies, the risk
for thunder would extend farther west across the region.

By Friday, the precip chances should be over (except for possibly a
few showers early in the day east of US-95), but continued north to
northeast flow around the back side of the departing low will make
for a brisk day with daytime highs a few degrees below average.
Strong north to northeast ridge level winds could develop early
Friday and continue into Saturday morning, depending on how quickly
the low departs from the Great Basin. Otherwise for Saturday, there
is better agreement among the guidance sources that an upper level
ridge will build inland over CA-NV, leading to decreasing winds and
a decent warm-up. Highs are likely to rebound to above average,
mainly in the 60s for lower elevations and 50s near the Sierra. MJD



VFR conditions with generally light winds will prevail at the main
terminals through Sunday morning. Some obscurations of higher peaks
are possible thru this evening and again Sunday morning due to areas
of stratocumulus. Increasing cloud cover should limit FZFG formation
at KTRK tonight-early Sunday, although we can`t completely rule out
the possibility of patchy short duration fog if the thicker clouds
hold off until after daybreak.

For Sunday night-Monday, another storm system will move quickly
through the region with periods of snow producing IFR conditions at
times  in the Sierra and northeast California. In the lower valleys
a brief period of rain or a rain/snow mix is possible by early
Monday morning. Winds will also increase Sunday afternoon-evening
with gusts up to 30 kt in lower elevations and up to 65 kt over
Sierra ridges, leading to areas of turbulence and mountain wave
activity. MJD


.REV Watches/Warnings/Advisories...


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