Area Forecast Discussion
Issued by NWS Reno, NV

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FXUS65 KREV 201024
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
324 AM PDT Wed Sep 20 2017

.SYNOPSIS...

A strong cold front will bring windy conditions today, with well
below average temperatures continuing through the weekend.
Temperatures may drop to near freezing in some lower elevation
valleys starting Friday night. Light showers, with a dusting of
snow in higher elevations, are possible at times today through
Friday. Next week is likely to be dry with a slow warming trend.

&&

.SHORT TERM...

Low pressure near the US-Canada border will dig southward into the
Pacific Northwest today, driving a cold front through the region
late this afternoon through tonight. This low will remain over the
Great Basin through Friday. For today, gusty winds will be the
primary weather feature, followed by sharply colder conditions
and periods of light rain showers, with snow showers in higher
elevations, from tonight through Friday.

Winds today will produce choppy conditions on area lakes, but
only isolated sites are expected to reach advisory criteria. More
details on winds are included in the Fire Weather segment below.

As for precipitation, the best chances for showers today will be
north of Susanville-Gerlach. While rainfall amounts will generally
be light, areas near the Oregon border may receive more than 0.10
inch this afternoon. By tonight, the best shower chances move
south along the Sierra, and also east of US-95 in the Basin and
Range. Upper level jet support appears to line up better with low
level frontal forcing during the late night hours, which would
lead to a short period of steadier precip for western Mono County
and eastern portions of Churchill and Mineral counties. For the
majority of tonight, snow levels will remain rather high, limiting
any possible light snow accumulations in the Sierra to higher
peaks above 8500 feet near Tahoe/Alpine County and above 9500
feet in Mono County.

For Thursday, a secondary shortwave moving into the Sierra could
trigger bands of showers near and north of the Tahoe basin during
the day, and spreading into parts of western NV including the
Reno-Carson vicinity. Snow could mix in at times even down to
near 6000 feet, but accumulations are unlikely on road surfaces.
By Thursday night and Friday, shower coverage will become more
sparse as overall moisture decreases and forcing becomes weaker.

The coolest temperatures of the week are expected Thursday and
Friday. Highs in most lower elevations are only expected to reach
the upper 50s to lower 60s, with upper 40s-lower 50s for most
Sierra valleys and 30s to lower 40s above 8000 feet. Lows could
drop into the 30s as soon as Friday morning for some lower
elevations with some sites possibly dipping to near freezing if
if sufficient breaks in the cloud cover occur. The potential for
freezing temperatures will increase this weekend across more
valley areas as drier air spreads over the region with light winds
prevailing. MJD

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

Upper trough remains over much of the west Saturday with winds
transitioning from north to northeast. While the upper jet is
still draped across the region, the lower level winds begin to
subside, so surface wind speeds will be trending lighter. With
clearing skies and light winds, surface radiation will be
maximized overnight. The potential exists for freezing or near
freezing lower valley temperatures for Saturday and Sunday
mornings. For any home gardeners who still have sensitive
vegetation growing, check your local temperature forecast. If the
forecast low is 40 degrees or below, you run the risk of seeing
frost as surface temperatures can often be several degrees colder
than the official forecast lows at approximately 6 feet off the
ground.

A highly amplified ridge begins to expand across the eastern Pacific
over the weekend, but its progression into the west coast is slowed
by the exiting deep trough. Model runs the past few days have been
slower in warming temperatures in the long term, but have agreed on
keeping the forecast dry. Latest progs indicate ridging building
into the west Tuesday, possibly lasting through the end of next
week. This will bring dry conditions and warming temperatures,
potentially bringing highs back into the 80s for western Nevada
and 70s in the Sierra. -Dawn


&&

.AVIATION...

Increasing cloud cover can be expected along the Oregon border
with a few showers possible this morning. Showers will expand
southward through the afternoon hours ahead of this trough, which
will lead to lowered CIGs. The main impacts today will be
increased winds with widespread surface gusts reaching 30-40 kts
and 40+ kts in wind-prone areas. Ridge wind gusts in excess of 70
kts are likely. Expect widespread turbulence along and east of the
Sierra front with areas of localized low-level wind shear.

Winds should decrease this evening into Thursday morning. Attention
then turns to unsettled weather beneath the upper level trough. Rain
and higher elevation snow showers will begin to spread across the
area from northwest to southeast, with lowering CIGs and VIS at
times. -Johnston

&&

.FIRE WEATHER...

Compared to the recent wind event Monday, winds today may be a
bit higher across the region with peak gusts 35-45 mph, and some
gusts near 50 mph in wind prone areas. However, humidity values
are not expected to be as low, with most areas expected to remain
above 25% all day with a rapid increase in the evening as colder
air and moisture invades the region. Lower humidities between
15-20% could briefly occur south of Highway 50 in west central NV
through early this afternoon before the peak winds arrive. These
areas may see wind/humidity conditions approach critical values
for a short duration, but the overall threat is lower compared to
Monday. We will keep the gusty wind headline in the planning
forecast as a heads-up message, but fire weather-related warnings
are not planned since conditions will become much more
unfavorable for rapid fire spread this evening and overnight
behind the cold front. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from noon today to 9 PM PDT this evening for
     Pyramid Lake in NVZ004.

     Lake Wind Advisory from noon today to 9 PM PDT this evening for
     Lake Tahoe in NVZ002.

CA...Lake Wind Advisory from noon today to 9 PM PDT this evening for
     Lake Tahoe in CAZ072.

&&

$$

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



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