Area Forecast Discussion
Issued by NWS Reno, NV

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071
FXUS65 KREV 192046
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
146 PM PDT Tue Sep 19 2017

.SYNOPSIS...

A strong cold front will bring windy conditions Wednesday, with
well below average temperatures continuing through the weekend.
Freezing or near freezing temperatures in some lower elevation
valleys are possible starting Friday night. Light showers, with a
dusting of snow in higher elevations, are possible at times from
Wednesday through Friday.

&&

.SHORT TERM...

The forecast thinking remains on track, with low pressure near the
Queen Charlotte Islands to drop into the Pacific Northwest tomorrow
and push a cold front through northeast California and western
Nevada tomorrow night. Deep forcing for precipitation is simulated
to remain over central and eastern Nevada Wednesday night and
Thursday as the cold front enhances the thermal packing along a
lead boundary there. Still, a quick shot of isolated to scattered
light rain and high Sierra snow showers is expected with either the
lead thermal gradient (Wednesday afternoon/early evening) or the
cold front and main upper low (Wednesday night/early Thursday).
Snow levels should remain high enough that travel impacts are not
anticipated even over the highest Sierra passes.

Winds Wednesday look relatively unimpressive with gusts mostly in
the 30-40 mph range (45-50 mph in wind-prone areas) Wednesday
afternoon and early evening. With moisture simulated to increase
quickly Wednesday afternoon downslope potential looks low and/or
short-lived (Mono County) at best.

Thursday and Friday, very chilly air (but not unheard of) for
this time of year settles into the region as a large-scale upper
trough remains overhead. Lower valley highs are expected to top
out in the upper 50s to mid 60s, with 30s to low 40s above 8000
feet. Isolated to scattered showers are possible Thursday and
Thursday night before tapering off Friday as the upper trough
begins to edge off into eastern NV.

.LONG TERM...Saturday through Tuesday...

Drier northerly flow is expected over the weekend, with increasing
ridging for early next week. The main concern will be the potential
for freezing or near freezing lower valley temperatures for Saturday
and Sunday mornings. The uncertainty will be in residual higher
cloud cover which could modify temperatures slightly, however,
lows are still expected to fall well down into the 30s for lower
valleys outside of highly urbanized ("concrete jungle") locations.
Be prepared to take precautions if you have vegetation sensitive
to frost or light freezes.

Temperatures should modify back towards average early next week
which should ease the threat for lower valley frosts or freezes.
-Snyder

&&

.AVIATION...

Winds increase significantly again Wednesday along and ahead of a
cold front. Widespread surface gusts 30-35 kts are expected, with
gusts to 40-45 kts in wind-prone locations. Ridge gusts in excess
of 70 kt are expected. This will lead to increased turbulence and
localized pockets of low level wind shear.

The winds should decrease Wednesday evening into Thursday morning,
but an upper low settles over the region that will result in
unsettled weather through at least Thursday night. High elevation
snow showers and increased moisture/clouds could bring areas of
higher terrain obscuration starting Wednesday evening. -Snyder

&&

.FIRE WEATHER...

Wind gusts Wednesday afternoon and evening along and ahead of the
next cold front are expected to reach 30-40 mph, locally 45-50
mph in wind-prone areas. Precipitation will be limited in eastern
CA and western NV, although there is a better chance of light
showers along the front as it is more dynamic than the front that
passed through Monday.

While winds are going to be gusty Wednesday, humidity values are
expected remain higher than they did Monday. Most areas are
expected to remain above 25% all day with a rapid increase in the
evening as colder air invades the region. Lower humidities could
briefly occur south of Highway 50 in the Basin where they could
bottom out between 15-20% late Wednesday morning into early
afternoon; however, the time for near critical conditions should
only last 2-4 hours. While wind is often the main factor for fire
spread in the fine Basin fuels, the threat should taper off in the
evening as humidities rise and winds decrease behind the front.

With all this in mind, the chance for critical/near conditions
for more than a few hours is low so we will refrain from issuing
any watches or warnings and just headline strong gusty winds in
the planning forecast. -Snyder/??

&&

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

     Lake Wind Advisory from noon to 9 PM PDT Wednesday for Lake
     Tahoe in NVZ002.

CA...Lake Wind Advisory from noon to 9 PM PDT Wednesday for Lake
     Tahoe in CAZ072.

&&

$$

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



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