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fxus65 krev 150945 
afdrev

Area forecast discussion
National Weather Service Reno Nevada
245 am PDT sun Sep 15 2019

Synopsis...

Strong winds and a dry air mass will be in place through Monday
ahead of a powerful cold front. Road and air travel, lake
recreation, and critical fire weather impacts are expected.
Showers and cooler temperatures can be expected Monday, with some
very light snow in the mountains. Another storm system is possible
for the middle of the week with drier conditions and near average
temperatures by the end of the week.

&&

Short term...

Strong winds and dry conditions are still the main concern today
as a powerful cold front approaches the region. This will lead
to long duration, high-end critical fire weather conditions
through Monday until the cold front and rainfall move through the
region. See the fire weather discussion below for more information.

Sustained southwesterly winds of 15-30 mph with gusts up to 40-45
mph are expected for most locations, however wind prone areas
particularly along the Highway 395/I-580 corridor could see gusts
of 50-60 mph due to downslope enhancement off the mountains. The
strongest winds today are expected in the late afternoon to early
evening timeframe as the strongest 700mb winds aloft arrive across
the Tahoe basin and Sierra front.

In addition to the high fire weather concerns, the strong and gusty
winds will make for hazardous boating conditions (lake wind
advisories in effect), reduced visibility in areas of blowing dust,
possible travel restrictions for high profile vehicles, and aviation
turbulence/wind shear (see aviation discussion for more details).

As the cold front nears the I-80 corridor early Monday afternoon,
the strongest winds will shift south of US-50, but still along
Highway 395 mainly from the Carson Valley through Mono County. Gusts
in these areas could still reach 50 mph.

Precipitation with the cold front will be concentrated mainly across
the northern Sierra and far western Nevada Monday morning and early
afternoon. Rain totals along the northern Sierra and far northeast
California generally look to be in the 0.30"-0.60" range with a
few tenths possible for far western Nevada and a few hundredths
farther east across the western Nevada basin and range. A few
thunderstorms are also possible with the front, which may
contribute to brief intensification of precipitation rates. Light
snow accumulations will also be possible mainly above 8,500' but
not looking much more than an inch or two particularly with
snowfall occurring during daytime heating.

The cold front will provide much cooler temperatures on Monday
with high temperatures falling 15-25 degrees from sunday's highs.
Expecting highs largely in the upper 60s to low 70s across
western Nevada valleys and upper 50s for Sierra valleys. Overnight
lows will bottom out for the week Tuesday morning. Frost and
freezes are concerns for lower elevation valleys outside of
population centers with freezes almost certain for Sierra valleys.
Wednesday morning will also start fairly cold, but temps will be
moderated by clouds advancing ahead of our next trough. Fuentes



Long term...Wednesday through next weekend

Higher confidence this morning on the next low dropping in Wednesday
night into Thursday. Precip chances were increased area wide with
some showers possible as far south as Mammoth and Hawthorne.
Temperatures were decreased Wed-Fri with the ensembles in better
agreement with a deeper trough as well. Little change was made to
the forecast next weekend.

With the next low dropping in, it will be breezy Wednesday ahead of
the cold front, but peak gusts will only be 25-35 mph. We expect
showers behind the front beginning Wednesday afternoon north of I-80
and Thursday morning for Mono and Mineral. Much cooler with
showers Thursday and highs only in the 50s and 60s as the low moves
through.

The low likely pulls away Friday with drying conditions, but it will
still be cool. Ensembles are in better agreement this morning with
any subsequent short waves just brushing by the area to the north.
This would likely result in temps near average with dry conditions,
consistent with the going forecast. X

&&

Aviation...

VFR conditions today, but the big concern remains the long duration
wind event. Winds already gusting on ridges up to 40 kts and these
will continue to increase. Peak gusts of 25-40 kts are expected at
area terminals by late this morning. Ridge gusts will increase to 60-
75 kts by this afternoon. Winds will continue into Monday, but may
weaken at times for the Sierra front terminals (krno/kcxp/kmev). Mtn
wave turbulence will occur along with low level wind shear. The low level wind shear is likely to be
strongest 06-18z Monday with the strongest ridge winds, along with
the occasional lighter gusts in the valleys.

Precip is expected behind the front Monday afternoon and evening.
MVFR ceilings/visible in the Sierra with rain showers from ktvl northward. Western
Nevada terminals will see localized MVFR ceilings in the showers. Shsn will
occur above about 8000 feet, but this will not affect any terminals
except on approach.

Another cold storm is on tap for Wednesday into Thursday. Winds on
Wed will not be as strong as this current system peaking near 30
kts, but more showers are likely Wed night into Thursday. X

&&

Fire weather...

..strong, long duration red flag event Sunday into Monday...

..Particularly dangerous situation (pds) in the foothills along and
west of Highway 395 and Interstate 580...

The strong wind event is just beginning at this time with ridge
winds gusting to 50 mph and poor recovery. Some localized valley
areas are already seeing red flag conditions such as Stead which has
been gusting 35-40 mph with 9% relative humidity the past hour.

Winds aloft continue to increase today and peak tonight. Very dry
air will mix down today with single digit and teens relative humidity. Wind gusts
of 35-45 mph are likely in most areas today through Monday. For wind
prone areas near Highway 395, some downslope enhancement is expected
which will result in gusts up to 60 mph. For this reason, the periods
wording was included for these areas. Any fires that start in this
area would be susceptible to extreme growth in a short period of
time.

The winds will continue into Monday. While relative humidity will increase tonight,
it won't be that much and would still be capable of supporting fire
growth with the strong winds. On Monday, relative humidity will increase with
showers expected behind the front. For northern areas, the showers
and moisture increase will begin sometime Monday morning, but
not until the mid to late afternoon for Mono and Mineral counties.
Wetting rains are expected north of I-80 with some areas in the
northern Sierra seeing 1/2 inch or more. X

&&

Rev watches/warnings/advisories...
Nevada...red flag warning from 8 am this morning to 2 PM PDT Monday
nvz450.

Red flag warning from 8 am this morning to 11 am PDT Monday
nvz458.

Lake Wind Advisory from 11 am this morning to 8 PM PDT Monday
for Lake Tahoe in nvz002.

Red flag warning from 2 PM this afternoon to 6 PM PDT Monday
nvz453-459.

Lake Wind Advisory from 11 am this morning to 8 PM PDT this
evening for Pyramid Lake in nvz004.

Lake Wind Advisory from 9 am to 8 PM PDT Monday for Pyramid Lake
in nvz004.

California...red flag warning from 8 am this morning to 2 PM PDT Monday
caz271-278.

Red flag warning from 8 am this morning to 11 am PDT Monday
caz270.

Red flag warning from 2 PM this afternoon to 6 PM PDT Monday
caz273.

Lake Wind Advisory from 11 am this morning to 8 PM PDT Monday
for Lake Tahoe in caz072.

Red flag warning from 11 am this morning to 11 am PDT Monday
caz272.

&&

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