473
FXUS65 KREV 200858
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
158 AM PDT Sun Jul 20 2025

.KEY MESSAGES...

* Isolated showers and thunderstorms are possible this afternoon
  in eastern Mono and Mineral counties.

* Stronger winds for Monday will bring elevated to critical fire
  weather concerns, and may impact travel and recreation.

* Hazy skies continue in far northeast California and northwest
  Nevada from wildfire smoke. Typical July heat continues today,
  then some cooling arrives from Monday onward.

&&

.DISCUSSION...

The nearly consistent weather pattern for the past few days will
hang on for today, although hints of a change will come later in
the day as a trough of low pressure in southwest Canada starts to
drop southward to the Pacific Northwest. SW-W winds will edge
upward a bit this afternoon in response to increased SW flow
across the Sierra, leading to drier air pushing farther east
across areas which received thunderstorms yesterday. Today, the
potential for PM showers and isolated thunder is largely limited
to the eastern portions of Mono and Mineral County, with less
coverage and lightning activity compared to yesterday.

Smoke and haze from fires in northern CA will continue to affect
parts of northeast CA-northwest NV through this morning. Then as
winds kick up this afternoon, the next round of smoke and haze
from today`s fire activity looks to shift farther north to the
Surprise Valley and far northwest NV, bringing slight reductions
in air quality. Patchy blowing dust could be carried from the
sinks and deserts of northwest NV as winds increase later today,
along with choppy lake conditions on a day with higher recreation
activity, so we`ll be issuing a Lake Wind Advisory.

For Monday, the trough makes its closest approach to CA-NV with
wind speeds peaking as it swings through the region during the
day. 700 mb flow increases to 25-30 kt with surface wind gusts
around 35 mph across much of western NV and Sierra ridge gusts
around 50 mph. These conditions will bring increased fire weather
concerns (see the Fire Weather section below for more details),
along with impacts to lake recreation, with Lake Wind Advisories
also in place for most of Monday. Areas of blowing dust from the
deserts and sinks of northwest-west central NV also become more
likely Monday afternoon.

Along with the winds, we`ll see about 5-10 degrees of cooling
across most of the region Monday. Similar temperatures (about 4-8
degrees below late July averages) are expected to prevail for the
bulk of the upcoming week with highs mainly in the upper 80s-lower
90s for lower elevations and 70s for Sierra communities. Nights
will be even a touch chilly for late July, with lows mainly in the
50s for most lower elevations and upper 30s-40s near the Sierra.
Precipitation chances look to be low across the region with the
exception of some slight chances (~15%) for light showers/thunder
Monday near the OR border. Then for Wednesday and Thursday,
isolated PM shower and thunderstorm chances may return from the
eastern Sierra northward across far western and northwest
NV/northeast CA, resulting from a weak closed low lingering near
or off the northern CA coast producing areas of instability.
Confidence is lower on this storm potential, due to some spread in
the medium range ensemble guidance on the location and extent of
this low. A few scenarios keep this low around even longer which
would lead to a daily risk of isolated PM showers/thunder into
next weekend. MJD

&&

.AVIATION...

VFR conditions prevail for the next few days with the risk for
isolated thunder around KMMH decreasing to around 10% this
afternoon, and no storms expected for the other main terminals.

Winds will edge upward this afternoon mainly from 21-04Z with
gusts 25-30 kt at the main terminals, except 20-25 kt for
KTVL/KTRK. Winds increase further Monday with Sierra ridge gusts
up to 45 kt for much of the day and afternoon gusts 30-35 kt at
the main terminals. This will produce periods of mountain wave
turbulence and occasional LLWS from Monday morning through
evening. MJD

&&

.FIRE WEATHER...

Elevated to critical fire weather conditions are expected across
the region today and especially Monday as increasing westerly
winds and low humidity prevail. Portions of the Sierra Front and
Northern Washoe County have a 40% probability of reaching critical
fire weather thresholds for 1-3 hours this afternoon-early
evening.

The risk becomes more widespread on Monday, as an approaching
upper level trough strengthens winds aloft tonight through
Monday evening. Fire weather watches remain in effect for surface
wind gusts near 35 mph, coupled with minimum afternoon humidity
levels of 1015% in the Northern Sierra Front (Zone 420) as well
as the Basin and Range areas (Zones 423 and 429) for a span of 3-6
hours. These regions will also have poor humidity recovery tonight
with maximums only from 25-35%, adding to the already dry
conditions after last weekend`s heat and only sparse rainfall so
far this month.

In Northern Washoe County, fire weather concerns remain elevated
on Monday but are expected to stay below critical levels due to
increases in humidity as a surface front moves through overnight
into early Monday. At this time, the eastern Sierra and northeast
CA have not reported critical fuel conditions. Be sure to avoid
activities that could spark a fire, and stay updated with the
latest fire weather warnings and forecasts. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 11 AM to 11 PM PDT Monday NVZ001>004.

     Fire Weather Watch from Monday afternoon through Monday evening
     NVZ420.

     Lake Wind Advisory from 2 PM this afternoon to 11 PM PDT this
     evening NVZ002-004.

     Fire Weather Watch from Monday afternoon through Monday evening
     NVZ423-429.

CA...Lake Wind Advisory from 11 AM to 11 PM PDT Monday CAZ071-072.

     Lake Wind Advisory from 2 PM this afternoon to 11 PM PDT this
     evening CAZ072.

&&

$$