646
FXUS65 KREV 212035
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
135 PM PDT Thu Aug 21 2025

.KEY MESSAGES...

* Areas of Major HeatRisk in lower elevations will peak on Friday
  and continue Saturday for northeast CA and northwest NV.

* Monsoonal moisture brings shower and thunderstorm chances to
  areas south of Interstate 80 by Friday afternoon.

* Showers and thunderstorms become more widespread along with a
  cooling trend starting on Sunday through most of next week.

&&

.DISCUSSION...

Advancing cirrus clouds are the initial signal of increasing high
level moisture for today, although the lower levels will remain
dry through early Friday. An expanding ridge of high pressure
extending from the eastern Great Basin to the southern Rockies
will draw in more lower level moisture starting Friday afternoon,
with south flow aloft setting up across the Sierra and western
NV. Temperatures will also reach their peak levels on Friday, with
highs near or above 100 degrees in many lower elevations of
western NV and northeast CA. This will be followed by a warm night
as cloud cover thickens, with lows ranging from the mid 60s-lower
70s. Similar heat is projected for Saturday followed by another
warm night especially from Susanville-Lovelock northward, so we
will be extending the Heat Advisories through Sunday morning
across much of northeast CA, northwest and west central NV.
Elsewhere on Saturday, more extensive cloud cover will bring a
slight 2-5 decrease in afternoon highs.

The first round of showers and thunderstorms resulting from the
moisture return is projected to begin Friday afternoon, with the
most favored areas including Mono, Mineral and Lyon counties
(20-35% chances). Lesser chances (10-20% chances) spread north
and west across parts of west central NV, far western NV and
Alpine county, and may come near the Reno-Carson-Minden areas,
depending more on outflow interactions and surface convergence.
Initial storms will likely form near the mountains after 2 PM,
then spread into lower elevations through late afternoon/early
evening. While some elevated fire concerns are possible as these
storms develop (see the Fire Weather section below for more
details), short bursts of heavy rain, gusty outflow winds of 40+
mph and small hail are also potential hazards. A few light rain
showers may also develop overnight into Saturday morning mainly
south of I-80.

By Saturday afternoon, the monsoonal moisture plume continues its
northward trek, with shower/t-storm chances spreading across much
of western NV and also the Tahoe basin northward to eastern
Lassen County. Heavy rainfall and localized flash flooding will
start to become more of a concern mainly from I-80 southward.
Precipitable water values continue to climb to near 1.0" which
could produce areas of limited convection due to overdeveloping
cloud cover, but instability should be sufficient with CAPE
values of 300-800 J/kg, that any period of clear conditions would
quickly lead to the development of storms.

For Sunday through the middle of next week, the high pressure
recedes to the south central US, but deep moisture remains in
place with precipitable water near or above 1.0". Meanwhile, an
upper low setting up off the CA coast will provide additional
forcing to keep shower and thunderstorm chances (mainly 35-70%
with highest end of range south of US-50) going each day. Cloud
cover thickness may inhibit convection in some areas, but storms
that do form could be prolific rain-producers. Therefore the risk
for flash flooding especially around burn scars, steep terrain
and urban areas will be on the rise for a good chunk of next week.
Temperatures will cool off starting Sunday, with highs settling a
few degrees below average--mainly in the 80s for lower elevations
and 70s for from Tuesday onward. If areas of thick cloud cover
and/or shower activity persist during the afternoon hours, some
valley sites could even remain below 80 degrees for one or more
days next week. MJD

&&

.AVIATION...

VFR conditions persist through Friday morning with mainly light
winds. Density altitude concerns due to heat will affect western
NV terminals each afternoon through Saturday. Showers and
thunderstorms along with mountain obscurations return on Friday
mainly for the eastern Sierra with about 20-30% chance of
affecting KMMH, and 10% or less chances for the other main
terminals. T-storm chances and associated impacts (MVFR/IFR
conditions with bursts of heavier rain, lightning, small hail and
outflow gusts of 35+ mph) will increase to all terminals each
afternoon from Saturday through the middle of next week. MJD

&&

.FIRE WEATHER...

Dry conditions continue through Friday morning, with heat peaking
Friday afternoon. Increasing moisture will bring isolated-
scattered thunderstorm chances Friday afternoon to the eastern
Sierra and parts of western NV, mainly south of US-50. While
precipitable water values will increase relatively quickly to
between 0.75-1" and favor wetter storms, the initial 1-2 hours of
storms could be accompanied by dry lightning strikes and gusty
outflow winds. For Saturday afternoon, a similar potential for
isolated dry lightning strikes/gusty outflows shifts to areas
north of I-80 to near the OR border. Otherwise, the influx of
deeper monsoonal moisture/higher humidity with increasing chances
of moderate to heavy wetting rainfall should limit the potential
for new lightning fire starts south of I-80 on Saturday and in all
areas from Sunday onward. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Heat Advisory from noon Friday to 9 AM PDT Sunday NVZ004-005.

     Heat Advisory from noon Friday to 9 AM PDT Saturday NVZ001-003.

CA...Heat Advisory from noon Friday to 9 AM PDT Sunday CAZ071.

&&

$$