323
FXUS65 KREV 222120
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
220 PM PDT Fri Aug 22 2025

.KEY MESSAGES...

* Areas of Major HeatRisk in lower elevations will peak today and
  shift to northeast CA and northwest-west central NV Saturday.

* Monsoonal moisture brings shower and thunderstorm chances mainly
  to areas south of US-50 this afternoon and evening.

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

&&

.DISCUSSION...

A brief period of late summer heat will give way to a prolonged
cooler and wetter pattern with advancing monsoon moisture. The
first round today will be more limited in storm coverage, but this
will increase from south to north through this weekend. By early
next week, an upper low off the west coast will likely also come
into play to draw in Pacific moisture and increased forcing as
well. Get ready for at least a few days of active weather!

Storm Chances:

* This afternoon-evening: Initial cell formation has just begun
  for Mono-southern Mineral/Lyon counties, as projected by the
  latest high resolution guidance. Storms will increase and
  develop farther north through the remainder of the afternoon
  across the eastern Sierra and western NV, mainly south of US-50.
  We also can`t rule out a couple of stray cells farther north
  around Reno-Carson City and the eastern Tahoe basin, with
  chances around 10%. There could be some fire weather concerns
  with lightning and stronger outflow gusts spreading into west
  central NV (more details in the Fire Weather section) into this
  evening, but with deeper moisture quickly advancing and
  potential for redevelopment of cells over some areas, heavy
  rainfall will become an increasing concern. This round of storms
  should wind down after 8-9 pm, although a few showers may
  linger overnight in Mono-Mineral counties.

* This Weekend: Storm coverage increases from south to north on
  Saturday, with the greatest chances (40-60%) across the eastern
  Sierra and western NV south of US-50. Between the US-50 and I-80
  corridors the shower/storm chances generally range from 30-45%,
  with lesser chances (10-30%) northward to the OR border. By
  Sunday, most areas have 40-70% shower/storm chances, except
  lower in Lassen County west of US-395. Main threats will be the
  typical small hail, gusty outflow winds, heavy rain, frequent
  lightning, but also with the risk of flash flooding especially
  for steep terrain, burn scars and urban areas. A potential
  limitation to t-storms is the extent of cloud cover. Due to the
  notably high moisture content (PW values rising to 0.9"-1.2" by
  Sunday), leftover upper level clouds from the previous day`s
  convection could stick around into the following day, which
  would cut into the amount of surface heating and instability in
  the afternoon.

* Next Week: Daily chances for showers and mainly afternoon
  t-storms continue each afternoon with highest confidence on
  Monday-Tuesday. The added forcing provided by the low off the
  west coast could shift higher chances of storms farther north
  into Tahoe and northeast CA/northwest NV, with solid precip
  chances continuing for the remainder of the region. Wednesday
  and Thursday are more of a wild card as the deeper moisture may
  start to decline, although some forcing for storms appears to
  remain in play, depending on the eventual track of the upper
  low. A more pronounced drying trend may finally take shape by
  next Friday through the Labor Day weekend, although isolated
  shower chances can`t be fully ruled out.

Temperatures and Winds:

* Temps peak today and Saturday in the upper 90s to around 100
  degrees in the lower elevations included in the ongoing Heat
  Advisory, while Sierra valleys warm up to the upper 80s-near 90.
  Overnight lows will remain on the warm side, only dipping to the
  mid 60s-lower 70s for the next couple of nights. While areas
  near and south of I-80 will start to see a dip in temperatures
  Saturday, a more notable cooling will arrive Sunday and continue
  through next week with highs settling into the mid 80s-near 90
  for lower elevations and mid 70s-near 80 for Sierra valleys. In
  areas where thicker cloud cover or rain persists into the
  afternoon, highs would end up 5-10 degrees cooler. While general
  winds look to be rather light for the upcoming week, outflow
  gusts associated with t-storms could surpass 40 mph, with
  stronger cells capable of 50-60 mph gusts. As we get to the
  Labor Day weekend, periods of increased winds may return,
  although confidence is relatively low this far in advance. MJD

&&

.AVIATION...

Density altitude concerns due to heat will affect western NV
terminals each afternoon through Saturday. Showers and
thunderstorms along with mountain obscurations are expected this
afternoon 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...

Increasing moisture will bring isolated-scattered thunderstorm
chances this afternoon-early evening to the eastern Sierra and
parts of western NV, mainly south of US-50. While precipitable
water values will increase relatively quickly to between 0.80-1"
and create 10-20% chance of wetting rain, the initial 1-2 hours
of storms could be accompanied by dry lightning strikes and gusty
outflow winds of 40+ mph. 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 until 9 AM PDT Sunday NVZ004-005.

     Heat Advisory until 9 AM PDT Saturday NVZ001-003.

CA...Heat Advisory until 9 AM PDT Sunday CAZ071.

&&

$$