Flash Flood in California, August 27, 2025

Area Forecast Discussion
National Weather Service Reno NV
1217 PM PDT Wed Aug 27 2025

.KEY MESSAGES...

* Thunderstorms and an elevated risk of flash flooding are expected
  this afternoon, especially over urban areas and burn scars.

* A drying trend will reduce thunderstorm activity into the weekend,
  but areas of isolated storms remain possible into early next week.

* Temperatures remain cooler than normal into the weekend, but
  will warm-up through Sunday.

&&

.DISCUSSION...

A shortwave trough will be passing through today, leaving our CWA on
the edge of the left exit region of the upper level jet streak.
Because of this, another round of showers and t-storms are expected
this afternoon. Thursday, the trough moves further east and shifts
all of its forcing and instability over central/eastern NV. We may
see some chances for showers and storms over Mono/Mineral/E.
Churchill Thursday, though models are still struggling to come to a
consensus on location. Friday through this weekend look to be a bit
quieter. We'll have less available moisture and less instability to
fire off thunderstorms.

Diving in further on today's storms: Going through the CAMs, MUCAPE
today will be around 400-600 J/kg and DCAPE around 800-1000 J/kg.
That's enough DCAPE for storms to produce strong outflow boundaries
that could produce gusts up to 40+ mph. PWAT values are slightly
elevated around 0.75-0.85". Storm motions continue to be on the
slower side today, less than 10 kt, so flash flooding remains a risk
where stronger storms stall out, back build, or train. Especially
since we've had multiple rounds of heavy rain over the past few
days, the ground is primed for faster runoff. If you're out on a
lake today or over in the Black Rock Desert, please be cautious and
have a way to receive weather alerts! Shower and t-storm chances of
30-40% will continue today across the entire CWA, with storms
starting as early as 11 AM. Similar to yesterday, storms will start
along the Sierra and propagate east through the afternoon. Expect
small hail with occasional hail that's up to a quarter in size,
gusty outflow winds up to 45-50 mph, heavy rain with potential
flash flooding, and possible blowing dust over the playa. I will
note too that ensembles are hinting at the possibility of a trace
of snow this evening in southern Mono and the White Mountains as
showers are dissipating and surface temperatures cool off. While
still a very low probability (<10%), it's a non-zero chance.

As alluded to earlier, Friday onward we get into this drier pattern
and high pressure starts to work its way in. Ensembles are showing
the possibility of showers in the Sierra each afternoon through the
weekend, however most CAMs don't show anything in the way of precip,
yet. All the storms aside, for the rest of the week we're going to
warm up a little bit each day and temps will warm back up in lower
NV valleys to 90 by Saturday.

-Justin

&&

.AVIATION...

Widespread coverage of showers and thunderstorms are expected once
again this afternoon. Brief periods of IFR conditions are
possible due to heavy rain and sudden reductions to visibility.

The best chances for thunderstorms today will be around 60-70% at
KMMH and terminals in the Sierra and Sierra Front, including 40%
at 88NV in the Black Rock Desert. Timing of these storms will be
as early as 12-1 PM for KMMH, 2-5 PM for 88NV, and 12-1 PM for
all other terminals. Main threats today with these storms will be
heavy rain, small hail, frequent lightning, and outflow gusts up
to 35 kts. Storm activity is expected to wrap up after 8 PM.
Additionally, low clouds and fog may produce a period of IFR
conditions at KTRK overnight tonight, particularly 11Z - 16Z.

-Justin

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch until 10 PM PDT this evening NVZ001>003.

CA...Flood Watch until 10 PM PDT this evening CAZ071>073.

&&

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Service Notice</title>
  <link rel="stylesheet" href="index.css">
</head>
<body>
  <main class="wrap">
    <section class="card" role="status" aria-live="polite">
      <div class="status" id="status">Temporary Notice</div>
      <h1 id="headline">This service is currently unavailable.</h1>
      <p id="message1">
        The site you requested is temporarily down for maintenance or an unexpected outage.
      </p>
      <p id="message2">
        Please try again in a few minutes.
      </p>
      <p class="small" id="detail">
        If you are an administrator, restore upstream service and remove the redirect/fallback rule when normal operations resume.
      </p>
    </section>
  </main>
  <script src="index.js"></script>
</body>
</html>

Special Weather Statement
National Weather Service Reno NV
150 PM PDT Wed Aug 27 2025

NVZ002-003-272115-
Greater Lake Tahoe Area NV-Greater Reno-Carson City-Minden Area NV-
150 PM PDT Wed Aug 27 2025

...A STRONG THUNDERSTORM WILL IMPACT STOREY...SOUTH CENTRAL WASHOE...
DOUGLAS AND NORTHERN LYON COUNTIES AND CARSON CITY THROUGH 215 PM
PDT...

At 149 PM PDT, Doppler radar was tracking a strong thunderstorm near
Carson City Airport, or near Carson City, moving east at 15 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Carson City, Washoe City, Pleasant Valley, Carson City Airport, New
Washoe City, Indian Hills, Washoe Lake Campground, Us 395 At
Douglas-Carson City Co Line, Lakeview, Gold Hill, Davis Creek
Campground, Stewart, Us 50 At Carson City-Lyon Co Line, and Junction
U.S 50 And NV 341.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3909 11982 3936 11989 3939 11968 3909 11957
TIME...MOT...LOC 2049Z 261DEG 14KT 3924 11978

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

JC

Special Weather Statement
National Weather Service Reno NV
151 PM PDT Wed Aug 27 2025

CAZ071-272115-
Lassen-Eastern Plumas-Eastern Sierra Counties CA-
151 PM PDT Wed Aug 27 2025

...A STRONG THUNDERSTORM WILL IMPACT WEST CENTRAL LASSEN COUNTY
THROUGH 215 PM PDT...

At 151 PM PDT, Doppler radar was tracking a strong thunderstorm over
Eagle Lake, moving east at 15 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Eagle Lake and Spaulding.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4060 12104 4082 12107 4084 12059 4061 12059
TIME...MOT...LOC 2051Z 251DEG 11KT 4068 12073

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

JC

Special Weather Statement
National Weather Service Reno NV
205 PM PDT Wed Aug 27 2025

NVZ001-272130-
Mineral and Southern Lyon Counties NV-
205 PM PDT Wed Aug 27 2025

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN MINERAL AND
SOUTHERN LYON COUNTIES THROUGH 230 PM PDT...

At 205 PM PDT, Doppler radar was tracking a strong thunderstorm 12
miles southeast of Mason, or 25 miles east of Topaz Lake, moving east
at 15 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Junction Nv 339 And Nv 208 and Pine Grove.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 3868 11916 3885 11920 3889 11887 3871 11884
TIME...MOT...LOC 2105Z 269DEG 12KT 3879 11908

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH

JC