923
FXUS65 KREV 120925
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
225 AM PDT Wed Aug 12 2026

.KEY MESSAGES...

* Thunderstorms with heavy rain, hail, and strong outflow winds
  will expand northward today and Thursday. This will increase the
  threat of flash flooding and new lightning fires.

* Cooler than average temperatures arrive Thursday and continue
  through the weekend.

* Thunderstorm chances decrease Friday with mainly dry conditions
  expected through the weekend.

&&

.DISCUSSION...

The combined effects of a low pressure trough off the CA coast and
a high pressure ridge near the Four Corners region will increase
moisture into the Sierra and western NV the next couple of days.
The added forcing provided by this low will also bring increased
coverage of showers and thunderstorms, expanding northward to the
Reno area and closer to the Bug and Stallion fires this afternoon.
Across the rest of western NV, the northward extent of the storm
threat reaches the I-80 corridor through this evening. Slower
moving storms with heavy rain capable of producing flash flooding
and increased lightning will be the primary threats, but stronger
storms could produce outflow gusts to 40 mph.

For late tonight through Thursday morning, much of the latest
guidance supports showers and embedded thunderstorms forming
across parts of far western and west central NV. This activity
then could extend into northwest NV, the Tahoe basin and far
northeast CA around daybreak and continue through late Thursday
morning, bringing an increased threat of lightning with limited
rainfall, as these areas are expected to be on the fringes of the
deeper moisture.

Then for Thursday afternoon-evening, the trough off the CA coast
ejects northward with stronger forcing allowing for a quicker
development of stronger storms near or just after midday. Mixed
layer CAPE values increase to 500-1000 J/kg in areas where cloud
cover from the morning showers/storms thins out. This greater
instability would support a few severe storms producing wind
gusts of 60+ mph and hail to near 1" diameter (or accumulations of
smaller hail). Storms look to form by early afternoon near the
US-395 corridor from northeast CA to Mono County, then spread to
the north and east across much of western NV through the remainder
of Thursday afternoon. Even though faster storm motions are
likely compared to today, heavy rain capable of producing flash
flooding remains a threat, especially in areas where cells
redevelop or persist for a longer time span.

For both days, some areas of western NV may see thicker cloud
cover form in the afternoon and limit the instability needed for
thunderstorms, but with abundant moisture in place, wetting
rainfall (at least 0.10") in the form of shower bands would
occur.

By Friday, thunderstorm activity diminishes and shifts to west
central NV as a drier southwest flow reaches the Sierra. Overall,
this weekend into early next week is favoring dry conditions,
with a less than 10% chance for showers near the Sierra and the
Oregon border. Temperatures hold below mid-August averages from
Friday through early next week, with highs mainly in the 80s for
lower elevations and 70s for Sierra communities. MJD

&&

.AVIATION...

Showers and thunderstorms may affect the western NV terminals
(15-20% chance) southward to KMMH (25-30% chance) this afternoon
mainly between 21-03Z. While the greater risk for persistent heavy
rain stays east of these terminals, a well placed storm could
bring rain sufficient for MVFR CIGS/VIS, outflow gusts of 30+ kt
and lightning affecting these terminal sites. For KTVL/KTRK, the
risk for storms affecting these sites is less than 10% through
this evening.

Overnight into Thursday morning, all main terminals have a 15-20%
chance for showers and isolated lightning from elevated convection
(instability aloft rather than surface-based).

Thursday afternoon could see stronger storms with more hazardous
aviation impacts near the western NV terminals and KMMH mainly
between 19-23Z, before the bulk of storm activity pushes to the
northeast.

Smoke from the Bug and Stallion fires north of RNO will lower
visibilities near the fire sites with potential impacts for KRTS
(Reno-Stead), but prevailing west winds should keep VFR
conditions for KRNO. The only exception is a small 5-10% chance of
a stronger t-storm outflow forming near these large fires and
pushing a larger area of smoke southward toward the Reno vicinity.
MJD

&&

.FIRE WEATHER...

Moisture continues to advance northward across the eastern Sierra
and western NV today with more storms producing wetting rainfall.
However, the northern edge of these storms including near the
I-80 corridor and the Bug and Stallion fire sites may be a mix of
dry and wet storm types, with a risk of new fire starts from
isolated lightning strikes outside the rain cores, along with
outflow wind gusts to near 40 mph.

Areas from the Tahoe basin northward to Lassen and northern
Washoe counties will be on the edge of the moisture increase,
with an increased risk of dry lightning strikes as soon as early
Thursday morning. By Thursday afternoon-early evening, a mix of
wet and dry storms with faster storm motions is anticipated. With
lower humidity hanging on longer and plenty of dried out
vegetation from the recent heat event, a Fire Weather Watch
remains in place through much of Thursday for these areas. MJD

&&

.REV Watches/Warnings/Advisories...
NV...Fire Weather Watch from late Wednesday night through Thursday
     evening NVZ458.

     Flood Watch from Wednesday afternoon through Thursday evening
     NVZ001-003.

CA...Fire Weather Watch from late Wednesday night through Thursday
     evening CAZ270>272-278.

     Flood Watch from Wednesday afternoon through Thursday evening
     CAZ073.

&&

$$