Severe Thunderstorm Warning 37, NWS Reno, NV

Area Forecast Discussion
National Weather Service Reno NV
129 PM PDT Thu Sep 25 2025

.KEY MESSAGES...

* Shower and thunderstorm chances continue this afternoon, mainly
  south of I-80, along with a risk for heavy rain that could lead
  to flash flooding in Mono, Mineral and southern Lyon counties.

* Another low pressure system early next week brings potential for
  cooler temperatures, increased precipitation chances, and gusty
  winds.

&&

.DISCUSSION...

Periods of showers and isolated thunderstorms are occurring
across western NV, the Sierra and NE California early this
afternoon as seen on radar. This showery activity is expected to
continue through the afternoon and end around sunset. More
thunderstorms are expected this afternoon, especially in areas
south of US-50. The main hazard with any storm south of US-50 will
be periods of heavy rain that could lead to flash flooding and/or
mudslides near steep-terrain in Mono, Mineral and southern Lyon
county. As we move into the afternoon hours the southerly flow
slows down as the upper low moves south resulting in slower moving
storms that could anchor themselves near mountains. Furthermore,
we have plenty of moisture with PWs between 0.6-0.8 inches and
instability reaching 500-700 J/kg of MUCAPE. All those
environmental conditions should support the development of storms
this afternoon from the Eastern Sierra towards southern Lyon and
Mineral as seen in the latest HREF run.

Activity appears to end mostly after sunset as the low continues
its southward path. This will lead to a break in precipitation
from this system starting this evening through Saturday morning
for Mono/Mineral, and through Saturday evening for the rest of the
region. Don't be surprised if there are a few stray showers down
in southern Mono tomorrow. Otherwise, the rest of the area will be
dry. Anyway, there is a 10-20% chance isolated showers and storms
affecting the Mono/Mineral area on Saturday afternoon.

Active weather continues on Sunday as a broad upper level trough
descends from the Gulf of Alaska. This system will pull back the
low that is affecting us today resulting in low chances of
precipitation, 10-25% for areas north of US-50, and 25-50% for
areas south of US-50. The extra moisture leads to more clouds
which leads to slightly cooler temps on Sunday too.

This broad upper level trough will affect us through the first
half of the week bringing cooler temperatures, gusty winds, and more
chances for showers and thunderstorms. Its associated cold front
should pass through the region on Monday night or Tuesday morning.
Thus the coolest day of the next week will be Tuesday with
afternoon highs possibly in the low 60s to low 70s western NV and
NE CA, and 50s to low 60s for Sierra communities. Winds increase
early next week with a 30-60% chance of observing gusts exceeding
35 mph. Plus we are looking at more widespread shower activity
areawide. There is still some model disagreement, and the
aforementioned details could change but the trend is looking at
cooler, wetter and windier conditions than this week.

-HC

&&

.AVIATION...

Showers and isolated thunderstorms continue this afternoon over
Sierra terminals mainly south of Lake Tahoe. KMMH may see MVFR
conditions due to a 60-80% chance of storms through 03Z. Chances
for showers will be around 10-30% for KRNO/KTVL/KCXP/KMEV this
afternoon. Main hazards will be heavy rain, small hail,
occasional lightning, and terrain obscuration. The heavy rain
hazard is more likely for areas south of US-50, not so much for
areas to the north. Chances will taper as the sun sets this
evening, with drier conditions tomorrow.

-HRICH/HC

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch until 8 PM PDT this evening NVZ001.

CA...Flood Watch until 8 PM PDT this evening CAZ073.

&&

Preliminary Local Storm Report
National Weather Service Reno NV
202 PM PDT Thu Sep 25 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0201 PM     Hail             1 SW Toms Place         37.55N 118.71W
09/25/2025  M0.25 Inch       Mono               CA   Trained Spotter

            Also received about 0.26 inches of rain with
            the storm.

&&

HC