779
FXUS65 KREV 211038
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
338 AM PDT Tue Jul 21 2026

.KEY MESSAGES...

* Afternoon shower and thunderstorm chances are forecast through
  Wednesday, with a drier pattern more likely returning by late
  week.

* Abundant moisture and slower storm motions will allow flash
  flooding potential from heavy rainfall to be the main concern
  today.

* Typical July warmth, breezy afternoons and drier conditions may
  produce elevated fire weather conditions at times later this week
  and into the weekend.

&&

.DISCUSSION...

Last night`s showers have carried into this morning according to the
most recent radar returns. The latest run of the HREF shows
showers becoming more isolated with chances lowering to around
~15% in NE CA, far NW NV, and near the Sierra crest in Alpine and
Mono Counties through the late morning. While other areas of the
CWA may see a break from precipitation chances this morning, the
CWA remains underneath the influence of a high pressure ridge and
having a southerly flow aloft bringing in more monsoonal moisture
today. The latest model PW values continue to max out at around
0.9-1.3 inches today though some models are showing areas of up to
around 1.5 inches in the NV Basin and Range. With CAMs showing
another round of showers and thunderstorms today, these well-above
normal values mean that heavy rainfall is possible once again.
Storm motions expect to be slow as well so there is a Flash Flood
threat within the region, especially if there are training
thunderstorms. Refer to the current Flood Watch product and the
Hydrology section for more details. With the flash flooding
threat, conditions can become extremely dangerous quickly. If you
encounter a flooded roadway, remember: "Turn around, don`t drown!"

Forecast guidance is showing cloud cover lessening going through the
this morning in portions of S. Mono County as well as over the NV
Basin and Range, which will allow for more diurnal heating in
these areas and increasing instability for convection. Models
reflect this with CAPE values between 500-1500 J/kg today, so
stronger thunderstorms that do develop today could also produce
strong outflow wind gusts of 50+ mph and small hail. The NBM
probabilities for thunder across the region today are around
20-60% with the higher end chances in the aforementioned areas. As
for precipitation chances today, areas along and south of I-80
have around 50-90% chance with portions to the north having
around a 20-50% chance. Aside from the morning precipitation, the
HREF has showers and thunderstorms initiating in the Eastern
Sierra by around 11-12 PM PDT with coverage spreading northward
going through the afternoon and evening. While chances taper down
overnight, portions of W NV north of US-50 see a 10-20% chance of
lingering showers going into Wednesday morning. Please stay
weather aware today and have a way to receive the latest weather
alerts.

For Wednesday, CAMs are showing around a 15-40% chance for
afternoon showers and thunderstorms with the higher end chances
in Mono County and adjacent portions of Mineral County. Other
areas highlighted for these precipitation chances include Eastern
Pershing and Churchill Counties, along the OR border, and the
Reno-Sparks area as well. However, forecast guidance is showing
that bulk of the monsoonal moisture will shift eastward with high
pressure moving into OK/TX. Model PW values come down to around
0.5-0.8 inches on Wednesday, which brings the flooding threat down
a bit (though there some heavy rainfall may still be possible
with thunderstorms). Will continue to monitor these flooding
chances especially with rainfall occurring in the previous two
days.

For the rest of the week and going into the weekend, afternoon
precipitation chances gradually diminish though portions of Mono
County and the NV Basin and Range may see 10-20% chances through
Saturday. Forecast winds will increase on Thursday and going
through the weekend with afternoon gusts up to around 25-35 mph
possible. Daytime high temperatures for the W NV valleys will be
in the 90s with some portions reaching the triple digits for the
latter half of the week. Sierra communities have highs generally
in the 80s. As conditions dry out with these temperatures, the
increased winds may allow for elevated fire weather concerns
especially in NE CA and NW NV. -078

&&

.AVIATION...

VFR conditions are expected at all area TAF sites through around
21/18Z with low shower chances (10-20%) in the Sierra and near
the OR border. After 21/18Z, widespread showers and thunderstorms
are expected in the region. NBM thunder probabilities increase to
around 40-50% for all TAF sites. Direct impacts from thunderstorms
today could produce brief MVFR/IFR visibility from heavy
rainfall, mountain obscuration, small hail, and erratic outflow
gusts approaching 40 kt. Precipitation chances should diminish
after 22/06Z though lingering showers are possible in W NV. Lesser
chances (20-40%) for showers and thunderstorms are seen on
Wednesday in the Sierra and Sierra Front with drier conditions
forecast through the latter half of the week. -078

&&

.HYDROLOGY...

* A Flood Watch remains in effect today from noon-11 PM for the
  Tahoe Basin and Reno-Carson City-Minden corridor as well as
  Mono, Mineral, and southern Lyon Counties. The WPC has
  introduced a Slight Risk (at least 15%) for excessive rainfall
  covering Mono and Mineral Counties as well as southern Lyon
  County in their latest outlook for today. Remaining areas along
  and south of US-50 are in a Marginal Risk (at least 5%) for
  excessive rainfall for today as well. Today`s primary flash
  flood corridor extends from Mono County through the Walker,
  Smith, and Mason Valleys into Mineral and southern Lyon Counties
  as well as north into the Carson Valley, eastern Tahoe slopes,
  Virginia Range, and Reno-Sparks area. Individual storm tracks
  remain uncertain, but repeated development could produce flash
  flooding near steep terrain, burn scars, normally dry channels,
  and urban areas. Clear drains where possible to limit urban
  ponding. Area rivers and streams could see rapid rises and
  increased sediment loads with localized heavy rain, but no river
  flooding is expected.

-Bardsley/Johnston/078

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch from noon PDT today through this evening NVZ001>003.

CA...Flood Watch from noon PDT today through this evening CAZ072-073.

&&

$$