961
FXUS65 KREV 202117
AFDREV

Area Forecast Discussion
National Weather Service Reno NV
217 PM PDT Mon Jul 20 2026

.KEY MESSAGES...

* Afternoon shower and thunderstorm chances each day through
  midweek, with a drier pattern more likely returning by late
  week.

* Abundant moisture and slower storm motions will introduce flash
  flooding potential from heavy rainfall as the main concern today
  and Tuesday.

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

&&

.DISCUSSION...

Today:

* Convection is developing near Lee Vining and Bridgeport within
  today`s favored corridor from Mono County north through the
  Walker, Smith, and Mason Valleys into Mineral and southern Lyon
  Counties. Showers and thunderstorms have a 30-50% chance south
  of I-80 and east of US-395, with peak coverage from noon-7 PM
  and activity possibly lasting through 11 PM. NBM 12-hour thunder
  probabilities range from 30-35% across Mono and Mineral Counties
  and 20-25% across southern Lyon County, decreasing to 10-20%
  around Tahoe, Carson City, and Reno. PWATs of 0.9-1.3 inches are
  around 160-200% of normal. Forecast soundings show midlevel RH
  of 85-95%, locally 1000-1200 J/kg of MUCAPE, freezing levels
  near 15-17 kft MSL, and warm-cloud depths around 1.5-2.5 km in
  the more humid profiles. This supports efficient warm-rain
  processes and locally intense rain rates. NBM areal-average QPF
  through Tuesday morning is generally only a few hundredths to a
  few tenths, but embedded convective maxima approach one inch.
  HREF/REFS members produce localized multi-inch totals,
  highlighting the difference between areal-average QPF and
  rainfall beneath an individual storm. Corfidi vectors of 15-20
  kt indicate greater storm translation than expected Tuesday,
  although terrain anchoring and redevelopment along intersecting
  outflows could still produce repeated heavy rain. Isolated
  outflow gusts of 50+ mph and small hail are secondary concerns.
  Showers may linger overnight, with around a 5-10% chance of
  lightning.

Tuesday & Wednesday:

* Moisture peaks Tuesday, with PWATs of 0.9-1.3 inches, or roughly
  200-250% of normal. The favored heavy rain corridor expands from
  Mono, Mineral, and southern Lyon counties northwest through the
  Carson Valley and eastern Tahoe slopes into the Virginia Range
  and Truckee Meadows. NBM 12-hour thunder probabilities increase
  to 40-50% across Mono, Mineral, and southern Lyon Counties,
  35-45% around Carson Valley, and 30-40% across Tahoe and Reno-
  Sparks. Breaks in the cloud cover and western NV valley highs
  well into the 90s should support roughly 500-1500 J/kg of
  MUCAPE. Forecast soundings also maintain deep midlevel moisture
  and freezing levels near 16 kft MSL. Corfidi propagation vectors
  weaken to 7-10 kt, increasing the potential for slow-moving
  clusters and repeated development over similar areas. Given the
  broader coverage, anomalous moisture, and slower propagation, a
  second Flood Watch has been issued from noon-11 PM Tuesday. This
  includes today`s watch area and expands north into the Tahoe
  Basin and Reno-Carson City-Minden corridor.

* Thunderstorms remain possible Wednesday, primarily south of
  I-80. NBM 12-hour thunder probabilities are around 20-25% near
  Reno, Carson City, and Tahoe and 30-35% near Bridgeport,
  Hawthorne, and Mammoth Lakes. Coverage will be lower than
  Tuesday, while faster storm motions should reduce the duration
  of heavy rainfall over any one location. Localized flooding
  remains possible where repeated rainfall occurs during the
  preceding two days. Convection diminishes Wednesday evening,
  with most areas dry by 12Z Thursday.

Thursday through Monday:

* Monsoonal moisture begins shifting east Thursday, with 12-hour
  thunder probabilities decreasing to around 5-15% across western
  Nevada and the eastern Sierra. Similar probabilities continue
  Friday through Monday, generally remaining below 10% north of
  I-80 and locally reaching 15-20% near southern Mono County over
  the weekend. Thus, an isolated storm cannot be ruled out near
  Mono County or the Nevada Basin and Range, but widespread
  convection is unlikely. Increasing afternoon west winds are
  possible Thursday and Friday as drier air arrives. Otherwise,
  warm and mainly dry conditions are favored through Monday, with
  western Nevada valley highs in the 90s and locally near 100
  degrees.

-Johnston

&&

.AVIATION...

* VFR will prevail outside convection through 22/18Z. Thunder
  probabilities today are around 30-35% near KMMH and 10-20% near
  the Tahoe and western Nevada terminals. Tuesday probabilities
  increase to 40-50% near KMMH and 30-40% near KTVL, KTRK, KCXP,
  and KRNO. Direct impacts could produce brief MVFR/IFR
  visibility, mountain obscuration, small hail, and erratic
  outflow gusts approaching 40 kt. Activity should diminish after
  06Z Wednesday.

* KRNO: West winds increase gusting to 25 kt from 23-04Z, then
  decrease from the northwest overnight. There is a 30% chance of
  -SHRA from 00-10Z, with VCSH from 04-10Z. Ceilings near 9 kft
  and VFR visibility are expected. The 12-hour probability of
  thunder increases to around 35% Tuesday afternoon and evening,
  with abrupt wind shifts and brief visibility reductions possible
  near storms.

-Johnston

&&

.HYDROLOGY...

* A Flood Watch remains in effect from 2-11 PM today for Mono
  County and Mineral/southern Lyon Counties. A second Flood Watch
  has been issued from noon-11 PM Tuesday for those areas plus the
  Tahoe Basin and Reno-Carson City-Minden corridor. WPC maintains
  a Marginal Risk (at least 5%) for excessive rainfall across
  southern portions of the region today, expanding north across
  western Nevada and the Tahoe Basin Tuesday. Today`s primary
  flash flood corridor extends from Mono County through the
  Walker, Smith, and Mason Valleys into Mineral and southern Lyon
  Counties. Tuesday`s corridor expands 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

&&

.REV Watches/Warnings/Advisories...
NV...Flood Watch from Tuesday afternoon through Tuesday evening
     NVZ001>003.

     Flood Watch until 11 PM PDT this evening NVZ001.

CA...Flood Watch from Tuesday afternoon through Tuesday evening
     CAZ072-073.

     Flood Watch until 11 PM PDT this evening CAZ073.

&&

$$