textproduct: Reno

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.