textproduct: Reno

KEY MESSAGES

* Persistent rain this afternoon and tonight may cause localized flooding in northeastern Lassen County, Surprise Valley, northern Washoe County and northwestern Pershing County, especially near burn scars.

* Showers and isolated thunderstorms may produce small hail, gusty outflows and brief downpours this afternoon and evening. Snow bursts above 8000 feet may make Mono County passes slick.

* Northeast to east wind Friday night into Saturday bring rough conditions on Lake Tahoe and low wind chills on exposed Sierra peaks. Dry weather and cold nights prevail this weekend.

DISCUSSION

Storm precipitation so far:

* 36-hour quantitative precipitation estimates ending 11 AM PDT shows 0.25-0.75 inch around Tahoe/Truckee, Alpine County, Carson Valley and Lovelock/Fallon, locally over 1 inch east of Fallon. Estimates are generally under 0.25 inch across eastern Plumas/Lassen counties, Surprise Valley and northern Washoe County; elsewhere, mostly 0.05-0.50 inch, including Sierra Valley, Reno-Sparks, and Lyon, Mineral and Mono counties. Snowfall reports reached 3-5 inches in the high terrain west of Mammoth Lakes.

This afternoon through Friday morning:

* Satellite shows the closed low lifting northeast across California, with rain bands from Tahoe/Reno to Lovelock and the Black Rock Desert. Cold air aloft supports 700-500-mb lapse rates near 6.5-7.5C/km. Residual boundary-layer moisture and any heating beneath cloud breaks favor weak instability and a 20% thunderstorm chance, with small hail, downpours and gusty outflows.

* Mono County snow levels lower from 8000 to around 7500 feet this evening. Convective snow bursts support keeping the Winter Weather Advisory above 8000 feet through 5 PM, with lighter accumulations thereafter.

* Upper-level divergence ahead of a 90-110 kt jet and convergence along the cold front/outflow boundaries will make rain more widespread and persistent this afternoon and tonight. Thunderstorm chances diminish this evening, but continued ascent through moist air sustains steadier, locally heavy rain.

* Additional precipitation through Friday morning: 0.5-1.5 inches across northeastern Lassen County, Surprise Valley, northern Washoe County and northwestern Pershing County, locally over 2 inches possible. Expect 0.10-0.40 inch across eastern Plumas/southwestern Lassen counties, Tahoe/Truckee, Alpine County, Lovelock/Fallon and Mineral County; a few hundredths to 0.25 inch around Reno-Carson City-Minden and in Lyon/Mono counties. Locally higher totals remain possible beneath heavier showers.

* A Flood Watch is in effect through 5 AM Friday for the heavier- rainfall corridor from northeastern Lassen County and Surprise Valley into northern Washoe and northwestern Pershing counties, including the Biscar and S1-Vya burn scars. Prolonged runoff threatens burn scars, rural roads and culverts.

Friday through Sunday:

* Cooler, drier air settles in Friday as post-frontal winds diminish. North-northwest winds will generally be 10-15 mph, with gusts to 30 mph mainly in the morning, locally 35 mph near Pyramid Lake, Fernley, Fallon and Lovelock. Winds remain light around Tahoe/Truckee during the day Friday, with northerly winds near 10 mph in Mono County by afternoon. Morning lows range from the 20s in Sierra valleys to the 30s across much of western Nevada. Highs reach the upper 40s/lower 50s in Sierra valleys and mid 50s/lower 60s in lower western Nevada valleys.

* Sierra crest winds turn northeast-east Friday night into Saturday, combining with cold temperatures to produce low wind chills on exposed high higher peaks. These winds will also reach lake level, producing rough waters on Lake Tahoe. A Lake Wind Advisory has been issued from 8 PM Friday to 8 AM Saturday PDT. Clearing and lighter winds in sheltered valleys favor Friday night lows in the teens/lower 20s in Sierra valleys and 20s to near 30 from Reno-Carson City through Lovelock/Fallon. Ridging keeps the weekend dry.

Monday through next Friday morning:

* An early-week shortwave may brush the Oregon border, while most of northeastern California, the eastern Sierra and western Nevada remain dry through next Friday morning, October 30. CPC favors above-normal precipitation October 29-November 4, but confidence remains low in precipitation arriving before Friday morning.

-Johnston

AVIATION

KRNO... Mainly VFR; 30% chance of TSRA through 23Z with brief MVFR visibility and gusts to 35 kt. West gusts to 20 kt 23-03Z, then north winds overnight. Showers return 07-15Z with ceilings near 3500 ft AGL.

Regional... SHRA/isolated TS through 00Z bring mountain obscuration, brief MVFR/IFR and outflow gusts to 35 kt. Wet ground/light winds favor KTRK IFR visibility after 07Z. For 12-15Z, 18Z LAMP gives a 40-55% chance of visibility below 1 SM if showers persist. KTVL trends MVFR after 09Z; MVFR ceilings may linger at both through late Friday morning. Weekend concerns: KTRK fog/freezing fog and Sierra crest turbulence Friday night/Saturday.

-Johnston

REV Watches/Warnings/Advisories

NV...Flood Watch through late tonight NVZ004-005.

Lake Wind Advisory from 8 PM Friday to 8 AM PDT Saturday NVZ002.

CA...Flood Watch through late tonight CAZ070-071.

Lake Wind Advisory from 8 PM Friday to 8 AM PDT Saturday CAZ072.

Winter Weather Advisory until 5 PM PDT this afternoon CAZ073.