textproduct: Reno

KEY MESSAGES

* Strong south to southwest winds develop over the Sierra tonight and spread into valleys across the region Friday.

* Heavy Sierra snow and western Nevada valley rain peak Friday afternoon and evening, then taper by Saturday morning.

* After a dry break this weekend, a colder storm brings more mountain snow and light valley rain Sunday night into Tuesday.

DISCUSSION

Storm 1 - Friday through Saturday morning

* Friday's cold front will bring a several hours of heavy, wet snow to the Sierra. The heaviest snow is expected from 2 to 8 PM around Tahoe and from 3 to 10 PM in Mono County. Rates of 1 to 2 inches per hour will sharply reduce visibility in the heavier bands, with brief rates near 3 inches per hour along the crest. Snow showers linger behind the cold front into early Saturday.

* Winds pick up ahead of the snow. Southwest winds will build waves on Lake Tahoe tonight. Friday's south to southwest gusts reach 45 to 55 mph in many exposed valleys and up to 70 mph along wind prone areas such as Lundy Canyon and Lee Vining along US-395 in Mono County. Blowing dust may briefly reduce visibility in the Basin and Range. The Wind Advisory runs from 7 AM to 7 PM Friday in Surprise Valley and northern Washoe County and from 10 AM to 10 PM in the other valley advisory areas.

* Around Tahoe, expect about a foot of snow above 7,000 feet, with up to 20 inches on the crest west of the lake. Rain changes to snow at lake level Friday evening as snow levels fall toward 5,500 feet. The chance of at least 8 inches through Saturday morning is about 55 to 70% at Donner and Echo Summits, 70 to 90% on parts of the crest, and generally below 10% at lake level.

* In Mono County, snow levels start near 8,000 feet Friday afternoon, close to the elevations of June Lake and Mammoth Lakes. They fall as the heaviest band arrives, reaching roughly 7,000 feet by 8 PM and near 6,000 feet late Friday evening. Expect 2 to 4 inches near June Lake village and 3 to 6 inches in Mammoth Lakes, with higher totals along the Sierra crest. The chance of at least 6 inches is about 20% in June Lake village and 60% in Mammoth Lakes. An earlier switch to snow would give either town more time under the heavy band. The high Sierra closer to the crest stays cold enough for 1 to 2 feet.

* Along US-395, Deadman and Conway summits both rise above 8,000 feet, but less moisture reaches the highway east of the crest. Around 1 to 3 inches is most likely at the summits, with a better chance of locally higher amounts at Deadman. Lower stretches near Bridgeport, Lee Vining, and Mammoth Yosemite Airport see more rain before the changeover, with little accumulation to around an inch.

* Western Nevada sees most of its rain Friday afternoon and evening. Expect around half an inch in the wetter foothills, a tenth to a third of an inch from Reno-Sparks through the Carson Valley, and less than a tenth across much of the Basin and Range. As the front passes Friday evening, snow levels fall through 6,500 feet and approach 5,500 feet by late evening. The higher southwest Reno foothills near Galena have the best overlap of cold air and lingering showers, with a 25 to 40% chance of at least an inch. Upper Geiger Grade could turn to snow around 5 to 7 PM, followed by Virginia City as showers taper. A dusting is possible in both places, but an inch is unlikely (less than 5%). The Reno-Sparks valley floor will most likely see rain through this event (less than 5% chance of a trace of snow).

Weekend break - Saturday afternoon through Sunday afternoon

* Once Saturday morning's snow showers end, dry weather is expected across the Sierra and western Nevada through much of Sunday.

Storm 2 - Sunday night through Tuesday morning

* The second storm is colder, with weaker winds carrying moisture up the Sierra. The steadiest snow is likely late Sunday night into Monday morning around Tahoe, then Monday afternoon and evening in Mono County, with showers lingering into early Tuesday.

* Several Sierra passes could see 3 to 8 inches, with amounts approaching a foot along parts of the crest. Over the duration of the storm, probabilities of more than 6 inches of snow range from 45 to 60% at several Tahoe-area passes to around 75% along portions of the higher Sierra crest. Most western Nevada valleys are forecast to receive a few hundredths to around a tenth of an inch of rain, with locally higher amounts along the Sierra front. Snow levels may reach 5,000 to 6,000 feet as showers taper Tuesday morning.

Break and Another Storm - Mid-to-late next week

* A few Sierra snow showers may linger Tuesday afternoon, especially in Mono County. Most of western Nevada should be dry, with a break in precipitation across much of the region Tuesday night. A colder storm approaching from the Gulf of Alaska could bring another round of Sierra snow by Wednesday afternoon, continuing into Thursday. Snow levels could fall into the western Nevada foothills and possibly reach some valley floors. Whether snow accumulates in the valleys will depend on how much moisture remains when the colder air arrives.

-Johnston

AVIATION

* KRNO: VFR this afternoon and tonight. Light east to southeast winds turn southerly this evening. LLWS is possible as early as 05Z Friday and likely by 10Z. Southerly surface gusts increase to 20-30 kt Friday morning, then peak at 35-40 kt around 21-23Z. South to southwest winds of 45-50 kt at 2,000 ft AGL favor another period of LLWS and turbulence around 21-00Z. Rain is most likely late Friday afternoon, with visibility briefly near 5 SM and ceilings around 3,500 ft AGL near 00Z Saturday. By 03Z Saturday, winds turn west to west-northwest near 10 kt with gusts around 20 kt.

* Regionally: VFR prevails through Friday morning. LLWS develops this evening at the Sierra terminals and overnight at KCXP and KMEV. South to southwest winds reach 45-55 kt at 1,500-2,000 ft AGL at KTRK, KTVL and KMMH Friday afternoon, with mountain wave turbulence over and east of the crest. Peak surface gusts range from 25-35 kt at KCXP and KMEV to around 40 kt at KTVL and KMMH.

* 24-72 hour outlook: At KTRK and KTVL, ceilings lower to MVFR Friday afternoon. As rain changes to snow around 00-03Z Saturday, periods of IFR/LIFR are likely, with visibility locally 1/2 SM or less and widespread mountain obscuration. Snow reaches KMMH Friday evening, with MVFR likely and brief IFR possible. KRNO, KCXP and KMEV may see brief MVFR in rain Friday evening. VFR returns to most terminals Saturday afternoon and prevails through much of Sunday. Another storm approaches the region Sunday night into Monday.

-Johnston

REV Watches/Warnings/Advisories

NV...Wind Advisory from 7 AM to 7 PM PST Friday NVZ005.

High Wind Watch from Friday morning through Friday evening NVZ005.

Wind Advisory from 10 AM to 10 PM PST Friday NVZ001-003-004.

Lake Wind Advisory from 10 PM this evening to 10 AM PST Friday NVZ002.

Winter Storm Warning from 10 AM Friday to 10 AM PST Saturday NVZ002.

CA...Wind Advisory from 7 AM to 7 PM PST Friday CAZ070.

High Wind Watch from Friday morning through Friday evening CAZ070.

Wind Advisory from 10 AM to 10 PM PST Friday CAZ071.

Lake Wind Advisory from 10 PM this evening to 10 AM PST Friday CAZ072.

Winter Storm Warning from 10 AM Friday to 10 AM PST Saturday CAZ072.

Winter Storm Warning from 1 PM Friday to 10 AM PST Saturday CAZ073.