A moderate chance of heavy snow has been added to the Sierra Nevada forecast for the weekend of Nov. 14 to 15. The National Weather Service office in Reno said in its afternoon forecast discussion on Nov. 6 that the Climate Prediction Center now puts that risk at 40% to 60%. It is the first sizable snow signal for the range since the Halloween-weekend storm closed two high passes.
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The window has tightened since early in the week. Coverage on Nov. 5 described the risk as running from Nov. 12 to 15 and tied it to a pattern change around Veterans Day on Wednesday, Nov. 11. Products issued on Nov. 6 center the best snow chances on Saturday and Sunday, Nov. 14 and 15, with a lower tier of risk lingering through Nov. 17 across several western ranges.
The Reno forecast discussion and its 40% to 60% call
In its discussion issued at 1:39 p.m. PST on Nov. 6, NWS Reno said a wetter and windier pattern remains on track to arrive late next week and carry into the weekend, while adding that the change is “not without its uncertainties.” The Reno office expects a stronger Pacific system to arrive over the Nov. 14 and 15 weekend with mountain snow, valley rain and wind, and it described the model agreement as fairly steady from one model run to the next. The office wrote that the Climate Prediction Center had added a moderate risk of heavy snow along the Sierra, quoting the 40% to 60% band, and flagged potential impacts to recreation and to air and ground travel.
The Climate Prediction Center’s hazards outlook, issued at 3 p.m. EST on Nov. 6 and signed by forecaster Thomas Collow, covers Nov. 14 to 20. It carries a moderate risk of high-elevation heavy snow for the Klamath and Sierra Nevada mountains on Nov. 14 and 15, plus a slight risk for the Cascades, Klamath and Sierra Nevada through Nov. 17. The outlook publishes risk categories rather than percentages, so the 40% to 60% figure is the Reno office’s reading of what a moderate category means. The same product lists a moderate wind risk for coastal Washington, Oregon and much of California on the same two days.
A window that slid two days later
Autoblog’s Adam Lynton reported on Nov. 5 that NWS Reno was calling for “a significant pattern change” around Veterans Day and that Climate Prediction Center guidance showed a 40% to 60% risk of heavy snow from Nov. 12 to 15. An atmospheric river tool in that report showed substantial moisture heading toward the region in the second half of the following week, and the office advised planning for wetter, cooler and windier weather. Model solutions, the article said, still diverged on details. By Nov. 6 the snow risk had settled on the weekend instead.
The Weather Prediction Center’s separate days 3 to 7 hazards page was issued on Nov. 5 and is valid for Nov. 8 to 12, so it stops short of the weekend in question. Its regional snow and rain areas appear only on a map graphic, not in text.
Chain controls and closures from the Halloween-weekend storm
Travelers have already seen what a modest Sierra storm does to the mountain highways. Active NorCal reported on Nov. 2 that snow began above 7,000 feet on Saturday, Oct. 31, after the National Weather Service in Sacramento called for up to 10 inches above 7,000 feet and as much as 18 inches on the tallest summits. The highest peaks picked up close to 2 feet by Sunday, Nov. 1. Chain requirements were in place on Interstate 80 over Donner Summit by nightfall Saturday, along with Highway 50 over Echo Summit and Highway 88 over Carson Pass, and Caltrans fully closed Sonora Pass on Highway 108 and Monitor Pass on Highway 89.
The rules behind those signs come from Caltrans. Under its R-1 level, most vehicles must carry chains, though passenger vehicles and light trucks under 6,000 pounds with snow tires on at least two drive wheels are exempt from fitting them. R-2 requires chains or traction devices on all vehicles except four-wheel and all-wheel drive models with snow-tread tires on all four wheels, and R-3 allows no exceptions. Speed is limited to 25 or 30 mph wherever chains are required, and the agency’s highway information line is 800-427-7623.
What stays unsettled before Nov. 14
Nothing in the Nov. 6 products gives a snowfall total for the Nov. 14 and 15 weekend, and the Reno discussion itself leans on probabilities rather than amounts. Its forecasters also noted that ensembles suggest more storms are possible during the week of Nov. 16, with lower confidence than the weekend signal. The next Climate Prediction Center hazards update will show whether the moderate snow risk for the Sierra holds, shrinks or picks up a higher category as the Pacific trough off the West Coast comes into clearer focus.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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