Juneau residents awoke Thursday to a rime of frost glazing windshields and roads. On their iPhones, there was a forecast of something else to come: snow.
Rick Fritsch, lead forecaster for the National Weather Service in Juneau, has some thoughts on that.
“Don’t believe the snow,” he said in an interview Thursday morning.
Weather forecasts by iPhone typically come from the commercial firm Accuweather or the Weather Channel. Both of those companies typically rely on number-based models for deciding which places are likely to get rain and which places will be cold enough for snow.
“Those models, which are tuned for the Lower 48 … (do) not work up here,” Fritsch said.
The Weather Service operates a network of measurement and forecasting stations across the country, including in Juneau. Weather Service forecasters live in Juneau and know the local environment. Accuweather and the Weather Channel don’t have local forecasters, and while they can buy data from the Weather Service, their forecasts aren’t as accurate in places with unique conditions.
“That’s the problem with a lot of those iPhones,” Fritsch said.
It’s also why on Thursday, while iPhones showed snowflakes for Juneau’s forecast next week, the Weather Service didn’t. The only snow in its extended forecast for northern Southeast is in the mountains north of Haines and Skagway. Two inches of heavy, wet snow was expected in White Pass by Friday morning.
On average, Juneau’s first snowfall doesn’t come until Nov. 4, as measured at the airport, where the Weather Service has recorded precipitation since 1936. The city’s first inch of snow comes Nov. 10.
The city’s earliest snowfall was Oct. 2, 2000, and its latest first snowfall was Dec. 14, 2002. Last year, six-tenths of an inch of snow fell on Oct. 15. It was the first time since 1940 that Juneau had snow before Fairbanks or Anchorage.
As for frost, the Weather Service doesn’t track first frosts, Fritsch said. Those depend on both temperature and the amount of moisture in the air. This year, the capital city’s low temperature hit the freezing point on Oct. 2, but the air was so dry that no frost developed.
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