OGDEN -- Last week was perfect late-summer bicycling weather, and this week the National Weather Service has "be sure to put a winter storm survival kit in your car" on its telephone hold message.
It's a very abrupt change, and they aren't kidding.
A winter storm front was supposed to pass over Top of Utah around midnight Wednesday night, which means there should be snow as far down the mountains as 6,500 feet today and Friday. More significantly, National Weather Service hydrologist Brian McInerney said there will be as much as 18 inches of snow on the mountains' upper heights.
Temperatures will barely budge out of the 40s, so wear your woollies. A winter storm warning has been issued and will be in effect through 3 p.m. Friday.
"Its going to bring colder air, 20 degrees lower than normal, and we're going to see snow accumulations down to 6,500 feet," McInerney said, which puts it more than halfway down Mount Ogden.
"But the real accumulation is above 8,000 feet" -- between 10 and 18 inches.
"We had a big high-pressure ridge over the Western United States for about six weeks," he said. That giant pillow of heavy air kept storms away.
Now it's gone. A giant well of low pressure off the California coast is spinning counter-clockwise, picking up moisture off the ocean "and bringing it up into Utah in a southwesterly flow."
Benches and valley areas will see as much as half an inch of rain, he said, while drivers in the mountains and upper valleys can expect snow-packed roads.
"So if you're going to be driving in the upper mountain areas, you want to be on your game, because these storms catch people off guard."
McInerney said this is a good way to start the water year, which begins Oct. 1.
Separately, the Utah Snow Survey by the National Resource Conservation Service issued its Oct. 1 water year report saying that weather conditions are setting up similar to last year's, when record snowfall caused heavy runoffs.
The report says La Nina conditions, a cooling of equatorial waters off of South America, are back.
"When La Nina conditions prevail, Northern Utah tends to have above-normal snowpacks and Southern Utah tends to have below-normal snowpacks," the report says. "We have only to refer to last year to see that these are tendencies only and that the unexpected can and will happen where southern Utah had a huge year bucking the normal tendencies."
Specifically, Utah got heavy snow in December, "when the so-called Pineapple Express formed and hit Utah with huge snowpack accumulations. This condition may or may not occur this year."
The Climate Prediction Center of the National Oceanic and Atmospheric Administration says a region stretching across Washington, Idaho, Montana and stretching down to Top of Utah will see above-average precipitation from December through February.