Biggest imapct: Wyoming-South Dakota; but cold & wet in Colorado too

12:45 PM, Friday, May 8, 2015

A big wet storm system to our west will keep it cloudy and rainy through tonight, with snow above 8000 feet. As the storm moves from the Four Corners Saturday morning to northeastern Colorado Sunday morning, we may see several phases of the storm play out. The strongest westward moving moisture flow may shift north into Wyoming during the day Saturday. As the storm moves into northeastern Colorado Saturday night and Sunday morning, moist northerly flow in eastern Colorado may reinvigorate the precipitation as the snow levels fall. Near freezing temperatures are likely even in many low elevation areas Sunday and Monday mornings.

Here is a regional breakdown:

Northeastern Colorado & the Front Range, including Denver, Boulder, Fort Collins and Nederland:

Through early Saturday: Clouds and rain. There may be some locally heavier showers or a thunderstorm that trigger brief minor flooding. Snow levels may lower again to 8000 feet, but the accumulating snow will be mainly above 9000 feet.

During the day Saturday: an area of slightly drier air (a dry slot) should move into southeastern Colorado and there is a chance it may move into northeastern Colorado too for a period. I think you should be prepared for a cloudy, rainy day even though I think the odds slightly favor a lull period. If the sun manages to poke through briefly, that may trigger thunderstorms during the afternoon, possibly strong thunderstorms on the far eastern plains.

Saturday night and Sunday: northerly flow is likely to bring moisture back from the north along with colder temperatures. Rain will likely change to snow down to 7000 feet Saturday night, and possible all the way down to the lower elevations Sunday morning as the precipitation becomes more intermittent.  Snow totals of 1-6 inches should be expected from 6000-800 feet, with 6-12 inches above 8000, and maybe some local areas of 2 feet in the mountains of Larimer and northern Boulder County. I cannot yet rule out some accumulation in the Denver-Boulder-Fort Collins corridor. I will update tomorrow.

Wyoming:

Cloudy and rainy through Saturday (snow above 8000 feet), with snow levels dropping to the lower elevation areas Saturday night. Total snow accumulation through Sunday is likely to be 10-20 inches in the higher ranges of eastern Wyoming and the Black Hills of South Dakota. Even the Cheyenne area is likely to see 6-10 inches.

Southeastern Colorado, including Colorado Springs:

Rainy with some thunderstorms into tonight. Slightly drier air coming up the east side of the storm circulation is likely to result in a lull Saturday. But thunderstorms may develop in the afternoon, and some may be severe on the far eastern plains. A surge of colder, moist air out of the north Sunday will likely result in mostly cloudy conditions and some showery rain and snow.

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