Tuesday, December 18, 2012

Major Winter Storm on the Way

Residents from the Colorado Rockies to the Great Lakes are bracing for a major winter storm Wednesday and Thursday, while the Pacific Northwest gets a breather between storms today.

Yesterday the large upper trough along the Pacific coast produced more wind, rain and snow in the Pacific Northwest. Winds gusted to more than 80 miles per hour along the coast, and there were blizzard conditions in the mountains where snowfall in the Washington and Oregon Cascades totaled from one to three feet.
CoCoRaHs snowfall map for Washington for December 18, 2012
Forecast surface map for 7:00 EST December 19
This large trough will continue to progress east tonight and tomorrow. By Wednesday morning a surface low associated with that trough will be organizing over Colorado. The surface low is expected to move to northern Oklahoma by Wednesday evening, to central Illinois by Thursday morning, and then to southwestern Michigan by Thursday evening. It will be rapidly intensifying during the day on Thursday and along with the snow will be high winds.

 In the mountains of northwest Colorado up to 20 inches of snow is expected, and to the east significant snowfall is expected from Nebraska to the upper Great Lakes. Another system moving in from the Pacific will being more heavy snow to the Pacific Northwest.

Probability of 4 or more inches of snow for the period from Wednesday evening
to Thursday evening (left), and from Thursday evening to Friday evening (right).
As you might expect, a variety of winter advisories, watches, and warnings are in effect from the Rockies to the Great Lakes.

Watch/warning map valid as of 4:45 pm EST December 18.
Orange is a Blizzard Warning. Pink is a Winter Storm Warning.
Blue area surrounding pink is a Winter Storm Watch.
This is a great time for CoCoRaHs observers in the Plains and Midwest to review snow measurement procedures. Check out the snow measurement videos on CoCoRaHS YouTube channel, and/or the "In Depth" Snow Measurement training slide show on the CoCoRaHS web site.

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