A major adjustment is taking place in the storm track/jet stream over a large portion of the U.S. and northeastern Pacific Ocean. The latest storm to move from the Pacific is affecting the southwestern states Wednesday night, bringing very strong and damaging winds to some sections of California.
Western Wyoming is now dominated by a cold northerly flow of drier air from Canada. As high pressure builds north into the Gulf of Alaska, this will put Star Valley under an extended period of possibly more than a week of reinforcing surges of cold air from Canada. With the storms tracking across western Canada and then southeastward…most of the snow will occur east of the Continental Divide.
This first chart shows the forecasted abnormally high pressure centered over the Gulf Of Alaska. The red contours in the chart are areas of higher than normally 500 mb heights, with blue contours indicating areas of below normal 500 mb heights.
|500 mb Anomalies Sat 12/3/11|
The models suggest that this pattern will persist as shown on the following chart displaying the same fields as the one above except for Wednesday of next week.
|500 mb Anomalies Wed 12/7/11|
This pattern will be characterized by only brief periods of clouds and light snow as disturbances pass through Star Valley. Much of the time for the next week will see only limited amounts of cloud cover allowing for nighttime temperatures to drop below zero, and afternoons remaining well below freezing.
Fortunately there is not a pool of Arctic air yet available in Canada, so even though the jet stream pattern will be favorable, a bitter cold air mass from the north is not expected at least into early next week. If the pattern persists, then the possibility of an arctic air mass invading Wyoming will increase.
Nevertheless conditions will be favorable for colder valley locations dipping to 10 below zero or lower Friday morning under clear skies.