The large upper level ridge parked over eastern Alaska and western Canada is going to provide one last gasp of arctic chill this week. Then the weather pattern will become more tranquil and seasonable.
However, this air mass, arriving from high latitudes, will ensure a wintry blast to parts of the northern tier and the Inter-mountain West.
The chilling effects start today across Montana. After three days with afternoon highs in the 60’s, Great Falls will see its temperatures only rise into the mid 50’s before the passage of the arctic front. Tomorrow, with snow, blowing snow and gusty northeast winds, the temperature will be hard-pressed to stay in the 20’s and could even fall to the teens before sunset. Wind chills will likely fall to near zero.
In fact, winter weather warnings and advisories cover much of Montana early this Sunday morning, Oct. 27, 2013.
By late Monday afternoon, much of the Inter-mountain West will be experiencing a wide array of winter weather hazards, including heavy snow, blowing snow, high winds and even some mixed frozen precipitation (Fig. 1). Ski resorts will be thrilled with the snowy weather to help build or build upon a skiable base. Motorists will need to be aware of rapidly changing road conditions (either from place to place or even at a single location).
As the cold air builds eastward, it will reinforce the chill already present. Temperatures will continue some five to ten degrees below average from the northern Plains into the Northeast. Gale warnings are posted for parts of Lake Superior; otherwise, places near Great Lakes shorelines will have to deal with small craft advisories.
This chill will not reach as far into the Deep South as previous arctic blasts earlier this month have. And, once this system kicks out into the Great Lakes by Halloween Eve, more moderate Pacific air masses will entre the picture. Hence, November promises to begin with weather conditions much closer to average across much of the Nation.
© 2013 H. Michael Mogil