For the past week, a persistent upper level wind flow pattern has carried a series of storms from the western Pacific into the Alaska region. These have produced abnormally warmer and wetter than average weather in Alaska. Several locations have set daily and monthly records for precipitation and/or temperature. These conditions have kept the ground from freezing in some places and contributed to a significant snowmelt in others. In Alaska, frozen ground and/or snow cover takes the place of a roadway system in many places and is needed for ensuring transportation viability.
Most recently, the remnants of Typhoon Wipha moved into the Bering Strait, adding more warmth and moisture to the mix. Strong winds (gale to hurricane force) accompanied the storm’s arrival in the western Aleutians late last week (Fig. 1).
And a series of intense low-pressure systems, including what will eventually become the remnants of Super Typhoon Francisco, will be affecting the Aleutian Island chain and southern Alaska during the next few weeks.
This surge in warmth will generate a large upper level ridge over eastern Alaska and western Canada. Then, much like what happens when a wave is created in a rope held by two people, the upward bulge is linked to a downward push downstream. Hence, look for an intensifying upper level trough, coupled with the advance of very cold air, into most of the central and eastern US from now (Oct. 20, 2013) until the end of the month. With cold air spilling southward across the still warm Great Lakes, the “lake effect” snow machine should start to kick in.
The cold air has already reached parts of the central US. For example, Minneapolis, MN has seen below average readings for the past three days. Oklahoma City, OK has averaged about 10 degrees below average for much of the past week.
As the workweek unfolds, Minneapolis is expected to see daytime highs not even reach the average daily temperature readings. The cold air mass will take a few days to reach places in the Mid-Atlantic and Northeast. Most of the Florida peninsula won’t feel its full effects, although drier air will likely reach as far south as the Florida Keys. Still, the cold air is coming to much of the US.
In between the wet and warm Alaska conditions and cold and mostly dry weather across the central and eastern U.S., most of the western US. will experience a warm and dry weather pattern.
© 2013 H. Michael Mogil