SLAMMING THE DOOR...
That whistling wind you heard overnight was the result of a cold front that slammed the door on Friday's mild air. Highs in all areas were in the 50s with a couple spots in far SE Iowa touching 60 degrees. At 3:15 Friday afternoon Shenandoah in SW Iowa was 63 while 200 miles away in far NW Iowa it was a mere 23 degrees with wind chills down around 7.
By 1:00am was doing its dirty work in my area when readings looked like this.
That's the powerful front that steamrolled the area overnight bringing the high winds and sharply colder temperatures. Saturday morning we start the day in the teens and with strong cold air advection continuing all day, highs will only respond upwards a few degrees. That keeps most of us in the range of 23-28 for highs. In the afternoon readings will be about 30 degrees colder than 24 hours earlier. Wind chills will be in the single digits and teens all day long, although winds will decrease significantly later in the day as the pressure gradient eases.
Saturday night winds are already returning to the south starting our next warm-up in this push pull pattern. By Sunday we are back around 40 with Monday seeing low to mid 40s, perhaps a 50 far south. Of course, by then winds have turned frisky again, first from the south, then the north as out next cold front zips on by. It's at this point, we finally settle into a pattern for several days where temperatures are less extreme and not far from normal. The national model blend shows highs Tuesday through Sunday (of next weekend) in the range of 34-38 degrees.
That get us out to December 11th and this is the time frame where things have the potential to get more interesting. All the teleconnections indicate the AO (Arctic Oscillation) and NAO (North Atlantic Oscillation) being strongly negative, which favors cold. Blocking is firmly established at northern latitudes and retrogressing west from Greenland towards Alaska. Cold air will be forced to undercut the block and should begin to dominate the pattern with widespread cold over the central and eastern U.S. The EURO control shows these temperature departures December 13th-18th.
The blocking should also lead to a storm track that's more favorable for storm systems to impact the central Midwest. With cold air in place, snow chances should increase as well. The means of the EURO, GFS, and Canadian ensembles are starting to come in snowier. Take a look at the snowfall output, most of which falls between the 10th and 18th of December.
The EURO ensemble mean
The GFS ensemble mean
The Canadian ensemble mean
There's a lot of details to work out but I think this December has a lot more winter in it than what we've experienced in recent years. More to come.
With that, I will leave you to enjoy what promises to be a cold Saturday. Have a fine weekend and roll weather...TS