Update - February 17, 2015 - Unsettled Weather

In the post I did on Friday, click here, I discussed that due to lack of snow cover across much of the northern plains that the Arctic airmass might be modified a bit.  The cold air that arrived Saturday, spreading northeast to southwest, was certainly modified.  While record setting cold has gripped the upper midwest and northeast, here in the high plains it has turned colder but definitely not brutal.

This mornings snow and ice analysis showed more of the country covered - compared to last Friday. 

You can see last Friday's map by clicking here.

One reason the center of the cold, this time, has not impacted the high plains is due in part because of the orientation and location of the upper ridge.  I've marked that location on the satellite image below.  It is farther east this time (as opposed to the November and early January versions).

Another reason, in part, that the Arctic air has not spread back against the Rocky Mountain front range is that the Arctic Oscillation has been strongly positive.  That was unforeseen this go round.

But will both the ridge and AO stay in this configuration?  Not entirely.

The two X's on the satellite image off the Pacific Northwest coast represent two systems in the upper atmosphere that will be rounding the top of the ridge and then will most likely amplify as they turn south.  This should initially bring a brief "warm up" to the area late in the week.  Depending on the amount of amplification and the eventual track, there should be active weather developing in the Rockies by Saturday, and possibly spreading into the plains.  In addition, the amplification will allow the Arctic airmass to move south but also west.  I'll update later in the week, but be prepared for unsettled and increasingly colder weather by the weekend, especially for Colorado.

On the Arctic Oscillation  - if the index dives into the negative during the next 7 to 10 days, then the last week of February would be brutally cold across the area.  I'm not confiident of the severity, but it does look like the balance of the month will be mostly below normal, as far as temperatures.

One of the long range computer forecasting models does show a trend to stay colder than normal right through much of March.  I do think there will be a warmup, but March typically can become pretty variable in terms of weather systems.

 
I would agree that the month on average may end up below normal, but I bet there will be some pretty mild periods too, most likely during the mid part of the month.   This will have to be watched in case it gets "out of control" and gets the winter wheat to break out of dormancy.  Look out for the threat of a March blizzard the last 10 days of the month followed by a significant cold period the first week of April!