The Jet Stream has a lot to do with the current weather - it's dipping quite low, bringing warm weather to the east and cooler weather to the west.
Record breaking warmth across the United States in March 2012
It is technically winter, and the United States is experiencing a weather pattern typically seen in early summer. Unseasonably warm temperatures have developed east of the Rocky Mountains and have extended north into Canada.
Synoptically, or looking at the big picture, the weather pattern resembles a late May and early June pattern. More than 2,000 high temperature records have been tied or broken since March 1, 2012, and more are expected to be broken for the next couple of days, because the weather pattern is very slow to budge or move. What is causing this heat, and will this be a sign of a brutally hot summer?
For the month of February, we saw a lot of extremes across the globe. Earth likes to balance things out, so in a way, it makes sense that Europe and Asia experienced such extreme cold temperatures while the United States saw above average temperatures. In Europe and Asia, nearly 650 people died because of the extremely cold temperatures.
So much snow fell that these areas saw the third largest February snow cover extent since record keeping began. Australia also experienced a very cool summer and was ranked the 8th coolest minimum February. The last time Australia had such cool temperatures was back in 1990.
The image below shows the temperature anomalies for February 2012. The red dots show temperatures above average in that particular region. The blue dots show temperatures below average. As you can see, the North Pole and North America saw warmer temperatures while Europe, Asia, northwest Africa and Australia saw cooler temperatures.
Now, take a look at the record highs that have been set across the United States for the month of March so far. This includes dates from March 1, 2012, through March 15, 2012. Of temperatures recorded, 2,052 records were either tied or broken so far for the month of March. This number is expected to grow as the warm temperatures continue across the majority of the United States.
Temperatures have soared into the 70?s and 80?s Fahrenheit across Illinois, Indiana, Michigan and Wisconsin, and spreading as far north as North Dakota, Minnesota, and into Canada.
The main reason for these warm temperatures is based on the jet stream across the United States. A large trough has been in place across the western United States.
Troughs bring lower pressures and stormy weather across the affected regions. The western United States has been cooler and wetter the past few weeks, and for a good bit of this winter. Meanwhile, a large ridge has been built east of the Rocky Mountains. Ridges act as areas of high pressure that provide sinking air.
Warm air from the south has been spilling northward to provide record-breaking temperatures across the United States. The jet stream is responsible for this digging and lifting of these troughs and ridges. Due to the position of the jet, and the blocking features that are taking place, the warm spells are continuing into the weekend.
http://earthsky.org/earth/record-breaking-warmth-across-the-united-states-in-march-2012