A mild winter across the United States

In general, the lower 48 in the United States has seen very mild temperatures during the 2011-2012 winter.

Besides the Pacific Northwest and Alaska, snowfall has been very limited across the country. As of today, (February 3) the areas hardest hit with cold and snow have been Alaska and a large portion of central and eastern Europe. A jet stream, which practically acts as a boundary of cold air to the north and warm air to the south, has been stagnant across the United States and Canadian border with very few dips. When the jet stream “dips”, it becomes a trough and typically brings colder and stormier weather. However, these dips in the jet stream have not been substantial or long term to provide a sustaining cold pattern like it did back in January of 2011. Will February promise colder weather? What does a mild winter mean for spring 2012?

Take a look at the snowfall depth this year compared to 2011 at the same time. On February 1, 2011, the United States had 52.2% of the country covered in snow. On February 1, 2012, the United States only had 19.2% of the country covered in snow. Huge difference in one year!

Snow depth on February 1, 2011. Image Credit: NOHRSC
Snow depth on February 1, 2012. Image Credit: NOHRSC

As mentioned before, La Nina, the North Atlantic Oscillation (NAO), and the Artic Oscillation (AO) have played major roles on our winter weather. We simply have not seen any sustain blocking near Alaska and Greenland that would provide the United States a shot of really decent cold air. In a La Nina pattern, the jet stream is typically further north and produces wet weather across the Pacific Northwest and drier weather in the south. The NAO has been positive for almost all of the winter, which means we are unable to establish a blocking pattern that will allow the cold air to be pushed to the south and affect the eastern coast. Temperatures across the deep south were seeing temperature readings of over 70°F (21°C). Many areas should only see highs in the upper 40’s to low 50’s in the deep south.

Take a look at the record highs that were broken on February 1, 2012. 124 places broke their record high, with 27 areas tying their record high:

Broken record high temperatures on February 1, 2012. Image Credit: NCDC

January 2012 is listed as the 3rd least-snowy January for the contiguous United States since snow records began in 1966. December 2011 was ranked as the 11th least snowy on record. According to Dr. Jeff Masters, if February comes in four to five degrees warmer, then the winter of 2012 will have a great shot of becoming the warmest winter recorded across the United States. Masters also states that the top five warmest United States winters occurred after 1992, with the 1999-2000 winter season coming in as the warmest ever recorded.

Map of current watches and warnings on February 3, 2012. Image credit: National Weather Service

Speaking of no snow and cold, our friends in Alaska, and now Colorado, Nebraska, and Kansas would disagree. As of February 3, 2012, many areas across Colorado are experiencing blizzard conditions east of Denver. Many areas are expected to receive 12-18 inches of snow that will definitely cause major transportation issues. Some areas are already getting close to seeing 24 inches of snow. This storm could be considered the first significant storm for the 2012 winter season. The northeast had a snowstorm back around Halloween of 2011, but that never matched the intensity of this storm. Also, the western coast had significant snows in Washington as well, but most of these higher accumulations occurred in mountain areas. The storm system is very dynamic, and it will not only produce heavy snow, but it will likely trigger severe thunderstorms across the deep south in Texas and Oklahoma.

Here’s the risk areas for severe weather today:

Storm Prediction Center has issued a slight chance for severe weather across central and eastern Texas, Oklahoma, southwest Arkansas, and western Louisiana.

Will February bring cold air?

In my opinion, I just do not see any cold air pushing south across the deep south and southeastern United States. Weather models are hinting at a possible cool down by February 10-15, 2012. The more reliable model run, the European (aka ECMWF), simply does not show a lot of cold air across the country. The GFS model run, however, shows a big eastern trough in the long range models. For now, I am leaning towards the ECMWF. The northeast will likely see cold shots with a few storm systems affecting the region in February. However, snow lovers in the deep south will likely have to wait until next winter to see snow.

Will an early start to spring-like weather trigger another active severe weather season?

This is still too far out to tell. If the NAO stays positive during the spring months, and a highly amplified jet stream digs into the south, then it will be very possible for severe weather outbreaks. However, if the NAO becomes negative, then spring could become cooler than average and decrease our chances for severe weather. Whether or not the NAO will become negative is the biggest question all winter. Only time will tell, but as of now, it looks like severe weather will likely continue in the south where the cold air tries to push into the warmer, and somewhat unstable atmosphere. I do believe there is a decent chance a huge cold snap could occur in the spring which could cause problems for plants and flowers that have, and might I say, are currently blooming. Many areas in the south are already seeing flowers, grass, and trees growing due to the mild temperatures seen in January.

Bottom line: January 2012 was the third least snowy January ever recorded since snow records began in 1966. A monster snowstorm will produce at least a foot of snow across Colorado, Nebraska, and Kansas and will produce severe weather to the deep south in Texas/Oklahoma/Louisiana/Arkansas. Cold air has been dominant across Alaska all winter long with temperatures as cold as -60°F. As of now, Europe and even northern Africa are experiencing very cold temperatures as February begins. The only way this cold air will make it south and east of the Mississippi River is if the NAO becomes negative. For now, this remains to be unseen.

February 3, 2012

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