Here we are nearly two weeks into the month of March and we currently sit at more than seven degrees above long term averages. This includes five days with above average highs.. all in the 50's and 60's..two of which already broke records this last weekend. Snowfall early in the month supported cooler temperatures, but that has long since melted, and moving forward through the next week or longer, we will be flirting with more record warmth. The pattern that is developing will bring very warm air to much of the nation east of the Rockies in the coming days. Hundreds of record highs are likely over the next week to ten day stretch from the Plains eastward through the Great Lakes, Ohio Valley to the east coast. Here are some of the Eau Claire records in jeopardy in the coming days..
March 14: 66/2010
March 15: 70/1927
March 16: 73/1930
March 17: 75/1894
March 18: 71/1910
March 19: 74/1910
March 20: 67/1938
Here is a look at the Climate Prediction Center's temperature outlooks for the 6-10 day period, 8-14 day period, and for the entire month of March. The maps outline the probability of whether or not temperatures averaged out over that period will be above or below average, or near normal. You can clearly see the bullseye over the mid-Mississippi River Valley where the highest probabilities of above average temperatures are forecast. Western Wisconsin, though not in the heart of it, remains in a 50% or greater shading through the next two weeks.
If these forecasts hold true, the combination of warm days and mild nights during this two week stretch will clearly put this March into the running for the warmest on record. According to the National Weather Service data, the warmest March on record since 1949.. is 1973.. with an average temperature of 39.7.. roughly 10 degrees above the 30 year long term averages at the time. We came close to that in 2010. Of course many want to know what is causing this unusually warm weather. There are several factors, including the ones which helped to bring us the 5th warmest meteorological winter (Dec-Feb) on record here in Eau Claire. These include the phases of the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and the weakening 2nd year La Nina event. They are still in play. Another factor is the lack of snow cover across the northern tier of states. Here's a look at the latest snowfall coverage area map.. very little snowpack exists anywhere in the states, minus the inter-mountain west, far northern Wisconsin and northern New England.
Snowpack would still be expected to reside in the northern states this time of year, and helps to keep temperatures on the cooler side, even when warmer patterns develop. This is why you will likely never see record high events this time of year when there is a fairly significant snow cover to our south and/or west. Finally, one of the largest players is the positioning of the jet stream. Here in March the average position of the jet would still be expected to reside somewhere across the northern third of the nation. This has hardly been the case however most of the winter. Other than a few occasions, it has been much further north, many times in southern Canada, which led to the mild winter across most of the U.S. Arctic air to the north wasn't able to push southward into the states.
The current evolving pattern is one that becomes a bit more common as we move through the spring and sometimes the fall months, when the seasons are making the transition from warm to cold or vice versa. The jet can become what we call, highly amplified, where a large ridge/trough configuration develops. In this case, the longer range guidance is suggesting this pattern will evolve into what is known as an "omega" block.. it's appearance gives the name away, if you know your Greek alphabet. The forecast map below is at jet stream level next Monday, March 19.
These patterns are slow to break down, commonly lasting a week or more. Those fortunate enough to fall under the "ridge", an area of relatively warmer air in the upper levels, will typically experience mostly warm and dry weather.. but for those under the "trough", much cooler and unsettled weather can be expected. I'm guessing this pattern will be getting some national attention over the next week or longer, with record-breaking warmth in the eastern half to two thirds of the country, (including us..) while out west, late season snows will fall in some unusual places.. including southern California and Arizona..
The next logical question would then be.. so does this mean winter is over for good and the cold is gone for the season? Not so fast.. we have to remember it is still only the middle of March. Keep in mind we average more than 8 inches of snow this month, while April typically sees just over 2 inches.. Is it possible? Yes.. Likely? No.. But, only time will tell in what has been an anything but typical year weather-wise thus far..