Currently a large trough is pushing its way across the Plains where severe weather will begin to pick up this afternoon into the overnight. This will surely add to the tornado totals as a large area from Texas northward to almost the Canadian border could see tornadoes, large hail, and damaging winds today. The threat will push off to the east tomorrow, though it is expected to be less intense than today.

Following the exit of this system though, what does the rest of March have in store? Taking a look at the 8 to 14 day temperature outlook from NCEP, temperatures will be well above normal for most of the lower 48 to end the month. The only areas of exception are Alaska, which continues to be colder than normal this winter, and the west coast.
The reasoning behind these much above normal temperatures across a majority of the nation is constant ridges which will be in place over the center part of the nation. This will allow for warm air to infiltrate these areas. The 8 to 14 day 500 mb heights and associated anomalies are shown below.
With all of this warm air in place to end the month there are sure to be more high temperature records that will fall but, this also implies that severe weather may be kept to a minimum. Troughs are typically associated with severe weather and with ridges occurring across the center of the nation, severe weather will not find many places to form across the nation. This means that after this current storm system moves through, the rest of March may in fact exit like a lamb.
However with all of this warm air in place, if a shot of cold air could be pushed into the United States, severe weather would result. Currently the NAO is positive, as it has been for much of the winter, which has caused the jet stream over the United States to be much farther north than normal. This has trapped most of the truly cold air north of the United States. Models are beginning to show signs that this trend could be coming to an end, at least temporarily. Pictured below are the NAO observed values and forecasts for the rest of the month. The forecasts are agreeing that the NAO value should decrease as we head toward the end of this month but near the end of the month forecasts diverge, with some forecasting another increase and some continuing the decrease. If the NAO value did decrease, colder air would be able to push into the United States around the start of April which means despite March going out like a lamb, April may come in like a lion. This is definitely something everyone should keep an eye on as it gets closer.
Until then though, enjoy the nice weather that will be across much of the nation to end the month. With the GFS model showing few storm systems moving through, except along the northern edge of the country where the jet stream will be residing, most of the nation will experience above normal temperatures and sunny skies.