Record warmth to ease as March begins

Published 7:00 am Tuesday, February 27, 2018

By Skip Rigney

historically warm air mass has immersed much of the eastern one-third of the United States since mid-February. High temperature records have been broken on multiple days from Louisiana all the way to Maine. Some of the records in the Northeast U.S. were broken not just by a degree or two, but were smashed by five or more degrees.

We got in on the record-setting action here in Pearl River County. According to the Southeast Regional Climate Center, three record high temperatures were set in Poplarville at Mississippi State University’s South Mississippi Branch Experiment Station. A new record maximum temperature for February 17th of 81 degrees broke the old record of 80 degrees set in 1980. The high of 80 on February 22nd tied the records set in 1997 and 1949. Last Friday’s high of 82 broke the previous record for February 23rd set in 2006.

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The entire month has been warm. Across south Mississippi, temperatures have been well above the historical averages all but three days this month. Just how extreme the warmth has been is shown by the fact that the daily average temperature has been warmer than 13 degrees above the historical average on 11 of the first 25 days of this February.

As is often the case when one side of the country is very warm, the other side of the country was in the deep freeze. Last week when we were in the 80s, Rochester, New York, was also an unbelievably toasty 75 degrees. Meanwhile in the cold air over the western U.S., temperatures in Montana were struggling to make it out of the single digits after starting below zero in the morning.

Meteorologists refer to the upper wind, pressure, and temperature pattern associated with these sharp west to east temperature swings as “highly amplified.”

A large trough of low pressure in the upper atmosphere in the western U.S. is matched by an equally large ridge of high pressure over the eastern U.S..

The upper high pressure system has been weakening over the past several days. This will open the door for an upper trough of low pressure to roll westward above the Great Plains and Mississippi Valley on Thursday. Near the upper trough and its associated surface cool front on Thursday some showers and thunderstorms are likely for our area.

Computer weather models indicate that the upper trough will move far to our east on Friday, and high pressure will quickly begin to rebuild at several miles altitude above the Gulf of Mexico northward to the Great Lakes.

That high pressure provides the promise of a mild and mostly sunny weekend ahead. The surface air mass behind Thursday’s front will be cooler and much less humid than what we’ve seen since Valentine’s Day. This will allow morning low temperatures to fall into the 40s for early Friday and Saturday. Afternoon high temperatures on those days are forecast to be near 70. That’s close to average for early March in Pearl River County. For record keeping purposes, meteorologists and climatologists define December through February as winter and March through May as spring. For us the beginning of 2018’s “meteorological spring” will actually be a little cooler than the end of “meteorological winter.”