Freeze possible Saturday night

Published 11:52 am Saturday, March 12, 2022

By Skip Rigney

The weather on three consecutive days cannot be much different than the last three in south Mississippi.

Thursday could have been ordered up by the Greater Picayune Area Chamber of Commerce. Blue skies and gentle breezes. A cool morning and a mild afternoon with low humidity. A maximum temperature of 75 degrees. Who could ask for better weather?

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Less than 12 hours later, Pearl River County residents awoke to clouds and showers Friday morning as a warm front crawling northward from over the Gulf pushed loads of moisture onshore. Although most of the day was dry, by Friday afternoon a cold front was rushing southward to meet the warm front, and a center of low pressure was moving eastward from Louisiana into Mississippi. That complicated mess of meteorological systems resulted in an extensive precipitation shield across the state Friday evening.

The low pressure and its associated frontal systems continued racing towards the Atlantic coast Friday night. On the western backside of these systems cold air rushed into the state, arriving in north Mississippi before all the precipitation had departed, turning rain to sleet and snow in Oxford, Tupelo, and Corinth.

High pressure from Canada plunged southward down the central Great Plains. The difference in atmospheric pressure between the low pressure system exiting to our east and the high pressure system arriving from our northwest resulted in strong winds, prompting the National Weather Service in Slidell to issue a wind advisory for inland areas and gale warnings for offshore for Friday night into today (Saturday).

Today and tonight the coldest air mass to invade Mississippi since early February will continue to pour into the state. Even though it will be sunny, brisk winds will make Saturday seem colder than indicated by the actual temperatures of 40s and low 50s.

Once we lose the warmth of the March sun, temperatures will plummet. Forecasters expect them to fall to near freezing by midnight. How low they drop by Sunday morning will depend largely on the wind. Higher wind speeds will mix down air from a warmer layer at altitudes 1,000 to 10,000 feet above us, which would keep Sunday morning’s low near 30. Lower wind speeds won’t mix the warmer air from higher altitudes down to the surface, which could result in temperatures near ground level where we live to cool into the middle 20s.

As is typical for early spring, this cold snap will be short-lived. Abundant sunshine on Sunday will warm us to near 60 degrees, and Sunday night is forecast to be a good ten degrees warmer than Saturday night.

By Monday, the centerline of the Canadian high pressure will progress to the Atlantic coast, putting us on the western side of its clockwise circulation. Southerly winds will replace the weekend’s Canadian cold with milder, more humid air from over the Gulf of Mexico.

Monday night and Tuesday a low pressure system is forecast to drop southeastward from Oklahoma toward Mississippi.

As the low destabilizes the atmosphere and taps into the mild, humid air from the Gulf, there could be a few strong thunderstorms embedded among numerous showers.

From postcard perfect, to rain, to fair and freezing, to showers and thunderstorms, just consider it another typical week of March weather in south Mississippi.