Snow followed by clear and cool

Published 7:00 am Tuesday, December 12, 2017

By Skip Rigney

Winter made a grand entrance last Tuesday evening with the passage of a strong cold front. Then on Friday, Old Man Winter put on a performance to remember by blanketing Pearl River County with snow and setting a new record for coldest high temperature for the date.

Not surprisingly the northern portion of the county received the most snow. The National Weather Service’s snowfall analysis showed accumulations of four to five inches near and east of the I-59 corridor from Poplarville to Lumberton. In the southern part of the county several hours of sleet on Friday morning preceded the changeover to snow. Final accumulations by Friday evening were in the one to two inch range from Picayune north to Carriere.Temperatures  in Mississippi and across the Northshore in Louisiana hovered near or just above freezing all day Friday.

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The 43 degrees at New Orleans International Airport, which occurred just after midnight early Friday morning, was the coldest maximum temperature for December 8th since record keeping began there in 1946.

Four interrelated weather systems combined to spread snow from south Texas into Louisiana, Mississippi, Alabama, Georgia, then northeastward through the Appalachian mountains.

First a large dome of cold air spread over the eastern U.S. early in the week. Second, high in the atmosphere the strong west-southwest winds of the subtropical jet stream kept moisture streaming from the Pacific across the South.

Third, also several miles aloft, winds spun around a massive cold upper low pressure system centered in eastern Canada. On Thursday night and early Friday, a trough of low pressure and a shot of even colder air rotated around the Canadian low and approached the Deep South.

Fourth, a surface low moved slowly eastward across the southern Gulf of Mexico adding even more moisture and lift along the Gulf Coast.

The heaviest snow in Mississippi occurred in a band of six to seven inch accumulations stretching from Columbia northeastward to just south of Meridian. Mount Mitchell in North Carolina, which is 6,683 feet above sea level and located 30 miles northeast of Asheville, collected 25 inches of snow. This was the most widespread, heavy snow on record to occur so early in the winter in the South. Saturday’s bright sunshine quickly began melting the snow exposed to its warm energy. But, temperatures have remained cold at night and cool during the day, so snow in shady spots hung around until Monday, especially in the deeper snow in the northern parts of the county. This week will be quite a contrast. National Weather Service forecasters in Slidell don’t see any major weather disturbances headed our way until Sunday at the earliest. It will remain cool, however. Two additional surges of cold air are sliding southward along the eastern side of the large, trough of low pressure extending from eastward Canada southward over the eastern U.S. The first cold front will arrive today, the second on Thursday night. There will be very little moisture ahead of those cold fronts, so skies should remain fair except for a slight chance of showers Thursday night. Light freezes are expected tonight and Friday night. Otherwise, lows will be in the 30s and highs 55 to 65 through Saturday.