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Hard freeze possible Monday night

By Skip Rigney

Writing this column feels like deja vu. Three of the themes from last Saturday are still major topics this week. First, bitterly cold air is still lurking nearby. Second, there is an outside chance for wintry precipitation when the coldest air finally arrives. Third, the computer weather models that are the cornerstone of modern forecasting continue to do a poor job handling the southward movement of the arctic air.

One thing which the models did get correct was the development of a large area of low pressure several miles above Canada. This past Monday its counterclockwise swirl of winds covered over one-half million square miles from Hudson Bay, Canada, to the Great Lakes.

The center of the low is now located just north of Minnesota. The winds on its western side keep sending reinforcing surges of cold surface air down the Great Plains. Although it has been a slow process, the frigid air has continued to ooze slowly southward. Amarillo, Texas, began the week near 60 degrees, but by Tuesday morning had slid into the teens with the added bonus of freezing fog.

The cold front marking the leading edge of the polar air finally made it through south Mississippi on Thursday evening preceded by strong thunderstorms and rain. Rainfall totals varied from one to 3.5 inches across the county, with the heaviest rain Thursday indicated by radar between McNeill and Crossroads.

The cold front has become stationary in the Gulf to our south and over the Florida Panhandle to our east. Its close proximity will affect our weather in two ways. First, although we will be cold, the freezing air will remain to our north and west through Monday. Secondly, a plume of moist air from the southwest being lifted aloft in a zone behind the nearby front will keep a chance of showers in the forecast this weekend.

On Monday a potent disturbance in the upper atmosphere will swing through Texas then race northeastward. This will increase our rain chances Monday.

Temperatures in the rain here in south Mississippi during most of the day Monday will be chilly, but above freezing. However, as the disturbance pulls away, frigid air to our northwest will surge southeastward, and our temperatures will plummet.

Will freezing temperatures arrive before the rain departs from Pearl River County? As of now, it’s too close to call. If it does, we could see sleet, or even worse, freezing rain late Monday afternoon or night. Even without freezing rain, flash freezing of standing water on roads could create black ice problems for motorists.

Snow is unlikely because temperatures several thousand feet above us will probably remain above freezing even after temperatures near the surface drop below freezing.

Regardless, a hard freeze is likely Monday night and early Tuesday morning. Check online at www.weather.gov/LIX during the day Monday for an updated forecast.

That’s just the beginning of a wild weather roller coaster ride. Another freeze is possible Tuesday night. Then, temperatures will warm briefly during the middle of the week and another cold front will kick off showers and thunderstorms Wednesday or Thursday.

Behind that cold front we have another brief chance of wintry precipitation and more freezing temperatures.

Buckle your seat belts.