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Showers Sunday, more rain later in the week

By Skip Rigney

National Weather Service (NWS) forecasters say that the New Year is likely to get off to a soggy start from the upper Texas coast to south Mississippi.

Meteorologists at the NWS’s Weather Prediction Center in College Park, Maryland, analyze large-scale weather patterns and computer model trends in order to provide forecast guidance to local NWS offices across the country. They pay special attention to the winds and circulation patterns three to seven miles above the earth where the jet stream is located. For several days they have watched as the computer models have predicted that a low pressure system with strong winds would drop southward above the west coast of the U.S. and then combine with high winds roaring above the Pacific and over northwestern Mexico.

That energy will move eastward causing strong rising motion in the atmosphere below. With plenty of low-level moisture available from the Gulf of Mexico, that sets the stage for heavy rainfall.

In their forecast discussion issued early Friday, the forecasters wrote, “expect a period of widespread showers and thunderstorms across portions of the western/central Gulf Coast and lower Mississippi Valley, with the potential for areas of heavy rain extending northeast to some degree as well. While confidence is not yet great for precise timing and duration, there is a decent signal for a meaningful rainfall event over this general area.”

This was echoed by forecasters at the NWS office in Slidell when they noted in their local forecast discussion that, “The next system is expected to push through Thursday and Friday of next week. Still some uncertainty with timing and speed of the next system but rain chances will be high.”

Once the showers do get here, WPC’s best estimate for rainfall totals in south Mississippi is in the 1.0 to 2.5 inch range.

It appears that Monday, New Year’s Eve, and probably New Year’s Day will remain dry. But, as pointed out by the NWS, there is more than the usual uncertainty as to when the showers will arrive. So, it would be wise to check for forecast updates if you have plans that could be impacted by weather on Tuesday or Wednesday.

Before we get to the main course later this week, we’ll get an appetizer on Sunday with showers and possibly a few thunderstorms. Rain from Sunday’s system is expected to be relatively light, with one-tenth to one-half inch likely.

Sunday’s showers will be set off by energy associated with low pressure centered today over Colorado. By Sunday the low will be near Minnesota, sucking a plume of mild, humid air northward from the Gulf of Mexico, over us, and all the way to Chicago.

At the same time the counterclockwise circulation around the low will be blowing cold air southeastward from Canada across the Great Plains toward us. The leading edge of the cold air is predicted to reach Pearl River County late Sunday afternoon or early Sunday evening.

That cold front will spell the end of a six-day stretch with high temperatures above 70 degrees. Monday’s and Tuesday’s temperatures will cool off to near the late December historical averages of lows near 40 and highs near 60.