After the rains, spring has one final fling

Published 7:00 am Tuesday, May 23, 2017

By Skip Rigney

Rain has been the rule since Saturday, but a cool front is on the way that will sweep away the showers and give us what will likely be our last couple of days of spring weather for 2017.

Numerous showers and thunderstorms have been soaking Mississippi, Louisiana, and Alabama since Saturday. The National Weather Service Forecast Office in Slidell cited several ingredients for the heavy rain.

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A frontal boundary was slowly moving toward us from east Texas on Saturday. Since Sunday it has been stalled over Louisiana and Mississippi. Low-level winds tend to converge along such boundaries causing air to rise, moisture to condense, and showers to form.

There has been plenty of moisture to condense. The air from the surface up through very high altitudes has been unusually moist and humid. The instruments on the weather balloon launched on Sunday morning by the NWSFO in Slidell measured a total water vapor amount for the atmospheric column that was very near the record maximum.

Another factor contributing to this rainy period was the wind pattern high above us at altitudes of 30,000 to 40,000 feet. Several times since Saturday those winds above south Mississippi and Louisiana have created a chimney-like effect sucking up air from below.

Tonight, those ingredients for heavy rain will be replaced by a different weather feature. An unusually strong cold front for this time of year is surging to the southeast from the Great Plains.

Forecasters predict that the cold front will pass through Pearl River County sometime tonight.

As the cold front passes, the southerly winds that have been blowing moisture into our area since the middle of last week will shift to westerly and then northwesterly. Cooler less humid air will blow into the Gulf South.

Behind the front on Wednesday morning we may still have some clouds and a chance of showers, but by Wednesday afternoon the different feel in the air will be unmistakable.

Thursday will be a beautiful spring day with fair skies. Temperatures will climb from the early morning low or mid-50s to near 80 in the afternoon. The air will have a nice, dry feel to it, because dew point temperatures will have fallen from the 70s ahead of the front down into the 50s.

However, even as soon as Friday, and definitely by the weekend, it will once again begin to feel more like summer. Winds will shift back around to the south and southeast, and temperatures and humidity levels will begin their slow climb.

The NWS Climate Prediction Center in College Park, Maryland issues medium and long-range outlooks ranging from 6 days out to 90 days. CPC’s outlook for the northern Gulf Coast for May 29 through June 16 is that above normal temperatures are slightly more likely than below normal.

The long-term average temperatures in Picayune for that period climb from 65 to 69 degrees for lows and 87 to 90 degrees for highs.