First frost and freeze of fall

Published 7:00 am Tuesday, November 24, 2015

We had our first frost and freeze of the fall on Monday morning.
Across most of the county, temperatures slid just below freezing for a few early morning hours before bright sunshine quickly warmed things back up.
Those out and about early saw most open, grassy spaces and the windshields of vehicles white with the season’s first frost.
Frost forms on cold, clear, calm mornings when the temperature of exposed surfaces cools to 32 degrees and colder. This can happen even when the official air temperature only cools to about 36 degrees. This is because the ground radiates heat faster than the air, dropping its temperature more quickly than the air immediately above it.
So, it makes sense that our first fall frost usually occurs before our first freeze.
This fall in Picayune, our first frost and freeze both happened Monday morning, Nov. 23.
According to statistics compiled by the National Center for Environmental Information, Nov. 4 is the average date for Picayune’s first fall frost, and Nov. 21 is the average date for our first freeze. That makes this year’s first frost later than most years, in fact, later than about 90 percent of all years. This first freeze, on the other hand, happened just about when it’s most likely to occur from year to year.
The cold snap was courtesy of a dome of cold, high pressure, which surged down through the Central Plains to the Gulf states from Canada. The same cold air mass, in conjunction with a low-pressure system, gave the upper Midwest their first big snow of the season. Ten to 20 inches of snow accumulated from South Dakota eastward through parts of Iowa, Wisconsin, Illinois, and Michigan.
Dominance of the high-pressure system in our area ensured that instead of white snow we saw plenty of bright blue skies on Sunday and Monday.
The high-pressure center moves off to the northeastern USA over the next few days. That will switch our winds around from the cold north to a much milder east and southeast direction. By Wednesday, and then through Thanksgiving and Black Friday, our first freeze will be just a memory, as our daytime highs climb back into the upper 60s to mid 70s. Overnight lows will only drop into the 50s or low 60s.
Overall, the weather should be pleasant for families and friends celebrating Thanksgiving day anywhere in Mississippi, Louisiana, Alabama, and Florida.
As of now, different computer weather models are coming up with a variety of solutions for the weekend as another cold front approaches from the west. Check in with the National Weather Service for an updated weekend forecast by typing in your zip code at
For those traveling outside of our adjacent states between now and Monday, you may encounter messy weather if you’re headed to the Central Plains states and westward. Heavy rains are predicted for parts of north Texas, Oklahoma, and Arkansas, and there even could be some ice as close as the Texas Panhandle and Oklahoma.
By Skip Rigney

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