BATON ROUGE, LA (WAFB) - Mainly sunny skies Wednesday will help afternoon temperatures climb into the mid to upper 50s for most of the WAFB area, but not everyone is finished with freezing temperatures just yet.
The National Weather Service (NWS) has posted another freeze warning for Thursday morning for much of our region. Unlike earlier Wednesday, Thursday morning's warning is limited to communities along and north of the I-10/12 and does not include Ascension and Iberville parishes. In fact, while the NWS has included fewer parishes in the freeze warning area for Thursday morning, it has extended the 'window' of time the warning will be in effect, running from midnight until 9 a.m. (compared to 2 a.m. to 9 a.m. for Wednesday's warning).
Regardless of whether your neighborhood actually dipped to freezing or not this morning, there's no denying that it was a very cold start to the day! Preliminary reports for Wednesday morning indicate the thermometer dipped to 32 degrees at Baton Rouge Metro Airport and down to 31 degrees at McComb (Pike Co. Airport) with a few additional SW Mississippi reports in the upper 20s. But, in just about all cases across the WAFB viewing area, the morning freeze was very brief and by 8 a.m., just about everyone was back above 32 degrees.
The winds eased overnight and early Wednesday morning just enough to let most of WAFB's northern communities get their first freeze of the season, but the coldest air didn't hang around long enough to so much as ice-over the bird bath. Based on preliminary reports from WAFB Weather Watchers and online weather stations across the region, it looks like few communities on the south side of the I-10/12 corridor reached freezing Wednesday morning - and if they did, it likely lasted for less than an hour. But, keep the heavy blankets handy as WAFB viewers can expect a near-repeat for Thursday's wake-up.
As Steve Caparotta notes, during many of these multi-day freeze events, the 'coldest' morning is often the second morning - after the chilling air mass has had time to settle over the area and after the winds have backed down. With these Arctic and polar air masses, the winds often remain elevated for a number of hours after the front moves through. Higher winds keep the lower levels of the atmosphere well mixed and that can reduce how quickly the air temperatures fall.
Why are winds important? Overnight and into the pre-dawn hours - especially under clear skies - the air becomes coldest right along the ground surface and is warmer as you climb in elevation above the ground. (Remember, the air temperature that we report for our weather stations is typically measured roughly five feet above the ground.) Under light-wind to calm conditions, the air temperature at the lower levels of the atmosphere steadily falls as the ground cools. But when the winds pick-up, the warmer air from above is constantly being mixed downward with the air near the ground slowing the rate at which the air in the lowest levels can cool.
That brings us to our Thursday morning freeze warning. Overnight and early Thursday morning, winds will be lighter than those Wednesday morning. The morning skies will be clear once again and Thursday will be the second day of the season's first real chill – all factors pointing to a good chance for a colder start on Thursday morning compared to earlier Wednesday morning.
What will limit how cold it gets on Thursday morning is that the core of the coldest air will continue to track farther to the east through Wednesday afternoon and night. Based largely on that, we're thinking WAFB viewers well to the north and east of metro Baton Rouge should prepare for a slightly colder - and longer - light freeze for Thursday morning. For metro BR, we can expect something similar to what we experienced Wednesday morning, while many viewers to the west of the Capital City may miss out on a Thursday freeze altogether.
In the end, regardless of where you live in the WAFB region, Thursday's chill will be nothing of serious concern - just another very cold start to the day. Check the pets and the tender plants. Again, there are no worries about the pipes. And by Thursday afternoon, we'll be back into the 60s and saying 'goodbye' to the winter-like temperatures. A warming trend kicks-in that will deliver afternoon highs in the 70s for Friday, Saturday and Sunday!
Say 'hello' to the first of what will be many rides on our winter-weather roller coaster!