Freezing rain with light ice accumulation possible both tonight and again Tuesday night.
A WINTER WEATHER ADVISORY has been issued for some of our southern middle Tennessee counties. This includes Hardin, Wayne, Lewis, and Maury Counties of Tennessee in our viewing area, for the potential for light ice accumulations tonight into Tuesday morning that may reach up to 1/10th of an inch. This advisory is valid from 9:00 PM tonight through Noon Tuesday for the first of two rounds of light freezing rain that will affect our area overnight tonight and into Tuesday morning. It is important to note that an additional Winter Weather Advisory will likely be issued across the area (possibly to include even more counties) for the second round of wintry weather that is scheduled to affect our area tomorrow night into Wednesday morning. This will likely be issued as we get a bit closer to that timeframe. Of note is also the issuance of an ICE STORM WARNING back across west Tennessee, far northwest Mississippi, and into eastern and central Arkansas. This is just to the west of our viewing area, and this is the area where higher impact ice accumulations are likely (a quarter to half inch accumulations or greater). Even when adding both periods of light freezing rain together, this is NOT expected to be a major ice storm for our area, but some light ice accumulations that may cause slick travel (especially bridges and overpasses) are definitely possible. While it's not especially likely, we also can't rule out at least some isolated short-lived power outage issues.
Here's the breakdown of everything with Futurecast. Temperatures this morning are starting in the upper 40s and lower 50s with a few lingering showers. These will exit off to the east as we head through the morning. Off to the northwest, sub-freezing air is nosing southward into northwestern Tennessee, and this will continue to move gradually southward through the day. However, ahead of the colder air, daytime highs over the area look to at least briefly climb into the mid 50s. That will be short-lived as the freezing line continues to drop southward over western and middle Tennessee as we head into the evening.
By the early evening, a few spotty showers start to break out over our area before a more widespread area of light to moderate precipitation approaches from west Tennessee and north Mississippi near and after midnight. This overspreads southern middle Tennessee and north Alabama going into the early morning hours of Tuesday. As this happens, temperatures over middle Tennessee continue to drop, and by 12:00-2:00 AM, the freezing line looks to drop down to near Highway 64 in southern middle Tennessee... or at least southward to a Savannah to Waynesboro to Summertown to Columbia line. As this happens, that rain will begin to switch over to light freezing rain. That continues on through the early morning hours. By 4:00-6:00 AM, the freezing line may make it as far south as Lewisburg to Pulaski to Loretto to Cypress Inn, and it may even flirt with western and northern Lauderdale County AL or northern Tishomingo County MS. However, by this time, the precipitation will be much more spotty and very light. Still, spotty areas of light freezing rain or freezing drizzle will still be possible. The light precipitation will continue through 8:00-9:00 AM before winding down and moving out by 9:00-10:00 AM or so.
With this first round of light freezing rain, Futurecast is showing light ice accumulation being possible over much of southern middle Tennessee, with totals along and north of Highway 64 possibly being as high as 1/10th to 1/15th of an inch or so. There are even trace amounts of ice accumulation on Futurecast as far south as Iuka, MS and Waterloo, AL. With temperatures mainly in the 30-32 degree range as this happens, this would mainly cause slick travel on bridges, overpasses, and hilly areas with higher elevations. However, given the light nature of the precipitation over several hours and less of a chance of it to run off before freezing because of the light intensity, there may be enough accumulation on tree limbs or power lines to POSSIBLY cause isolated and/or short-lived power issues, especially closer to the Highway 412 corridor of middle Tennessee. Amounts these light generally are not heavy enough on tree limbs and power lines to cause major or long-lived power disruptions without really strong winds also in place, however. And with temperatures generally staying above the 20s, it is much less likely that surface roads and highways (especially the busier ones) would see ice accumulation.
The forecast starts to get a little more tricky as we head into the afternoon hours of Tuesday. Other high resolution models hold off Round 2 of precipitation until the evening hours, but Futurecast starts moving it in by 1:00-2:00 in the afternoon. However, as this happens, Futurecast also shows temperatures over southern middle Tennessee warming into the mid 30s and above freezing in the 2:00-4:00 PM timeframe. If these temperatures warm into the 32-36 degree range in the afternoon, whether it stays dry or whether precip does move back in, that would increase the chance of some MELTING of the ice that accumulates tonight into Tuesday morning in these areas. That is important because if there is a period of melting Tuesday afternoon, that would DECREASE the overall ice load on tree limbs and power lines once we add the second round of light ice that will happen Tuesday night into Wednesday morning. That would decrease the chances for power disruptions, especially more widespread or longer-lived outages.
However, if Futurecast is a little too warm with the afternoon temperatures and any areas stay 31 degrees or lower through the day, that would not allow melting, and whatever ice accumulates Tuesday night into Wednesday morning would be added to light icing that had already accumulated tonight into tomorrow morning. If this happens instead, it would increase the chances of power outages for those areas by the time we add in the light ice accumulation from Tuesday night into Wednesday morning.
The worst case (but least likely) scenario would be that Futurecast is right about Round 2 starting in the early afternoon instead of the evening BUT it is too warm with temperatures and portions of the area remains below freezing while that moves in. Again, that is the least likely scenario, but should it happen, that would further increase ice totals when adding both rounds of wintry precip together, and that would further increase the chances for power outages across the area. That is the least likely scenario, but even the higher resolution models don't always handle these shallow arctic air masses correctly, and the WRF models run by NOAA hinted that there may be some areas near Highway 412 that never get above freezing Tuesday afternoon. We will have to watch that closely!
Regardless of whether Futurecast is right with the second round of activity starting in the afternoon, or other models are right with it holding off until the evening, the second round will be a bit longer in duration and will be a bit more steady as we go through the overnight Tuesday night into the morning hours of Tuesday. This, combined with the idea that temperatures Tuesday night will be a touch colder than tonight and will arrive at the freezing mark as early as sunset over southern middle Tennessee, means that the potential for light ice accumulations will be even greater Tuesday night than they will be tonight, and they will likely be a bit more widespread. While our official forecast for now calls for the ice accumulations to mainly stay north of our Alabama counties, there are some normally reliable high-resolution models that get the freezing line south of the Tennessee River in northwest Alabama by early Tuesday evening. We will have to watch that carefully because, like we've mentioned before, even the high resolution models often have a hard time handling these shallow arctic air masses and they usually don't end up far enough south with them compared with what happens in reality. Futurecast also has areas near Highway 412, especially Hohenwald and westward, flirting with the upper 20s overnight Tuesday night into early Wednesday morning. Temperatures falling into the upper 20s would increase the chances of power outages and it would increase the chances of slick spots on surface roads, especially in the hilly areas with higher elevation. Futurecast has off and on showers continuing through a large part of Wednesday, but it has temperatures climbing above freezing and into the mid to upper 30s by late morning and midday. That means that, regardless of who gets ice accumulations, there will be areawide melting and thawing by late morning and midday, with improving travel conditions.
After adding in the light icing from Tuesday night into Wednesday morning, Futurecast shows overall storm total ice accumulations of 0.10 to 0.30 of an inch as far south as southern Hardin, Wayne, and Marshall Counties and north/western Giles Counties of Tennessee. However, this does NOT take into account the potential for temporary melting Tuesday afternoon when temperatures may briefly climb above freezing for a few hours. That means that these storm total amounts may not represent what is accumulated on trees, power lines, elevated road surfaces, etc., as we come out of Tuesday night and head into Wednesday morning. These numbers would only represent the amounts actively on trees, lines, bridges., etc., if there is no melting Tuesday afternoon. ANY amount of ice accumulation is a problem, especially for the potential for slick travel, but if there is temporary melting Tuesday afternoon, that would decrease the chance of widespread or longer-lived power outages across the area as we head through Tuesday overnight into Wednesday morning.
When it comes to icing events, this definitely does look to be impactful, but it looks to be on the lower-end of ice events and more of a "nuisance" type event instead of a major ice storm. As mentioned, ANY amount of ice can be a problem. It takes just a trace of ice to make things slick for driving or for walking. Criteria for an "ice storm" is ice accumulation of 1/4 of an inch or greater. There is some potential that when we add the totals from both rounds together, we may reach those numbers in a few areas. That would be even more possible if there isn't much melting Tuesday afternoon between rounds. However, this will NOT be like those major, historic ice storms you may have lived through in the past... events like 1994, events in the 80s, etc. This is NOT that. Just like tornadoes or hurricanes, there's a spectrum with winter storms too. A small EF0 that rips a few shingles off your roof is still a tornado, but it's not in the same universe as a big EF4 or EF5 that might level your well-built home down to the foundation. The same works with "ice storms" and "snowstorms". You might reach that 1/4" accumulation criteria, and the event be officially called an "ice storm" because of that on a technicality, but this will NOT be the same as those big historic ice storms of the past. Those events that stick out so vividly in your mind and make you justifiably nervous when you hear "ice" in the forecast had accumulations of 1 to 2 inches (or more in some cases). Those were rare, high-end, crippling events. This is much more of a short-lived "nuisance" type event, even though it will likely be impactful, especially in terms of slick travel on elevated road surfaces (bridges, overpasses, hilly areas, etc.,). Don't shrug it off just because it's not going to be a crippling event, but there's also no reason to be afraid of it either!
Travel is discouraged during these periods where there may be icy spots and slick travel. Unlike snow, there is zero traction on a glaze of ice. It is also very hard, if not impossible, to pre-treat road surfaces for ice because this falls as liquid rain and then freezes onto contact surfaces that have a sub-freezing temperature. That means that treatment chemicals and solutions are likely to be washed away before they can do their job effectively. However, we do realize that some people have to travel and are in a situation where it is unavoidable. If you are in that situation, please just take it slow and allow extra time to reach your destination, allow extra following distance between you and a vehicle in front of you, avoid sudden stops as much as possible, and steer in the direction of the skid if you start sliding so that it is easier for you to regain control of your car.
We will have adjustments to the forecast and live updates as needed as the situation unfolds over the next couple of days. Please stay in touch with updated weather information so that you can be prepared and plan accordingly.