A couple of winter threats ahead. Sunday night into Monday night looks significant.
We are looking over the latest weather data as it comes in late this Thursday evening, and models continue to lock onto a couple of different winter weather threats across the Tennessee Valley over the next few days. With us now getting closer in time, the arctic air already being in the area and not going anywhere, and the models converging on one solution instead of disagreeing, we are getting more confidence. Let's break this down...
Possible Event 1: Friday night into Saturday
Light to moderate rain spreads north across the area after midnight tomorrow night into the predawn areas of Saturday. With the arctic air in place, we think some of this has a decent potential to switch over to light freezing rain or freezing drizzle. The exact area where this happens is still a little tricky. Our high-resolution Baron model here from the afternoon run has that setting up mainly over our Tennessee and Mississippi counties. However, other computer models are colder across northwest Alabama as well, and even this model has been trending colder with time as we've gotten closer. So, don't get caught up in the EXACT area of the rain/ice line on these Futurecast images. This continues through the midday and into the early afternoon hours before temperatures everywhere get warm enough that things switch over to all rain.
This first event looks to be a relatively minor event as these things go. Ice accumulations generally look to be under 0.10", which is usually the criteria that triggers a Winter Weather Advisory from the National Weather Service. However, we can't rule out a few isolated spots with 0.10-0.15" accumulations. That is enough to cause some bridge icing and some minor icing on small tree limbs. The temperatures look marginal enough that surface roads may stay okay with this first round. And the accumulations look light enough that power outages should not be an issue with this one. You typically need accumulations over a quarter inch for power problems, unless there is significant wind. We don't expect either with this first round. Even though accumulations look light, you STILL have to be careful if you travel. Thursday in the Ft. Worth area taught us that. That massive pile-up out there happened with only light freezing drizzle and very light ice accumulations. It takes barely any ice accumulation at all to cause travel issues.
Possible (but becoming more likely) Event 2: Sunday night through Monday night
This is the one that has our attention the most. This one has always held significant POTENTIAL, but for days, the models have been in loose agreement, but not much. As we have gotten closer though, all the models have started locking on to one scenario, and it's giving us increasing confidence that this may be a significant, potentially high impact type icing event for all of our viewing area.
Temperatures all day Sunday look to stay near or just below freezing across the Tennessee Valley area, and with cold temperatures between now and then, we are cooling down the pavement temperatures and other infrastructure, making it easier for wintry precipitation to accumulate. The first wave of this second event overspreads the area after dark Saturday evening through the morning hours of Monday. Temperatures will be dropping into the 20s across the area. Precipitation intensity looks to mainly be light to moderate, but with temperatures so cold and the precipitation being steady, it will be easy for significant accumulations to occur.
Temperatures 3,000-5,000 ft above the ground will be above freezing, meaning that this will NOT be a snow threat. I repeat, and hear me good instead of just hearing what you want to hear, this will NOT be a snow threat. This will be freezing rain... rain that falls as liquid but freezes on contact causing a glaze of ice. Snow falling out of the clouds will melt as it encounters that above-freezing air. Once a snowflake melts, it can NEVER become a snowflake again. It either falls as sleet if it is able to refreeze on the way down, or it falls as rain... and then it remains rain if the surface temperature is above freezing or freezes on contact as freezing rain if surface temperatures are at or below freezing. This will N-O-T be a snow threat for our area.
By midday on Monday, we may get a very brief break, but temperatures will stay below freezing. By afternoon, the second more significant round of wintry weather will then move into the area from the west, lasting into the overnight. Temperatures will drop out of the lower 30s back into the 20s as this happens, and this precipitation looks even more widespread and heavy than the predawn/morning round. Whatever ice accumulations there are from the early activity will not melt and will only be added onto by the afternoon and overnight freezing rain. Before all is said and done, significant ice accumulations are very possible areawide across the viewing area. While it is still too soon to talk about exact amounts, this looks like a potentially significant and high-impact threat across our entire viewing area, with travel impacts likely and power outages possible. A lot of people have already asked if this will be like the ice storm in 1994. That event was an ice storm that lasted over multiple days and ended up with ice accumulations near 2 inches. We don't anticipate anything like that. This simply won't last long enough to be THAT high-end. However, there is increasing confidence that this will likely be an event that has significant accumulations to cause widespread travel and power issues, similar to what Arkansas and the Memphis area just saw Wednesday night into Thursday morning.
Ben will be on the Facebook page and on the channel with a fresh forecast update in the morning. We will have a team conversation at midday when I get into the office, and if the morning data still looks as it does tonight, we will be sounding the alarms on a potential high-impact ice event for our area. The National Weather Service usually issues a Winter Storm Watch between 36-48 hours ahead of an event like this. With a start time of Sunday night, that means a Winter Storm Watch is likely to be issued either Friday afternoon or early Saturday morning.
Be sure to keep checking back for details as we continue to work out the exact details of this forecast, but the overall message is that confidence is increasing on the POTENTIAL for a higher impact event areawide across our viewing area Sunday night through Monday night.