Risk for Severe Weather Tomorrow (3/19/2018)

NOTE: This blog post is pertaining to the sever weather risk for MONDAY, MARCH 19th, 2018.

Spring is the most common season for severe weather to occur in West Tennessee. March, April, and May are when severe thunderstorms are most frequent and this probably comes as no surprise since we had multiple tornadoes, damaging wind, and large hail storms come through around this time last year.

Tomorrow will bring an opportunity for severe weather to return.

All of West Tennessee is under a risk for severe weather, but the threat becomes more serious the closer to the Tennessee River you are. Our western counties near the Mississippi River are under a marginal risk (1 out of 5). Most of our viewing area is under a slight risk (2 out of 5) and this can be seen as the area colored in yellow. The enhanced risk (3 out of 5) is for parts of Benton, eastern Henderson, Decatur, and most of Hardin counties which includes Camden, Holladay, Darden, Parsons, Decaturville, Scotts Hill, Sardis, Bath Springs, Saltillo, Savannah, Olivehill, and Counce.

Now before we dive into threats, lets talk about timing and when you should be weather-aware tomorrow. 

9am to 5pm

I know. That's a large window of time, and severe weather won't be occurring during this entire time, but for the 21-county area of West Tennessee, those are the hours your Storm Team will be most vigilant. It's the duration of time that the "door" will be open for storms to move in. I've seen on Twitter that some schools in Alabama are already going to be dismissing early tomorrow. I hope that's not the case here! The timing in the storm threat just doesn't make putting students on buses a smart idea.

Regarding the potential threats, here's what the situation looks like. We forecast multiple ingredients when it comes to deciding what threats are likeliest. Ultimately, we need three important things - moisture, energy, and a lifting mechanism. We have a strong lifting mechanism in an area of low pressure, and a decent amount of moisture, but the amount of energy remains a little uncertain. Temperatures will be warming up to the upper 60s and lower 70s, but the more likely potential for any energy to create severe weather will be farther to our south and east across northern Mississippi, northern Alabama, and Middle Tennessee.

Another important ingredient for severe weather includes wind shear which can be described as a change in speed of the wind and direction of the wind with height. There will be plenty of that, but without a trigger or enough energy this factor becomes less important.

Given the parameters, large hail seems to be the most likely candidate for a severe thunderstorm on Monday. Showers and thunderstorms will be starting out in individual cells, and when a thunderstorm is its early stages, large hail is a common threat. Damaging winds are possible too but fall second to hail in this case. An isolated tornado will be possible as well, but especially south of I-40 in the area highlighted in yellow below...



...and if a tornado is going to develop, it's more likely in the afternoon than in the morning.


Here's the good news!

The area of low pressure responsible for this threat for severe weather looks as though it's taking a more southward track. This means, our energy levels could be limited, preventing thunderstorms in West Tennessee from becoming too strong. 



The new data coming in certainly seems to be trending in this direction. Let's hope that that's how things turn out! Meteorologist Corallys Ortiz will have an update on the forecast on WBBJ 7 Eyewitness News at 10! 


SUMMARY

• BE WEATHER AWARE TOMORROW FROM THE LATER HOURS OF THE MORNING THROUGH THE AFTERNOON
• CHECK WITH US FOR ANY CHANGES TO SCHOOL SCHEDULES
• IF A THUNDERSTORM BECOMES SEVERE TOMORROW, THE MAIN THREAT IS LARGE HAIL WITH A SECONDARY CONCERN FOR DAMAGING WINDS AND AN ISOLATED TORNADO
• BEST CHANCE FOR A TORNADO IS IN SOUTHWEST TENNESSEE DURING THE AFTERNOON
• THE TREND IS FOR THE SEVERE WEATHER RISK TO BE LOWER
• UPDATE ON WBBJ 7 EYEWITNESS NEWS AT 10

Winter Storm Review

NOTE: This blog post is pertaining to the winter weather that occurred on Friday, January 12th, 2018.

Some locations accumulated a little more snow than expected today but most of the area received what we expected. Jackson, Lexington, Medina, and Cedar Grove were some of the areas that got 4-6" of snow when 3" was expected at most, but the atmosphere had other plans. Because we got a significant amount of sleet this morning, that made it easier for the snow to start sticking immediately upon falling. Our other factor was the snowfall rates which were high enough to cause totals to increase very rapidly.



Ultimately, this winter storm is finally starting to come to an end with snow and ice totals in northwest Tennessee as high as 8" and as little as just a trace in southwest Tennessee. A few snow showers just recently tapered off along the Tennessee River. We'll start the melting process tomorrow but this snow and ice may stick around some areas for several days.

TONIGHT
Black ice is the main concern for us overnight and it's expected to be a problem for virtually all of West Tennessee. Temperatures will get well into the teens at the coldest point of the night and wind chills will be in the single digits early Saturday with winds still out of the north at 10 to 20 miles per hour.
Skies will become clearer tomorrow with sunshine getting the melting process going but I believe we'll have black ice on Sunday morning too. Shaded areas will hardly see any melting at all because high temperatures will only be in the upper 20s and lower 30s. Be very careful if you have to drive in the area tomorrow!

Stay with WBBJ 7 Eyewitness News for the latest forecast and keep up with Storm Team Weather online too for more updates.

Winter Storm Watch from Midnight (12 a.m. Friday) to 6 p.m. Friday

NOTE: This blog post is pertaining to a chance for snow and ice that is forecast 

to occur between tonight, Thursday, January 11th, 2018 and Friday, January 12th, 2018.

Over the next 24-36 hours, West Tennessee will see rain transition to freezing rain, then sleet, and finally snow. This will be the first significant impact we'll face this winter season, so it's important that we get prepared today!

SET-UP
Below, is a chart showing the different pressure systems and fronts in the United States as of this morning. Our storm is the "L" in western Oklahoma, and it's attached to a long cold front extending from Mexico to Canada. Both of these features will be in the Mid-South by tonight and will continue to be key players in the forecast throughout the day tomorrow.

Here's an idea for where that low pressure system will go over the next few days. We'll be on the northwest side of the low pressure system Friday morning. That, typically, is where you see the higher snowfall amounts accumulate, but the cold air from the Northern Plains will need to catch up to it quickly enough to cause a change over to snow.



FORECAST
The general trend in the latest model data this morning (Thursday, January 11th 8:00 a.m.) is that we'll be dealing with rain showers (some heavy) off and on throughout the day today into the evening. Between 3 p.m. Thursday afternoon, and 3 a.m. Friday morning, West Tennessee will have some scattered thunderstorms in the Mid-South, but because we won't have a lot of energy in the atmosphere, severe weather remains unlikely.

West Tennessee generally just has a chance for a few thunderstorms and strong thunderstorms are not likely. However, because of how muggy it is out there, I do expect some pockets of heavy rain to take place this afternoon, evening, and overnight.

After the cold front starts to move in, we'll change to ice. The animation below (midnight tonight through 9 p.m. Friday) shows that changeover happening in Jackson between 3 a.m. and 6 a.m. Friday. The green color on the map below represents rain, while the reddish and purple colors represent ice, and blue is snow.

The freezing rain and sleet will not be constant Friday morning but could be heavy at times in West Tennessee. Where exactly depends on the path of the storm but I suspect our viewing area will be ground zero for some of the highest ice accumulations. That said, this still doesn't appear to be a major winter storm for the Mid-South. The map below shows only a 30-40% chance for a quarter of an inch of ice to accumulate on Friday in the dark green area.

The trend between yesterday afternoon and this morning also points to lower snowfall totals, but there are still some models putting out high amounts. Again, this all hinges on how quickly the cold air reaches us! Just take a look at this one particular model, the North American Model, and see the differences in output as it's refreshed 5 times since yesterday.

 

Both in placement, and amounts, this model has not been consistent with where we will get accumulating snow. However, looking at the data from different models as a whole, it still looks like Martin, Huntingdon, Paris, and Camden stand the best chance for the higher totals. The map below shows a 40-50% chance for 2" of snow in the blue area over Weakley, Henry, and Benton counties where the rest of West Tennessee is only looking at a 20-40% chance for that occurring.

After transitioning to snow Friday afternoon, we'll finish all forms of precipitation by Friday evening. At this point, I think we're certainly looking at a coating to 2" of snow on grassy surfaces in West Tennessee by the end of the day on Friday. There could be isolated totals of 2"-3" in northwest Tennessee as well, especially for those living near the Tennessee River.

For Jackson, I'm expecting a coating to 2". This graph shows most of this particular family of weather models giving us a minimum of no snow at all to 3-4" but I think that range is an outlier for us right now. The black line represents the model average showing 0.5" of snow.

FINAL DETAILS
I try not to predict unpredictable human behavior, but I'm thinking administrators will issue school closures for tomorrow.

It's worth mentioning that overall, whatever falls from the sky on Friday, will eventually be met with very windy conditions. That means a wind chill at or below 15°F all day long. When those windy conditions with gusts up to 40 miles per hour meet up with ice-laden tree branches, I think we'll have power outages - spotty not widespread. We'll have some sunshine this weekend but below freezing temperatures this weekend with partly to mostly cloudy skies will limit melting over the weekend too.


Summary

• Rain changes to ice overnight tonight falling by 6 a.m. at the latest for most of West Tennessee. Despite the sharp drop in temperature, severe weather isn't expected overnight but we'll have some thunderstorms.
• Freezing rain and sleet will be scattered Friday morning before changing to snow Friday afternoon.
• A coating to 0.25" of freezing rain on tree branches and power lines
• A coating to 2" of snow is expected with isolated totals of 2"-3" in northwest Tennessee near the Tennessee River are possible (mainly in Weakley, Henry, Benton, and Carroll counties)
• Friday will be cold and very windy with spotty power outages likely

We'll be updating our snow and ice totals forecast before MidDay and Noon with Meteorologist Moe Shamell, adjusting the timeline for the onset snow and ice, as well as revising the various impacts. Tune in to WBBJ 7 Eyewitness News for the latest forecast!