We've all grown used to the three categories for severe weather outlooks by the Storm Prediction Center. These outlooks included Slight, Moderate, and High. Of course, we've all joked before that Slight risk doesn't really mean slight. In the weather business, a slight risk usually keeps you fairly busy. On many occasions it is later followed with either a tornado or thunderstorm watch. The Storm Prediction Center in Norman, OK has been studying for years how to better communicate severe weather information to the public.
Back in the early days, the slight, moderate, and high risk information was only communicated to weather service offices, media outlets, and emergency managers. However, in the days of instant communication everyone has access to severe weather outlooks. For the non-weather junkie, the three categories can be a little confusing.
Here's an example of the old way.
This is an example of the same day using the new severe weather outlooks.
You have probably noticed there are two more categories now added. This includes the Marginal and the Enhanced. The Marginal is lower risk of severe weather than Slight and the Enhanced is a higher risk than Slight.
The SPC will use the following criteria when assigning the new outlook categories.
Day 1: a. General Thunderstorms - 10% or greater probability of non-severe or near severe thunderstorms. b. Severe Category 1 - Marginal - 2% or greater tornado probability, or - 5% or greater severe hail or severe wind probability. c. Severe Category 2 - Slight - 5% or greater tornado probability, or - 15% or greater severe hail or severe wind probability. d. Severe Category 3 - Enhanced - 10% or greater tornado probability, or - 30% or greater severe hail or severe wind probability. e. Severe Category 4 - Moderate - 15% or greater tornado probability AND 10% or greater probability of an EF2+ tornado, or - 30% or greater tornado probability, or - 45% or greater severe wind probability AND 10% or greater probability of a wind gusts 75 mph or greater, or - 45% or greater severe hail probability AND 10% or greater probability of hail 2 inches or greater in diameter, or - 60% or greater severe wind probability, or - 60% or greater severe hail probability. f. Severe Category 5 - High - 30% or greater tornado probability AND 10% or greater probability of an EF2+ tornado, or - 45% or greater tornado probability, or - 60% or greater severe wind probability AND a 10% or greater probability of a wind gust 75 mph or greater.
In turn, you will see a lot more marginal severe weather outlooks here in the Southeast replacing what used to be labeled as a Slight Risk. You might wonder what the new outlook would have looked like had the SPC used it on April 27th, 2011.
We're beginning to see development of discrete, widely scattered thunderstorms back over east central Mississippi as the atmosphere grows increasingly unstable. Of particular interest is this intensifying thunderstorm to the southwest of Philadelphia, Mississippi. Lightning has been increasing with this storm, as well as signs that it already has a rotating updraft in the mid-levels.
We will need to monitor storms like this very carefully over the next few hours as they will have the potential to become supercells with the risk of a few tornadoes. A Tornado Watch is already in place for most of Mississippi until 9:00 pm. Interestingly, the text of the tornado watch mentions that a few longer-lived supercells with the potential of a couple of strong/intense/damaging tornadoes will be possible.
J.P. Dice has just stepped into the office, and Wes Wyatt will be in soon for a full staff to watch this situation. We will have updates through the rest of the day both on air and online. Stay with FOX6 for complete severe weather coverage.
FOX6 WBRC Weather
Blog Severe Weather Analyst
We're watching the line of storms off to the west very carefully. Regional radar data this morning shows it already approaching the Mississippi River just before 11:30 am. The latest data from our high-resolution models are also keying in on this and have the line approaching our area a little earlier this evening than maybe the last data set or two has shown.
By 5:00 pm, or possibly a little before, we may see a few individual strong thunderstorms develop over parts of the area. This will especially be the case over portions of western and central Alabama... generally along and west of I-65. A few of these could possibly become severe, and these individual thunderstorms would be what we would have to watch most carefully for the risk of a few tornadoes.
By 8:00 pm, the RPM model has the main line of thunderstorms approaching the Alabama state line from the west. We will still have to watch for a few lone supercell thunderstorms out ahead of it though. With the line itself, the potential for damaging winds... possibly as high as 60 to 75 mph... will increase, but there still may be a couple of spin-up tornadoes with bowing segments and embedded supercell-like structures near breaks in the line.
By 11:00 pm, our high resolution model has the main line moving into places like Double Springs, Jasper, Tuscaloosa, and Eutaw. With this line, we will continue to see the risk of damaging straight-line winds in excess of 60-70 mph and the potential for a few spin-up tornadoes. Out ahead of this, we will still need to monitor the situation carefully for the risk of a few individual storms continuing ahead of the main line, with the risk for a few tornadoes.
We will continue to monitor the situation, and we will have updates on air and online through the day as needed.
Fred Gossage with Mickey Ferguson
FOX6 WBRC Weather
THIS AFTERNOON: Watching the radar today - we'll continue to see some spotty showers and thunderstorms develop. The best chances for rain again today will be areas north of I-20. While we could see rain develop anywhere in our viewing area, the most organized and stronger storms will develop near a front we've been watching all week. We can expect highs this afternoon to reach the mid 80s with temperatures tonight falling into the upper 60s.
WATCHING SEVERE THREAT: Our focus is on a deep trough that will result in some severe weather across the Southeast tomorrow. For us, the biggest threat will come after 8pm Monday. The Storm Prediction Center has the state in a Slight Risk for severe storms. The main threat will be west of I-65 and including damaging straight-line winds. Power outages and damage is likely with this system. While it's possible we could see an isolated tornado, severe weather parameters really continue to point to a more linear system. Tornadoes that do develop would likely be the small and quick spin-up. Storms could linger into early Tuesday morning. Forecast models continue to slow this system down which isn't a bad thing. It means a little less instability or energy for the storms to develop.
Tomorrow's forecast looks warms with partly sunny skies and highs in the lower to mid 80s. We'll see lingering showers though Tuesday morning and even a few thunderstorms early Tuesday. After that, expect much cooler and drier weather through the week and weekend. The weather is looking perfect for the races at Talladega next weekend.
Stay with Fox6 for any changes in the forecast and remain weather aware especially tomorrow night.
Fox6 Chief Meteorologist
Enjoy the warm weather while it is here. Another big change is on the way and this time it includes some strong thunderstorms followed by some chilly air. Models differ a little on the timing of the front, but I'm confident to say we'll be feeling the cooler air by Friday night. The question is what time does the rain and thunderstorms arrive? The system could be a severe weather maker just to our west for parts of Arkansas, Louisiana, and Missouri. Models continue to show a well-defined line of storms Thursday ahead of the front. The line seems to loose much of its definition as it arrives into Alabama turning into thunderstorms and widespread rain.
The graphic below shows the Significant Tornado Parameter based on the NAM for late Thursday morning. You can clearly see the highest risk for severe storms across Eastern Oklahoma and Kansas at that time. The threat will continue to move to the east through the day losing much of the wind shear as it gets closer to Alabama.
By late Thursday night most of the line of thunderstorms is still expected to be west of Alabama. Right now, the greatest risk for strong to severe storms appears to be areas west of I-65 as the system moves in early Friday morning. This will likely be an overnight event so I encourage everyone to make sure their NOAA weather radio is working and set properly.
The main risk with this system will be isolated gusty straight-line winds. We could have winds in excess of 50mph in a few places. The system is expected to turn into more of a rain event early Friday during the morning commute. We're watching the system closely, but see no reason to believe tornadoes will be a threat across Alabama. The NAM is indicating widespread rain on Friday morning.
By Friday afternoon and evening, most of the rain will have pushed to the east making for pleasant conditions for high school football games. It's possible we could have a few lingering showers during the early evening for portions of East Alabama. The graphic below shows the forecast position of rain during the early afternoon Friday.
Overall, the rain chances later in the day Friday should decrease quite a bit. Expect the winds to increase out of the Northwest with cooler temperatures. In fact, temperatures Friday evening will quickly fall into the upper 50s with overnight lows in the 40s.
You'll feel the effects of the front when you wake up Saturday. Temperatures in some places will be in the mid 40s with highs in the 70s. Mostly sunny skies will remain in the weekend forecast as cool air and high pressure build behind the system.
I'll have more details on Fox6 News later this evening.
Fox6 Chief Meteorologist
Slight Risk For Severe Storms Including Tornadoes, Damaging Winds, Hail and Flash Flooding!
SIMULATED RADAR IMAGES BETWEEN 2-4PM:
Followers in the states under the gun for later today need to pay close attention to the weather and have a way to get weather warnings. Timing is poor seeing kids will be getting out of school and people will be getting out of work during the height of the bad weather. While on the road, best thing to do is to have the radio on and listening for traffic and storm updates.
Jill Gilardi Fox 6 Meteorologist
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