Severe Weather Preparedness: Severe Risk Categories

Severe Risk Categories:  

The Storm Prediction Center in Normal, OK uses a five-category system to clearly communicate the overall severe weather threat, ranging from a Level 1, Marginal Risk to a Level 5, High Risk. 

These represent the expected intensity as well as how widespread the impacts may become. 

Marginal Risk (Green): Isolated severe storms are possible. Widespread severe weather is unlikely. 

Slight Risk (Yellow): Scattered severe storms are possible. Storms will be a tad bit more organized and may produce all severe hazards. 

Enhanced Risk (Orange): Numerous severe storms are expected with a greater concentration of damaging winds, large hail, and a few tornadoes. More of a substantial threat. 

Moderate Risk (Red): Typically reserved for significant severe weather outbreaks. This includes the potential strong tornadoes (EF-3+), widespread damaging winds, or very large hail. Storms in nature will be more intense and long-lived. 

High Risk (Pink): A level 5 high risk is rare but we've seen a few of them in previous years. In fact, part of the Quad Cities viewing area was under a high risk back in March 2023. This includes the potential for long-track,violent tornadoes as well as widespread destructive winds. 

Severe Weather Preparedness: Hail and Wind Safety

Hail & Wind Safety: 

While tornadoes often grab the headlines, storms that produce destructive winds and large hail can be just as dangerous - making it equally important to take safety precautions for all threats. 

 

  

Severe Storm Categories: 

In recent years, the National Weather Service uses a three tier platform to communicate the potential damage from severe thunderstorms:

Base: Standard - hail at least one inch in diameter and or wind gusts of 58 mph or higher. 

Considerable: Elevated - hail up to 1.75" in diameter and or wind gusts up to 70 mph. 

Destructive: Dangerous - often issued when a storm is producing hail up to baseball size and or wind gusts are over 80 mph. Like a tornado warning, a severe thunderstorm warning with the "destructive" tag will trigger a Wireless Emergency Alert on your phone. Take immediate action. 

What Dictates Hail Size: 

Hailstones come in a wide range of sizes, from as small as a pea to as large as grapefruits. Recently, there have been a few storms that were warned for DVD-sized hail (5.5"). Now, the size of the hailstone is dictated by how long the stone can remain suspended within the thunderstorms updraft (rising air into the thunderstorm). Stronger updrafts can keep hailstones aloft longer, allowing them to gather additional layers of ice.  

When severe storms threaten with destructive winds or large hail, staying safe starts with seeking study shelter well before the worst arrives. 

Move indoors, ideally to a basement or an interior room away from windows. If you are outside driving, find a safe place to pull over and get indoors. Vehicles offer limited protection and can be severely damaged by large hailstones and wind-debris. 

Northern Illinois wakes to yet another dense fog advisory

Dense Fog Advisory:

For the second straight morning, northern Illinois and southern Wisconsin are waking up under a DENSE FOG ADVISORY. Unlike yesterday, however, the fog will be more stubborn to dissipate as the advisory is scheduled to last into midday. 

  

Dense Fog Safety Tips: 

Visibility has rapidly dropped to a half mile or less in most locales. If traveling, slow down and increase your following distance from other vehicles to increase reaction time. Use low-beam headlights or fog lights - never high beams as that can reflect off the fog, further reducing visibility.  

Near record warmth Friday as severe storms threaten northern Illinois

 

Temperatures are expected to climb Friday as a strong warm front surges north across Illinois Friday afternoon. Highs during the afternoon are likely to warm into the 60s, possibly reaching 70 degrees (depending on how long clouds and rain last from the morning). 70 is the record high for Rockford which was set in 2000. But the warmth will also come a chance for a couple rounds of thunderstorms, first during the beginning of the day and then again late in the evening.

The first wave will arrive ahead of the warm front and likely remain elevated. What are elevated thunderstorms? They are storms that develop over a stable air mass at the surface. The instability is aloft, rather than near the surface. While these don't pose a high severe risk, elevated storms can produce hail and even some gusty winds. Storms from late Thursday night will move from the Plains into northern Illinois Friday morning. These storms will be moving in ahead of the arrival of the warm front, so the risk for anything severe remains low. The only thing we would need to keep an eye on would be if the front speeds up a little as the storms move out. If that occurs, then there is a chance that a storm or two could become surface based and that would slightly increase the chance for an isolated severe storm. The risk of that happening does remain low, but it is something we'll be keeping an eye on.

The next chance for thunderstorms will arrive Friday night with the main cold front. While the timing isn't overly favorable for severe weather locally plenty of warmth, moisture, and strong winds could lead to a few bursts of stronger wind gusts. This window would occur from roughly 10pm/11pm, to just before 3am/4am.

The Stateline is highlighted under a 'slight risk' for scattered severe storms, with the second wave posing the best chance, but we also have to watch what comes in mid to late morning/early afternoon. In between, temperatures will warm and it may even feel a little muggy for a time through the late afternoon and evening.

Be sure to remain aware of the weather for Friday and be sure to follow the First Warn Weather Team for weather updates!

Fog and drizzle expected to move back in Wednesday evening

 

Wednesday started off with dense fog and it looks like we'll end the day with fog, and drizzle. A warm frontal boundary positioned across central and southern Illinois will slowly march north through the evening and overnight. This will be in response to a weak surface low pressure system that'll move northeast of St. Louis tonight, into northwest Indiana Thursday morning.

The Stateline will remain north of both the low and warm front tonight but the increase in moisture associated with both features will cause an increase in drizzle and light rain showers, along with fog.

The fog could become dense through the late evening and overnight, leading to once again some impacts to the morning commute Thursday. The fog and drizzle may linger for some areas, especially east of I-39, through early afternoon before we likely see a redevelopment of fog Thursday evening and overnight.  

Thick fog prompts advisory for all of northern Illinois

Dense Fog Advisory:

A Dense Fog Advisory has been expanded to include the entire region with the exception of Green County, and will remain in place until 9AM. 

 

  

Visibility is expected to drop to a quarter mile or less, creating hazardous travel conditions for the morning commute. If traveling, make sure to travel at slower speeds, use low-beam headlights, and allow extra time to reach your destination. 

 

 

Overnight Rain Chances:

Once the fog lets up, mostly cloudy skies will remain for the rest of our Wednesday. A shift to a more southeasterly wind will give temperatures a slight boost, placing them near the 50° mark.  

While a few sprinkles and showers will be possible late this afternoon into the evening, a better chance arrives overnight into the first half of Thursday as a weak storm system and it's warm front pushes to our south. Some instability will be present, allowing a few embedded thunderstorms to be possible. Severe weather is unlikely.

 

Severe Weather Preparedness: Lightning Safety

Types of Lightning:

Lightning, a sudden, intense discharge of electricity that occurs during a thunderstorm. Though lightning only lasts fractions of a second, it has a wide-variety of effects include atmospheric chemistry, ignites wildfires, and poses hazards to people.  

Believe it or not, lightning occurs in several different forms, each produced by a variation of interactions within a thunderstorm. The most common, cloud-to-ground (CG) lightning where the electrical charge travels between the storm cloud to the Earth's surface. 

Other types of lightning include: 

1. Intra-cloud (IC): Very common.

2. Cloud-to-cloud (CC): Uncommon.

3. Cloud-to-air (CA): Occasional. 

4. Ground-to cloud (GC): Rare. 

Lightning Safety:

Similar to tornado safety, lightning safety is critically important because lightning is a natural hazard that can strike miles away from a storm. Many lightning-related injuries occur not because storms are directly overhead, but because people underestimate the threat or delay seeking shelter. Remember, when thunder roars, GO INDOORS! Once you've taken shelter, it is essential that you wait 30 minutes after you last hear thunder to resume activities.