It was certainly an active afternoon and evening last night as multiple rounds of showers and thunderstorms moved through the region. Although we experienced some pretty loud thunderstorms, our severe weather never materialized. However, for other areas across the Great Lakes and Plains multiple instances of severe weather reported. The strongest of which occurred in Southwestern Michigan as multiple strong tornadoes impacted multiple communities yesterday afternoon.
As this system continues to pass to our east today we'll see temperatures drop across the region as a cold front passes through this morning. At 5:15 am we're currently sitting in the upper 50's with the cooldown expected to begin soon, but through the morning we should achieve our high temperature in the mid 50's as this front approaches. As this front moves in a few isolated showers will still be possible, however the biggest impact we'll feel from this front will be gusty winds behind it along with temperatures gradually dropping through the afternoon.
As winds pickup today they will be orientated out of the northwest keeping some chill in the air. Into the evening though winds will gradually shift out of the southwest which will continue through the next two days. This will quickly warm us up back into the 60's tomorrow and possibly even make a run at 70° Monday!
1:45AM: Steady showers continue to push across the Stateline, but wind gusts have come down a bit. A few spots may only see the gusty showers produce winds only up to 40 mph, remaining below severe limits.
12:40AM: Though it may not look all that impressive, the showers in Northwestern Illinois have been able to tap into stronger winds above the surface, producing wind gusts of 40-50 mph in some spots. While not severe, gusty winds may accompany the showers and storms overnight.
11:15PM RADAR: The two areas of storms are moving into Southern Wisconsin and Western Illinois respectively tonight, producing heavy rain and frequent lightning. Storms are sub-severe right now. Strongest storms may be able to produce a few strong gusts (up to 50 mph) from time to time as they move to the Northeast at around 50-60 mph. ETA for Southern storms to reach Rockford at current pace: about 1-1:30AM.
9:30PM UPDATE: We are watching two main areas of storms late this evening. The first in Iowa should push North of us into Central Wisconsin overnight. The 2nd round in Northern Missouri will move our way, likely after 12AM now. The later timeline of storms will aid in a weakening trend, limiting the potential severe risk locally. While we are not fully out of the woods, the chance for a severe storm with 60+ mph winds is diminishing. Showers will linger into the morning, but we will dry out by mid-day with temperatures falling to the 40s by the afternoon.
6:30PM RADAR: All remains mostly quiet across the Stateline, but the next window of storms is beginning to take shape across Missouri and Iowa. In the wake of the storms Friday morning, the atmosphere is a little more stable locally. This has kept us drier, while the main axis of storms develops South and East of us. Now through 10PM will continue the lull in precipitation, with only a small chance for an isolated storm.
An isolated cell may try to bubble up locally before 10PM, but the main window arrives between 10PM-2AM. Damaging winds and heavy rain will be the main threats, but a brief spin-up tornado could be possible as well.
The cluster or broken line of storms will enter Northwestern Illinois after 10-11PM, then center themselves along the I-39 corridor near or after 12AM. By 2-3AM, the strongest of the activity will have pushed off to the East, but steady showers or a few rumbles of thunder remain possible through 2-3AM. Be sure to have a way to receive warnings and make sure those warnings will wake you up since the storms will be coming in late tonight!
The severe weather outlook saw little to no change overnight as the Storm Prediction Center maintained a level 2 of 5 Slight Risk for the area.
Timing Out the Storms:
Now, today's severe threat is broken into three distinct periods: a morning threat, a possible afternoon threat, and then an overnight threat.
Morning (6AM-10AM: This will include a batch of widespread rain and isolated non-severe storms. If any storm were to become severe, it would be for hail as these will be elevated in nature.
Afternoon (12PM-6PM): There will be a few lingering storms behind the stuff that passes through during the morning. However, we have a warm front hovering around northern Illinois, northern Indiana, and southwestern Michigan. Any storm that interacts with this warm front will quickly go severe, posing a threat for all severe hazards. The odds of that are low but still something to monitor.
Overnight (9PM-6AM):
Thunderstorms developing along the cold front will move into the Stateline closer to the midnight hour, with chances lingering into early Saturday. These will primarily pose a damaging wind threat, but with plenty of spin in the atmosphere still in place, an isolated tornado or two cannot be ruled out. Again, be sure to have many ways to receive severe watches and warnings from start to finish today.
For a third straight morning, parts of northern Illinois and southern Wisconsin are waking up under a Dense Fog Advisory. This is for Winnebago, Boone, Ogle, Lee, DeKalb, and McHenry County in northern Illinois as well as Green, Rock, and Walworth County in southern Wisconsin. We'll see if the National Weather Service expands this further to include our western areas but for the time being, this advisory will run until 10AM this morning
As of 3:30AM, visibility has rapidly dropped to a half mile or less for most locales. Lowest values are up near the Monroe area with .3 mile visibility.
Dense Fog Safety Tips:
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.
Friday could bring the season's first severe weather risk for much of the Stateline. There are three distinct windows for potential storm development, each with varying threats and coverage.
MORNING: The first window is centered around the morning, with widespread rain and a few embedded storms. Since these storms will be elevated, severe risk will be minimal with a main threat of small hail and heavy rain.
AFTERNOON: The afternoon is a bit more of a conditional risk. If storms develop, the environment will be primed for strong to severe development with all hazards possible. The main threats will be large hail and damaging winds. A brief tornado is also possible if a storm can attach itself to a passing warm front, enhancing the potential rotation. Storm coverage will be isolated in nature, meaning there will be many dry hours and dry locations at any given time.
EVENING/NIGHT: An approaching cold front will bring a renewed chance for showers and a few storms, with some gusty storms possible. The loss of daytime heating will weaken storms a bit, but a few strong gusts may be possible with some pockets of heavy rain.
The highest chance for storms will be in the morning, but the strongest storms will likely be in the afternoon or early evening. Main concerns throughout the day will be winds and hail, but the afternoon may pose a brief tornado risk as well. Any showers and storms will clear by mid-morning Saturday behind the passing cold front.
The entire Stateline is now under a Slight (Level 2/5) Risk for severe weather from the Storm Prediction Center. The highest risks locally are for hail and wind, while the tornado and flooding threats are a little on the lower side. Storms may be possible throughout the day, but the strongest storms — should they develop — will be centered around the afternoon and early evening. Continue to follow for updates through Friday!
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.
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 sizeof 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.
