Breaking down Monday's threat for severe weather

 Monday will continue the streak of active weather this April with yet another threat for severe storms. This potential has a very high ceiling with potent severe weather possible, but is very conditional. A round of storms will develop Sunday night across the Southern plains and work toward the Ohio River valley Monday morning. The placement and evolution of these storms is very important to see how the afternoon storm environment will look.

There is a chance the morning storms work to lay down an outflow boundary and wipe out the environment for the afternoon. If the early day round of storms fizzles out or moves through quicker, the afternoon window could be more potent for storms. The highest confidence on a severe weather risk will remain primarily South of I-80 in Central Illinois with a better chance to see the environment recover following any morning storms. Conversely, there is less confidence that far Northern Illinois will have enough time to recover following any morning activity. There is still a potentially high end severe risk locally, but it hinges greatly on how quickly morning storms are able to clear out.

We will have two rounds of storm activity locally in the Stateline. One round early in the day and another late afternoon-evening round. 8AM through 3PM will bring scattered, but largely non-severe storms. Heavy rain and small hail may still be possible, but the severe threat will be low with this wave. Late afternoon into evening will bring a higher risk for strong to severe storms, but as mentioned above, hinges on how quickly the morning round clears out. Severe storms will be most likely between 3-8PM locally, with some scattered storms remaining through 10PM-12AM but quickly decreasing severe threat during that time.

IF all comes together with the morning round clearing and atmosphere recovering for the afternoon window, all hazards of severe weather may be possible -- including some tornadoes. Storms will initially develop in discrete supercell structures with a higher threat for tornadoes and large hail. But quickly those storms will merge into a line or cluster, enhancing the wind threat. Embedded tornadoes will remain possible during this time as well.

This is one of those potentially higher-end scenarios that also has high uncertainty. It will depend very heavily on how the storms to the West evolve overnight and where outflows are laid by early morning. If all falls into place, a widespread severe weather outbreak is possible. But if morning storms wash out the environment, we would be limited to a weaker evening round. Monday morning should bring some much-needed confidence to the forecast. That said, remain weather aware Monday afternoon and make those severe weather plans now in case any warnings are issued. We will be sure to keep you updated!

Increasing threat for widespread severe weather Monday in Northern Illinois

 A broad region may see a potential for severe weather on Monday, including Northern Illinois. The Storm Prediction Center has been on this threat all week, highlighting the severe weather potential since Thursday. The latest outlook as of Saturday night shows a Level 3/5 Enhanced risk for severe weather stretching from far Southwestern Wisconsin down into Northern Arkansas. For a large majority of this area, all hazards of severe weather will be possible, including a threat for tornadoes.

But there are still a number of things that need to fall into place before this severe threat develops. Seeing as we are still nearly 48 hours from the severe threat, there are some uncertainties as to how the environment will evolve. Multiple waves of storms look possible, including a morning round. But how fast that round clears will determine how much the atmosphere is able to recover before the afternoon and evening. Another thing that will impact severe potential is storm mode. If we see discrete supercells, tornado and hail potential will be higher. If storms merge into a line or cluster quickly, the wind threat would be highest with some embedded tornadoes.

Our primary severe weather timing will be from about 3-8PM, but some of the morning and afternoon storms may pose a lower risk for severe weather too. One thing is for sure, Monday looks to be another active day in Illinois with regard to severe weather. Sunday will be the days to make the severe weather plans of what you will do in case a warning is issued. Think of where you might be between 3-8PM and where you will go if you receive a warning. Be sure to stay updated on the forecast through Monday as we continue to bring you the latest!

Pleasant but cooler weekend with patchy fog possible overnight

 This weekend will be a pleasant one even if we don't quite see the 80s like we saw Thursday! Temperatures will remain above average with highs in the upper 60s and lows in the 40s.

With a bit of lingering moisture and a lighter wind, we could see some patches to areas of fog develop Friday night. Highest confidence on fog coverage would be focused along and East of I-39, but patchy fog may be possible area-wide.

Aside from that patchy fog, the weekend is uneventful and pleasant with high temperatures pushing into the upper 60s or right around 70! Both Saturday and Sunday will feature fair amounts of sunshine, leading to pleasant conditions for outdoor activities!

Monday will bring our next chance for some storms, with some potentially severe. There are still a number of things to hash out before we get there to determine timing and exact level of severe threats, but a broad region of low pressure will bring a large area of storm potential stretching from Southern Wisconsin down into Arkansas. The main questions remain with how much recovery we see after a morning round of storms, and where the placement of the most favorable environment will be. But as of now, all hazards of severe weather may be possible including tornadoes. Stay tuned for forecast updates through the weekend!

Quiet weekend ahead, then eyes on Monday’s storm potential

Cooler Friday: 

Sunshine did most of the heavy lifting Thursday, but a steady south to southwest breeze helped seal the deal. That warm, dry flow allowed temperatures to climb efficiently through the afternoon, pushing Rockford into the 80s for the 4th time this year. 

  

Temperatures won't be quite as warm moving forward as our next cold front pushes through before the midday hours. Ahead of this cold front will also be a few showers and possibly a thunderstorm or two. Chances will come to an end rather quickly, allowing clearing to gradually take place. Afternoon highs will end up roughly 10 to 12 degree cooler than Thursday, landing near the 70 degree mark. 

  

Weekend Forecast:

Looking ahead to the weekend, things shape up to be fairly quiet. Expect mainly dry conditions both days with temperatures hovering around 70 degrees. Rain chances should hold off as they will be more focused across the southern plains. Our next opportunity for rain and thunderstorms won't arrive until late Sunday night with chances stretching into Monday.  

Monday's Severe Potential:

It's this precipitation that we'll need to keep a close eye on as it may play a role in determining Monday's potential for strong to severe storms. How morning showers and storms evolve could either limit or enhance our local threat. At this point, the primary focus for stronger to severe weather sits farther south along the warm front in central and western Illinois. Severe potential will also be heightened near the surface low ax it lifts into eastern Iowa. For that, the Storm prediction Center has expanded the 30% or enhanced risk equivalent to included a majority of the Stateline. Again, something to keep an eye on over the weekend. 
 

Looking ahead to next chance for widespread storms Monday

 While Thursday night's severe weather event seems relatively isolated in nature, we could be looking at a more widespread chance for storms Monday. There are several things that forecasters look at to identify potential for severe weather. The primary ingredients include moisture, instability, lift, and wind shear.

Two ingredients will be met with a "shortwave" in the jet stream that looks to push overhead toward Monday. This will provide the lift along a surface low pressure system and the necessary wind shear to keep storms going. Broader forcing and ideal timing of storms arriving in the day will allow for a more widespread storm potential compared to Thursday night's storm potential.

The other two ingredients are related to moisture. Abundant gulf moisture will approach the area Monday, tugged Northward along that shortwave. That will allow for more widespread rain with also some heavier rain possible. Right now, the most aggressive instability, or storm energy, looks to be centered across Central Illinois. But the Northern fringes may produce severe weather locally as well. There are still several factors that will need to fall into place before this severe threat would come to fruition.

While we are still a few days out, the Storm Prediction Center has already highlighted a broad region for severe weather potential, extending up to far Southern Wisconsin with the 15% risk, which is equivalent to a Level 2/5 Slight risk when it comes to severe weather probabilities. A 30% risk extends across Southern Illinois into Missouri and areas South. That is equivalent to a Level 3/5 Enhanced risk. While we are still more than a few days out, Monday will need to be a day to watch for widespread storms and potential for severe weather!

Thunderstorms chances increase late Thursday evening, Isolated severe threat overnight

10:20PM UPDATE: A Severe Thunderstorm Warning has been issued until 11pm for far northwest Jo Daviess County. 60 mph wind gusts and penny sized hail will be possible. The storm is currently moving northeast at 50 mph.

 

ORIGINAL POST: Temperatures Thursday afternoon warmed into the upper 70s and lows across northern Illinois and southern Wisconsin, with Rockford's high reaching 81 degrees. Skies have been dry throughout the afternoon as a few showers and isolated thunderstorms have bubbled up west of the Mississippi River, and into southwest Wisconsin.

Most of the evening will feature dry skies but an isolated shower/storm can't entirely be ruled out after sunset across far northwest Illinois. The main line of storms will arrive with the cold front, set to move in overnight. The Storm Prediction Center continues to highlight southern Wisconsin and northern Illinois under a 'marginal risk' for an isolated severe storm or two tonight.

Ongoing severe weather can be seen with a line of storms stretching from southern Minnesota, down through Iowa, and into Kansas. This is where the highest risk for severe storms will be through the evening. As the line shifts east tonight, it should generally be on a weakening trend as it nears the Mississippi River. However, there could still be just enough instability to help maintain at least an isolated severe risk - mainly with strong wind gusts - through the early overnight.

It looks like the storms should be entering into northwest Illinois between 10pm and Midnight, moving east through 4am. Frequent lightning and heavy rainfall will also accompany any of the storms that move through, but thankfully our flooding threat is low. We'll continue to monitor the radar out west and as the storms approach the region later tonight. 

Warm, breezy & June‑like with storm chances to follow

Next Severe Potential:

After the active week we dealt with last week, things have been noticeably quieter. That lull won't last completely, though - a few strong storms could roll through northern Illinois late this evening into the early stages of Friday morning. The Storm Prediction Center has maintained the level 1 of 5 Marginal Risk for severe weather for the entire area, with gusty winds being the primary concern.  

Ahead of tonight's thunderstorm chances, a June-like afternoon is shaping up thanks to very dry, but breezy conditions. Winds will be out of the south-southwest, gusting up to 30 mph at times. This will help push temperatures back into the low 80s, marking Rockford's 4th 80-degree day of the year. Normally, average highs towards the final stretch of April are sitting in the low to mid 60s. 
 

Severe Potential Shifts South:

Beyond today, the focus for any severe weather shifts well to our south. Storms capable of producing strong winds and large hail will be possible across Texas, Arkansas, Louisiana, and Mississippi. 

 

  

Heading into the weekend, we'll be watching a classic dryline set up take shape over the southern plains. That isn't a term we typically use this far north when talking about severe weather. A dryline is a boundary where warm, humid air meets dry, hot air. IF a storm were to form along the dryline, supercells capable of producing all severe hazards, including strong tornadoes, will be possible.  

Monday is the day we'll need to keep a closer eye on for strong to severe storms. The Storm Prediction Center has placed the entire Stateline area under a 15% risk, which is equivalent to a level 2 of 5 Slight Risk. A higher 30% risk, or Enhanced Risk (level 3 of 5), is centered further south across eastern Missouri and southwestern Illinois.