Some across northern Illinois and southern Wisconsin woke up to a little frost Thursday morning before clouds rolled in shortly after sunrise. Temperatures dropped into the low 30s where skies were clear a little longer through the night, allowing some of the frost to develop. Where clouds moved in a little earlier, temperatures didn't fall quite as much.
A Frost Advisory will go into effect for southern Wisconsin, including the counties of Green, Rock, and Walworth beginning at Midnight and lasting until 8am Friday. Skies will once again turn partly cloudy overnight allowing temperatures to drop into the low to mid 30s.
Cloud cover will increase during the morning and afternoon as yet another weak low-pressure system moves across northern Illinois, allowing scattered showers to develop during the afternoon and early evening. High temperatures on Friday will warm into the mid 50s.
April has delivered no shortage of rain across the northern Illinois area. So far, Rockford has picked up 6.23" inches of rain, keeping the ground soaked and waterways high. And it doesn't look like Mother Nature is finished just yet, with another rain chance lining up before we turn the page to May.
Today's rain will be very similar to the chances we've seen this week, with showers staying scattered and generally light. Because of that, most Stateline locales will only pick up a few hundredths of an inch, with totals staying below a tenth of an inch. Conditions will dry out this evening into tonight, allowing low temperatures to fall into the low 30s. Patchy frost will be a possibility come Friday morning.
Frost Friday Night:
Looking ahead to Friday, quieter but cooler weather settles into northern Illinois. We'll see a mix of sun and clouds, with an isolated sprinkle or shower possible at times, though many will staydry. Highs will top out in the low 50s, running below-average for this time of year. As skies partially clear into the late-evening and overnight hours, the potential for frost increases into Saturday morning.
The cooler weather has settled in for the next few days and to go along with the chill will be the daily chance for a few sprinkles/light rain showers. The first of which arrived this afternoon and evening. Locally the precipitation hasn't been much, as most of the steady rain has fallen north of the state line in Wisconsin, but a few sprinkles and light rain showers have dotted the skies across southern Wisconsin and northern Illinois over the last few hours. You can see one of those showers on our SkyTrack camera in Beloit, WI.
The precipitation will come to an end as the sun sets Wednesday evening, leading to partly cloudy skies overnight. As the wind eases tonight the potential for some patchy frost will be possible, especially where temperatures are able to drop into the low to mid 30s.
Temperatures Thursday will once again struggle to make it above the mid/upper 50s under partly sunny skies. Northwest flow within the jet stream will send a few upper-level disturbances our direction, with the next one expected Thursday afternoon. Similar to Wednesday, this will give us a chance for some light precipitation during the afternoon and early evening. Rainfall amounts are not expected to be much - adding up to just under a tenth of an inch - but you may need the jacket or umbrella for a brief time Thursday afternoon.
As the sun sets Thursday night skies will clear out once again allowing temperatures to drop into the low to mid 30s. Patchy frost will be possible early Friday, followed by the chance for some scattered precipitation Friday afternoon. Highs will remain in the mid-50s.
High pressure moving in Friday night will give us a better chance for some widespread frost going into Saturday as temperatures area wide drop back into the low 30s.
Sprinkles, light showers, and cloud cover will hang around early, but we should see improvements slowly spill in as the day progresses. Though we see a mix of clouds and sun, a northwest wind will usher in cooler air, liming afternoon highs to the upper 50s. With a bit of moisture and lift still in place, a brief, isolated sprinkle remains possible later today.
Tonight, skies will gradually clear and this round of cooler air will continues to spill in. With lighter winds and little cloud cover, temperatures will drop off efficiently, allowing overnight lows to fall back into the upper 30s by Wednesday morning.
Chilly Nights Ahead:
Looking further down the road, even cooler nights are on the way. By Friday night into Saturday morning, temperatures may dip low enough to allow patchy frost to develop. If you have any sensitive potted or newly planted vegetation, it would be a good idea to bring them indoors or cover them.
It was a pleasant and seasonable day in the Stateline Tuesday as afternoon high temperatures pushed into the low 60s for most, topping out at 64 in Rockford. This came with a lot of afternoon sunshine, but the evening began an increase in clouds from the West.
Light rain showers are set to follow those clouds, with initial rain pushing in after 8-9PM. Rain will not come down hard, but there may be a couple brief pockets of steady rain at times through the night. Temperatures will only drop into the mid 40s with the clouds and added moisture from falling rain.
The last of the showers will exit after 6-7AM Wednesday. All told, up to 0.25" may come down before Wednesday morning. A very slim chance of a sprinkle may be realized Wednesday afternoon, but most of the day will be dry with highs in the upper 50s.
But the cooler stretch doesn't go anywhere this week. The next 4 days in a row (Wednesday through Saturday) are currently forecast to see afternoon highs fail to reach 60 degrees and remain in the mid or upper 50s. Overnight lows will be accordingly chilly, down in the 30s for a few nights. Depending on cloud coverage and surface winds, we could be in store for some patches of frost Thursday and Friday nights in particular!
April has lived up to its reputation in Rockford, with enough rain to rank the month as the 6th wettest April on record through 27 days. That same soaking rain from Monday also played a key role in the Stateline's severe weather potential, shifting the highest potential well to the southcloser to St. Louis.
Cooler Tuesday:
Looking ahead, conditions across northern Illinois will gradually improve as clouds break apart from west to east. That clearing will come with a noticeable northwest wind, ushering in a cooler, drier air behind Monday's frontal passage. Even with a bit of sunshine, temperatures will top out at seasonable-levels, settling in the low 60s.
Clouds will increase this evening as a weak system moves in from the northwest. While most of the area will stay dry, there may be just enough lift for a few isolated sprinkles to develop, mainly late this evening into the overnight hours.
Rain amounts, if any, would be very light, with no impacts expected. Afternoon highs will end up even cooler Wednesday as we keep a cool northwesterly wind, which will limit highs to the upper 50s.
The storms this morning didn't pack much of a punch along the leading edge like thunderstorms typically do. But immediately behind the storms, there was a strong push of Easterly winds called a "wake low". This small-scale area of low pressure can occasionally develop behind an outgoing complex of storms, bringing sharp pressure drops over small areas. Air rushes in to fill the void left behind, causing the strong winds in the wake of those storms.
Weather observer Fred Demeter near Stockton recorded this wake low with a barometer. He measured a drop of 0.3 inches of mercury (7-10 millibars) in barometric pressure in just 10 minutes. That also came with a period of gusty East or Southeast winds, above 50 mph from Fred's measurements.
It wasn't just Stockton that saw the winds either. Much of the area saw at least 40 mph gusts in the wake of those storms. DeKalb, Freeport, and Galena each observed 50+ mph wind gusts. Some scattered tree damage was reported across parts of Rockford with extensive damage in parts of DeKalb and Kane Counties. A 70+ mph wind gust was even reported in Milwaukee with more widespread damage. A wind advisory was issued as this wake low began developing and was upgraded to a high wind warning for DeKalb, McHenry, and Kane Counties once the threat for damaging non-thunderstorm winds was imminent.
While wake lows are not all that common, it is a reminder that strong winds can occur outside of thunderstorms too!
[11:00PM] Storms are exiting out of the area to the East as of 11PM, allowing conditions to dry out overnight. Behind a cold front, winds will turn to the West, gusting near 25 mph at times. This front will also bring in much cooler air by morning with temperatures pushing into the mid/upper 40s.
[10:00PM] The last of the isolated storms have now pushed East of I-39. While these storms are still not severe, they have continued to produce lightning and pockets of heavy rain. A few instances of gusty winds may be possible. Storms will clear Eastern McHenry County after 11PM.
[8:00PM] This thunderstorm in Eastern Jo Daviess County is not severe, but is capable of producing 50 mph wind gusts and penny sized hail as it moves to the East at around 30 mph. This storm will move near Freeport within the next 20 minutes.
[7:00PM] Scattered thunderstorms continue to progress to the Northeast and will move across the Stateline through 9PM. At the moment, neither area of storms is severe, but both are producing pockets of lightning and heavy rain. If storms intensify any, gusty winds and small hail may also be possible, but severe threats do not appear imminent at this time.
[5:40PM] Thunderstorms in Iowa are beginning to perk up a little bit with an isolated severe storm near Cedar Rapids. Additional storms are also forming along I-80 and pushing Northeast. Scattered storms will remain possible through 8-9PM. Still watching for a lower-end risk for damaging winds and hail within the strongest storms locally.
[4:30PM] The atmosphere is trying to destabilize after the morning round of storms came through. Much better instability is fueling severe warned storms mainly South of I-74, while storm coverage will gradually increase locally through 5-6PM.
Strongest storms may be able to produce gusty winds and small hail, with a relatively lower severe risk. Not out of the woods entirely but heading in the right direction! Last of the storms will exit the area after 9PM, as temperatures fall back to the mid-40s tonight.
As we look ahead to later today, we're continuing to monitor the potential for strong to severe storms. That said, rain expected during the late morning and early afternoon hours may limit how much the atmosphere can rebound or recharge. Because of this, the Storm Prediction Center has pushed the level 3 enhanced risk farther south, leaving the area under a level 2 slight risk for severe weather.
It's south of the warm front where the atmosphere will be very favorable for all severe hazards. Locally, we'll be watching how things evolve. IF this morning's rain and thunderstorms end up working the atmosphere over too much, our severe threat could be further reduced as we head into the evening. That said, a few thunderstorms will still be possible into early tonight as a cold front sweeps through the area.
Rainfall-wise, most spots could wind up with .25" to .75", with isolated totals up to 1". Cloud cover should stick around into Tuesday morning, then clear out some as we head into the afternoon. Highs will be limited to the low 60s as winds will remain breezy but cooler out of the west-northwest.
Trending Cooler:
With the cold front coming through, temperatures will trend cooler for the end of April. Normally, we are in the low to mid 60s. With troughing occurring in the upper-levels and northwest flow present at the surface, expect afternoon highs to drop into the upper 50s Wednesday, Thursday, and Friday. This runs 5° toas much as 10° below average.
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!
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!
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!
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.
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!
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.
