Blocking pattern keeps us dry and increasingly warm next week

 After some widespread to scattered showers Thursday into Friday, things will dry out as we head into the weekend and beyond. A blocking pattern aloft in the atmosphere will set up early next week, with a cutoff low pressure sitting to our South and a ridge of high pressure to the West. This will limit our precipitation chances and bring a gradual warming trend through much of next week.

First with the warmth: The next few days will remain relatively cool and closer to average with rain showers Thursday and Friday but drying out for Saturday. By early next week, temperatures will be on the rise, likely reaching well into the 70s by Tuesday.

The only slim chance for rain after Friday comes within the cutoff low drifting over Ohio and Indiana Sunday into Monday. If this were to trend further West, we might see a few light showers. But for now, I have maintained a dry forecast during this time. The next better chance for any precipitation looks to arrive toward the end of the week.

We definitely could use the rain. So far, the month of April has only brought 2.16" of rain to the Rockford airport, over an inch and a half shy from the normal mark through today's date. Meanwhile, the annual rainfall is just 6.23", more than three inches short of the average mark of 9.38". Moderate drought has been expanding across portions of Northwestern Illinois, while much of the Stateline has been identified as "abnormally dry" according to the latest drought monitor from the National Drought Mitigation Center. May is typically the 3rd wettest month of the year, so hopefully we can make up some of the difference over the next several weeks.

Couple chances for rain ahead, heaviest arrives Thursday

For the second consecutive day, the Rockford Airport saw a peak wind gust over the 35 mph mark. Moving forward, gusty winds take a break, though a couple of weaker disturbances will result in sporadic and at times steady rain chances.

 

 

 

Wednesday begins with some sunshine, though we can expect skies to cloud over towards midday as our next weather system approaches. Rain will be quick to follow, most likely arriving late in the afternoon and in a scattered fashion. Once rain begins, it’s likely to fall off and on overnight through Thursday evening, with the heaviest rain arriving as Thursday's morning commute gets underway.

In the end, most locales should wind up with .25" to .75". We do see a break in the precipitation Thursday night into early Friday morning, though another weak disturbance may bring rain chances back in to the equation during the day Friday. This activity would be more scattered in nature compared to the rain that takes place Wednesday and Thursday, allowing more dry hours to mix in. Afternoon highs remain in the low 60s until Sunday where milder air spills in, pushing temperatures back into the 70s.

Soaking rain returns late Wednesday, continues Thursday

 

Temperatures took a tumble Tuesday following the passage of a cold front bringing us down from the 70s we started at just before sunrise, into the upper 50s around Noon. But with the return of sunshine, we've been able to warm back into the 60s.

Rest of this evening/overnight:

Cloud cover from the ongoing showers and thunderstorms to the south will continue to clear as high pressure moves into the Upper Great Lakes. This will allow our winds to ease through the evening and temperatures to fall into the upper 30s and low 40s. Winds will remain from the north/northeast.

Wednesday:

High pressure will slide into the eastern Great Lakes during the morning which will turn our surface winds to the southeast Wednesday afternoon. As a warm front approaches from the southwest cloud cover will be on the increase, turning skies mostly cloudy by Noon. The first half of the day is expected to remain dry with the influence of high pressure still in play. But as the high fades further to the east, low pressure will begin to move in allowing moisture to increase by Wednesday evening.  This will allow for the return of showers, with a few embedded thunderstorms, by Wednesday evening and overnight.

Temperatures on Wednesday afternoon will warm into the mid-60s but won't drop much thanks to the return of a warm front. This front will reach the state line early Thursday morning before shifting back down to the southeast Thursday afternoon. A few embedded thunderstorms will be possible during that time, but the severe risk will remain low. The rain will become more widespread late Wednesday evening and overnight.

Thursday:

Scattered showers and thunderstorms will be ongoing Thursday morning, continuing into the afternoon. It's during this time that we should see most of our rain accumulation, which could add up to just under an inch for some.

Temperatures on Thursday will stay in the 60s but fall with the turn of the wind back to the northwest during the afternoon and evening. Low pressure passing just to the south may give us a brief break from some of the rain during the early afternoon, but scattered showers will return on the backside through the evening. Additional showers will continue Friday afternoon with temperatures back into the low to mid 60s.

Rainfall totals will reach at least half an inch but could approach an inch for some by Thursday night. The soaking rain is much needed as we've built up a rainfall deficit for the month of April of nearly an inch and a half. Following the passage of the low Friday high pressure moves back in for the weekend with dry and quiet conditions. Temperatures will warm into the 60s Saturday and then 70s for Sunday.

Temperatures across northern Illinois fall back following Tuesday's cold front

The work week began with a taste of summer as highs surged into the low to mid 80s. Though strong winds played a major role into Monday's significant warm up, the milder air these winds provided us with ended up being our "saving grace" so to speak from the late-day  severe weather potential. 

How so? Well, the milder air put a "cap" or lid on our atmosphere. For thunderstorms to properly evolve and rapidly turn severe, you need the temperature profile in that section of the atmosphere to cool from the surface to the upper-levels. 

However, if there is a layer of warm air roughly 5000 to 7000 ft above the surface, this prevents the air from rising, limiting storm growth and development. Now, if the cap were able to break, the air could keep rising, allowing clouds and storms to grow. Fortunately for us, the cap held strong, putting a lid on our severe potential despite there being a very conducive environment for severe storms in place. The storms that did manage to form in the system's warm sector remained to our north and west, leaving us fairly dry into Tuesday morning.

On the backside of this morning's cold front, clouds will decrease, leaving us with a good amount of sun for the afternoon. However, winds will remain quite gusty, especially during the morning. And this time, winds will be blowing out of the northwest. This will cool temperatures from the upper 60s this morning, into the low 60s by the afternoon. 

 

 

Cloud cover will return Wednesday as our weather pattern turns a bit active once again. Waves of showers and thunderstorms are likely to sweep through as early as Wednesday afternoon, and will continue off and on through Thursday, Thursday night, and even into early Friday.

Monday afternoon storm update: Isolated storms remain possible through the night

 

6:40pm Update: A line of showers and isolated thunderstorms have developed and are currently moving through northern Illinois, with a storm centered over Byron. The risk for severe weather remains low, but a few of the storms through 9pm could have some heavy downpours, frequent lightning, and small hail.

It feels more like mid-summer rather than late April as temperatures have soared into the 80s, with Rockford's 5pm temperature currently at 85 degrees. South winds have also been strong gusting to 45 mph throughout much of the afternoon.

Outside of the warmth and wind our afternoon has been fairly quiet with regards to any showers or thunderstorms. That's because the warmth - not only at the surface, but aloft - has put a cap, or lid, on our atmosphere. You may have noticed over the last few hours cumulus clouds developing but really struggling to grow in depth. This is a sign that the cap is in place and holding strong.

A weak disturbance moving through eastern Iowa has been trying to break the cap - as indicated by some of the clouds beginning to 'bubble' in eastern Iowa and southwest Wisconsin. A few light rain showers have also been trying to develop. So far, not much has grown with a lot of the activity falling apart. However, some of the showers southwest of Madison, WI have started to grow some, moving to the northeast. This activity will not impact the Stateline.

Over the next couple hours there remains an isolated thunderstorm chance, but the overall coverage isn't expected to be widespread. In fact, this looks to be at only about a 20% chance.

The next chance for storms will be with the arrival of the cold front itself which will move in well after Midnight. Ongoing severe weather near the Iowa/Minnesota border will continue to move east, further into Minnesota and northern/central Wisconsin later tonight. To the southwest, thunderstorms have started to develop west of Kansas City,
MO along the tail end of the cold front. As the front moves east through the night showers and thunderstorms may begin to fill in between the two ongoing areas of severe weather, moving into central Iowa and eventually into eastern Iowa. By this time, a lot of the instability we were able to build up during the day will have decreased, but instability aloft will remain somewhat sufficient for thunderstorms. If this line fills in and the storms are able to hold together through the night, then a few of the stronger storms would be capable of producing strong winds and hail locally.

On the other hand, it's also possible that the line doesn't fill in and we remain mostly dry, but warm, through the night. Overall - I think our risk for severe weather is on the lower end through the rest of the evening and overnight. But until the cold front passes it's best to remain weather aware and be prepared just in case.  

Severe storms still on the table this afternoon into Monday night

It was another fantastic day Sunday with lots of sun and afternoon highs in the low 70s. Temperatures remain on the upward swing for the start of the work week, though we'll have to monitor the potential for strong to severe storms.

The first of two warm fronts will lift through the region around daybreak, bringing with it a small chance for isolated showers and storms The risk with any of these storms is low, but some stronger ones could produce some hail. 

Once the morning precipitation and clouds clear, it should be a rather windy and warm afternoon. Southerly to southwesterly winds will gust around 40 mph at times as temperatures reach the upper 70s and low 80s. These warmer temperatures could put a lid, or cap, on our storm chances during the afternoon, however, that's not certain. The risk for severe storms, and possibly widespread severe weather, across the Midwest - including the Stateline - is there but it's conditional on a few things. And one of those things is the cap during the afternoon.

If the cap holds strong, then our risk for storms during the late afternoon and early evening would be lower. It wouldn't be zero, but it would be much lower than if the cap breaks. If the cap manages to break, then the environment would be prime for thunderstorms to evolve and rapidly turn severe. 

Some models this morning are getting a better understanding of today's storm evolution, showing a round of storms firing up near the Iowa - Minnesota border late in the afternoon, then bringing them towards the region this evening into early tonight. If this occurs damaging winds, tornadoes, and hail would all be a concern. For now, make sure you are staying up to date with the forecast and be prepared to adjust plans, if needed, for the late afternoon and evening hours. 

In their latest round of severe outlooks, the Storm Prediction Center has left most of southern Wisconsin and northwest Illinois in a level 3 of 5, Enhanced Risk for severe storms, with the southeastern half of the forecast area in a level 2 of 5, Slight Risk. The cold front should be through the region come daybreak Tuesday, leaving us cooler and drier with afternoon highs rolling back into the upper 60s.

Warm and windy Monday could lead to severe storms late in the afternoon

 

It was a beautiful Sunday afternoon with highs warming into the upper 60s and low 70s. Southeast winds did increase a bit from Saturday, but that didn't stop many from enjoying the outdoors. Temperatures Monday morning won't be as chilly as Sunday morning when many woke up to patchy frost and lows in the 30s. Monday will start with temperatures in the low 50s.

The first of two warm fronts will lift through the region Monday, with the first bringing a few isolated showers and thunderstorms to southern Wisconsin and northern Illinois around daybreak Monday. The risk with any of these storms is low, but some stronger ones could produce some hail. Once the morning precipitation and clouds clear, it should be a rather windy and warm afternoon. Southerly winds will gust around 40 mph at times as temperatures reach the upper 70s and low 80s.

These warmer temperatures Monday could put a lid, or cap, on our thunderstorm chances during the afternoon, however, that's not certain. The risk for severe storms, and possibly widespread severe weather, across the Midwest - including the Stateline - is there but it's conditional on a few things. And one of those things is the cap during the afternoon.

If the cap holds strong, then our risk for storms during the late afternoon and early evening would be lower. It wouldn't be zero, but it would be lower than if the cap breaks. If, on the other hand, the cap does break then the environment would allow storms to quickly turn severe - most likely forming in the Iowa/Minnesota/Wisconsin vicinity moving into southern Wisconsin and northwest Illinois. If this occurs damaging winds, tornadoes, and hail would all be a concern.

Unfortunately, the question marks on the severe potential and the when/where storms develop is still there. Make sure you are staying up to date with the forecast Monday and be prepared to adjust plans, if needed, for the late afternoon and evening. The Storm Prediction Center does have most of southern Wisconsin and northwest Illinois in an 'enhanced risk' for severe storms, with the southeastern half of the forecast area in a 'slight risk' for Monday.

Storms will also be possible during the late evening with the cold front moving through. These too, would have a severe risk with them, although a little lower than our earlier chance.  

Quiet weather today followed by warm and stormy day tomorrow

 

After another quiet day yesterday with high pressure sticking around, we can expect a very similar day today as well. High pressure won't be sticking around as long today ahead of our next weather system pushing in tomorrow but for most of the day, we'll see sunshine and continued comfortable temperatures.

Through the morning hours however, a few showers have worked their way through northern Iowa, which may begin to extend towards the state line but those shower chances this morning remain very isolated.

Into the rest of the day, we will once again have sunshine along with temperatures approaching 70! It'll be even warmer than yesterday however with a stiff wind out of the southeast today around 10-15 mph those temperatures may feel a little cooler.

Tomorrow though is the day we've been keeping an eye on the most as another dynamic low-pressure system is expected to move into the Midwest through the afternoon. Not many changes in the forecast have been made since yesterday as we're still a little unsure if storms will persist or weaken as they approach the state line tomorrow night.

Before diving into the storms, a bit deeper it's also important to note that with a passing low-pressure system we'll see windy conditions return. Through the afternoon the combination of low pressure along with sunshine heating the surface will allow wind speeds to be sustained near 20 mph while also pushing gusts up to 35 or even 40 mph.

Strong winds at the surface may also affect thunderstorm intensity as we head into the evening however there's two main ingredients we're focusing on right now which is atmospheric instability and the "low level jet."

The most important ingredient with thunderstorms is the instability as unstable air allows air to rise and create thunderstorms. Tomorrow, areas to our north and west will see much more instability than us allowing for more thunderstorm development. As night begins to set in instability tends to go down due to the surface cooling.

Our thunderstorm threat tomorrow is expected to be in the evening hours, which often in most cases sees decreasing instability into the night. Most forecasts for this event have kept true with that, however if instability hangs around into the evening thunderstorms will persist for a little longer.

Another key factor in tomorrow's forecast will be the nocturnal "low level jet." The low-level jet is normally a little less than a mile above us in the atmosphere and is often a focal point for severe thunderstorm forecasting. During the nighttime, we lose sunshine allowing temperatures to cool at the surface. The surface temperatures become cooler than the air above allowing for stronger winds to develop just above the pocket of cooler air. This then increases the amount of "shear" or how much our winds turn with height. When low level winds begin to turn this can help sustain thunderstorms along with give them a little more juice.

If thunderstorms persist through the night and into the state line tomorrow, they will experience a rather strong low-level jet. So, if thunderstorms do keep their strength as they move in the possibility of them staying severe will be there with the combination of low-level winds and instability. These ingredients will be known a lot more as we head through tomorrow, still through the day today make sure to go over your severe weather plan and make sure to have multiple ways to receive watches and warnings.

Warm and windy Monday ahead of severe storm chance late

 Our next storm system will arrive early this week, bringing a chance for some strong to severe storms Monday evening and Monday night. Before our storms, the morning and afternoon will be warm and windy with rising humidity, along with possibly a stray shower or thunderstorm. The higher potential and coverage will arrive Monday evening/night with a line of storms from the Northwest. These storms will likely be in some form of a weakening trend, but there is still a lot of uncertainty as to how much they will weaken before they arrive.

Storms will initiate well to our Northwest across portions of Iowa and Minnesota ahead of a cold front. This front will eventually draw the line of storms our way late Monday evening if not early into the night. Note the storms showing a weakening trend, but this is toward the end of the Futurecast model run, so we need to take it with a grain of salt this far out. The linear nature of these storms means the highest threats locally would likely be with damaging winds, but embedded tornadoes would also be possible within the line.

 

The environment ahead of these storms will be primed to keep them going late into the evening. The afternoon will see peak daytime heating near 80-degrees, along with dew points rising into the 60s. This will allow for a large area of high instability, or storm energy, to develop. Much of this energy will persist late into the evening ahead of the front.

Another factor storms use to maintain their strength is a strong low-level jet. This is an area of winds about five thousand feet above the surface. These winds help to enhance the forcing along the front, aiding to maintain that storm strength. The later into the night you go, the weaker instability will be, but the low-level jet may help keep the storms going.

That said, there is still a lot of uncertainty with how far South and East the severe threat will extend. But given the ingredients that look to be in place, a Level 3/5 Enhanced risk for severe weather covers most of the Stateline region around Rockford for Monday evening/night. The higher confidence in storms during peak daytime heating will remain further Northwest. There, a Level 4/5 Moderate Risk extends from Southeastern Minnesota into Western Wisconsin and down into much of Northern and Central Iowa.

The environment will be primed for severe storms across a broad region, but questions remain as to how far away from initiation the storms will maintain their strength. For now, action steps include reviewing your plans Monday evening and thinking ahead as to where you might go if severe warnings were to be issued. Also make sure to have a way to wake you up if there would be any warnings that would come out after bedtime! S

Severe thunderstorm chances increasing into Monday

 As we move into the last week of April, we've seen temperatures slowly creep up throughout the month to the point where yesterday's 60-degree temperatures almost felt cooler compared to the day prior! We'll see this pattern stick around into the weekend, however as we move towards the beginning of the week warm weather along with strong to severe thunderstorms look to return.

Today will be very similar to yesterday as we'll see another comfortable day with temperatures in the low 60's along with plenty of sunshine today! Wind speeds today will also be calm as high pressure both today and tomorrow will keep us seasonable with not much of a breeze to talk about! Temperatures will climb through the weekend but as we move into Monday, the chance for thunderstorms, some severe will return.

Storms will be forced along a cold front Monday evening which will bring the highest chances during the daytime for areas to our north and west. Heading into the nighttime though depending on how much instability hangs around, we could see these storms keep severe intensity into the night.

As talked about by most of the First Warn Weather team over the past few days, this system moving in on Monday has caught eyes for a few days in advance. The Storm Prediction Center outlined multiple long-range outlooks throughout the Midwest this week, however Monday's threat has now been upgraded to a 4/5 Moderate Risk for areas to our north and west. Areas in the moderate risk have the highest chance for severe weather, however into the nighttime storms that form to our north and west will dive south towards the state line into the night.

Zooming in a bit on the state line right now the severe thunderstorm risk is split nearly in half throughout the region. Most of the area right now is under a level 3/5 Enhanced risk into Monday night. As storms to our west grow into a fast-moving line strong downpours with lightning will be almost guaranteed however the severe risk currently outlines the risk for damaging winds along with a few brief and isolated tornadoes.

Instability will be the big question mark heading into the night though. As the sun sets a nose of warmer air or "cap" will begin to develop, depending on how strong this cap is we can either see thunderstorms continue at strength or weaken into the night.

Most models now have a fast-moving line segment or "MCS" moving through the state line as we head into the night. As previously mentioned, this type of system would most likely bring the chances of damaging severe wind gusts with it but a brief tornado cannot be ruled out all depending on how much instability we have into the night. Make sure to have multiple ways to receive watches and warnings into the night as well as keeping your phone volume on!

Luckily severe thunderstorm chances into Tuesday have begun to shift further to our south and east. On Tuesday we could see a few isolated thunderstorms hanging around through the morning however most severe activity will stay to our south and east. We look to cool down and dry off a bit into the evening then on Tuesday!

Severe weather potential increasing early next week

 The weekend will be a dry and somewhat pleasant one, but next week will start off on an active note. A strong surface low pressure system will develop to our West and Northwest Monday, eventually drawing a cold front through the area Tuesday morning. Ahead of this front, we will be increasingly warm and windy with a chance for some thunderstorms. Below is a look at the ingredients that would need to come together to form our chance for strong to severe storms.

Multiple ingredients have to come together to form strong or severe storms. Moisture is one of the most important ones. Ahead of the cold front, strong Southerly winds will feed lots of moisture into the Midwest region, raising dew point values into the 60s locally. Paired with temperatures near 80°, Monday will have a humid feel to it.

The moisture will aid to develop a lot of instability across the region as well. This is the atmospheric energy storms feed off of to develop. The highest instability will be primarily West and Southwest of us, but we will see a fair amount of it locally as well.

The main driver for these storms will be the cold front, but also the strong winds just a few thousand feet above the surface. This change in wind speed with height is called shear, which is another ingredient for storms. The strongest winds aloft will arrive Monday evening, perhaps providing the key to our timing of the strongest storms' arrival. Our window to watch for would be during the afternoon with some pre-frontal storms, then during the evening along the main line just ahead of the front.

The Storm Prediction Center continues to expand our severe weather risk for Monday, now spreading the higher risk into portions of Northwestern Illinois. The best ingredients look to form mostly West of the Rockford, but the line of storms will likely track through the area later into the evening. At the moment, my highest concern for any storms would be with damaging winds rather than tornadoes locally. There may not be as much spin in the atmosphere needed to form widespread rotating storms. That said, the threat is still more than a few days out, so be sure to stay weather aware over the coming days as the forecast becomes more refined.