Scattered storms possible today, hit-or-miss this weekend

What is an M.C.V?:

Thunderstorm chances are back in the forecast today, and it all ties back to something we call an M.C.V, or Mesoscale Convective Vortex. This is essentially a leftover spin in the atmosphere that develops within a cluster of showers and storms. Even after the main storms weaken or move out, this compact area of low pressure can linger and act like a spark for new storm development. The added spin from an M.C.V could also enhance the threat for weak tornadoes. 

Today's Severe Threat:

As for the severe threat today, areas south of highway 20 in northern Illinois are under a level 2 of 5 - slight risk for scattered strong to severe storms. It's not a slam dunk setup, though. Earlier rain and storms have worked the atmosphere a bit, which could limit how much additional thunderstorms is able to develop later on. That said, if storms could tap back into some of the available storm fuel, a few could become strong with gusty winds and heavy downpours. And while the overall threat remains on the lower end, it's still worth keeping an eye on, especially in the slight risk area where the spin will be enhanced due to the incoming M.C.V. 

For those who miss out on any of the scattered storms this afternoon and evening, it'll be a different story. Conditions will stay dry, partly cloudy, but noticeable more humid, with that muggy feel really settling in. Even without the rain, it'll be a summer-like finish to the day with afternoon highs in the low 80s and dew point temperatures in the upper 60s.  

  

Weekend Outlook:

Thunderstorm chances on Saturday look to be more isolated and pulse-like, meaning we're not expecting much in the way of severe weather. Instead, a few individual storms could quickly pop up during the heat of the afternoon, briefly intensify, and then fade just as fast. So hit-or miss. Some will see rain and others will not. Most areas however will stay dry with highs climbing into the mid 80s. As we head into Sunday, most of the daylight hours should stay dry with a mix of clouds and sunshine. Rain chances hold off until later, with the next opportunity for showers and thunderstorms arriving during the overnight hours Sunday night. 

Drought conditions expand across Northern Illinois following dry May

 May was an exceptionally dry month in the Stateline, for Rockford in particular. Only 0.52" of rain came down all month at the Rockford airport, making it the second driest May on record. It was similarly dry across much of the region as well. Maps below show the accumulated rainfall and percent of normal over the last 30 days, highlighting much of the Stateline region that has been exceptionally dry over the last month. Some locations have only seen less than 1/4th of "typical rainfall over the last 30 days!

Last week, the Climate Prediction Center indicated that much of the area was under risk for "Rapid Onset Drought". Just a week later, much of that same area is now under a Moderate Drought from the latest Drought Monitor. This has been rapidly expanding, given that just 3 weeks ago only a small part of Northern Illinois was considered "Abnormally Dry".

Some much-needed rain may soon be on the way, with repeated rounds of showers and thunderstorms starting Friday morning. While the rain will not be uniform and soaking rain for everyone, the additional waves will result in higher rainfall potential for everyone. Latest forecast models and the Weather Prediction Center suggest around 0.5-1.0" may be possible over the last 5 days, with higher amounts within scattered thunderstorms that may develop. Not totally drought-busting, but it would be more rainfall than we've seen in quite a while!

Thunderstorm chances increase Friday morning

 

Our stretch of comfortably warm weather will soon come to an end as a more summer-like pattern is set to return heading into the weekend. This means temperatures will not only remain in the 80s through the weekend, but we'll soon feel the return of higher humidity.

For the rest of Thursday evening clouds will slowly increase but our skies will remain dry. A line of non-severe thunderstorms stretches from northern Wisconsin back southwest through Iowa and northwest Missouri and will slowly move east through the night. High pressure over the Great Lakes has kept quite a bit of dry air in place as moisture continues to build west of the Mississippi River. Eventually, that moisture will move east which will lead to those storms moving into northwest Illinois around daybreak Friday. While in an overall weakening trend can be expected, the scattered showers/storms will move across northern Illinois and southern Wisconsin through late morning.

Friday afternoon will likely see some dry time as only an isolated threat for a storm or storm will be possible. Surface winds from the southwest will keep temperatures in the low 80s but push dew points into the 60s. This will make the afternoon feel quite a bit more humid than what it has the last several days.

The rain during the morning won't be evenly distributed across the region, leaving some to receive totals nearing a half an inch to three quarters of an inch while others may not get quite as much. The next chance for showers and thunderstorms will return late Friday evening from what develops to our west and northwest during the late afternoon and evening. The highest threat for strong to severe storms will remain west of the Mississippi River during that time, but the remnants of those storms could move in our direction Friday night posing at least an isolated risk for a strong/severe storm or two. Because of this northern Illinois and southern Wisconsin remain under a 'marginal risk' for an isolated strong storm or two.

Warm, breezy today—storm chances return Friday

Warmup Continues: 

Yesterday was another beautiful day, though it gave us a true taste of summer with highs climbing into the low to mid 80s across the region. Today, we turn up the heat a bit more as southwesterly winds become better organized, helping boost temperatures even higher for our Thursday. Expect afternoon highs to top out around 87 degrees beneath a partly cloudy sky. It'll be a bit breezy at times, with gusts reaching up to 25 mph this afternoon.  

Rain Chances Increase:

Cloud cover will begin to increase this evening as our next system organizes to the west. Even so, forecast models continue to slow down the eastward push of developing showers and thunderstorms, keeping most of the activity just out of reach through much of the night. As it stands now, the better chance for rain looks to hold off until closer to daybreak tomorrow morning, when that line of showers and storms finally works its way into the Stateline. 

Severe, Flash Flood Potential:

Another round of showers and storms is expected to fire up over Iowa by Friday afternoon, and where these storms form and track will be key for us here in the Stateline. That placement will play a big role in both our severe weather potential and the risk for flash flooding heading into Friday night and Saturday morning. Right now, the Storm Prediction Center has much of the Stateline under a Marginal Risk (isolated threat) for strong to severe storms, while the Weather Prediction Center has placed half the region under a Slight Risk (15%) for excessive rainfall and possible flash flooding. Precipitation chances should diminish or taper off Saturday morning as the main upper-level feature pushes to the east of the area.    

 

Prospects for much-needed rainfall increase into the second week of June

 While the last month plus has been rather dry across the Stateline, but we may begin to see more of a pattern change on the way before too long. We will see a few chances for at least scattered showers starting late this week and toward the weekend, particularly over Friday.

Another favorable window for some downpours or storms will arrive early next week. Abundant gulf moisture will inch Northward after Sunday, bringing increased rain chances toward Monday-Tuesday in particular. The deeper "Precipitable Water" values indicate more moisture than could be rained out given the right conditions.

Even subtle waves in the atmosphere will be able to produce scattered downpours, and that looks likely between Monday and Tuesday. That rainfall may not be widespread for everyone at any given time, but more locations than not should be able to see some of the beneficial rainfall early next week.

Rainfall coverage will be key in determining how much of the Stateline sees this soaking rain potential versus those who don't. Monday and Tuesday will probably be between 40-60% coverage, meaning only around half of the area will see rain at any given time. I'm not expecting the rain to be overly widespread, meaning there should be at least some dry time between waves of rain.

Even though the rain will not be overly widespread for everyone, the rich moisture will result in heavy downpours when rain does fall. Through the week, that will begin to add up with some rainfall for many locations around the region. Computer models may not have an easy time predicting how much widespread rainfall we will see this far out due to the scattered nature of the showers and storms. That said, there is an increasing chance for most of the area to see a half inch or more of much-needed rain through mid-next week.

Warm-up well underway, few storms possible by Friday

Warmer Wednesday:

It's been a stellar start to June, with plenty of sunshine and highs hovering around 80-degrees - about as nice as it gets without high humidity levels. That quiet, comfortable weather pattern sticks around today as high pressure remains in control, keeping skies partly to mostly sunny. With a light southerly breeze, highs will tick up a bit compared to Tuesday, pushing a bit further into the low 80s, right around 84.  

Rain Chances Increase:
 
Thursday brings a bit more heat, with temperatures peaking in the mid to upper 80s. Along with the above-average warmth, expect an increase in cloud cover by the afternoon, which may be enough for a stray sprinkle or passing shower. 

  

Rain chances look a bit more promising on Friday, especially as we get into the afternoon. Showers, and even a few thunderstorms cannot be ruled out as the day unfolds. Right now, forecast models are honing in on the higher rainfall totals staying just to our north and west, but some areas could still pick up close to a half inch of rain - or even a bit more. 

  

As always, how much we see will ultimately depend on how Friday's rain and storm chances materialize. Severe potential is low but an isolated severe storm or two will be possible given the amount of energy, moisture, and lift in the atmosphere. 

For that, the Storm Prediction Center has placed the entire Stateline area under a level 1 of 5 Marginal Risk, with a higher potential for severe storms across Iowa and southern Minnesota. 

Warm & quiet through Thursday, unsettled by the weekend

Ridging Remains:

June is off to a great start across the Stateline. Despite a bit of cloud cover at times yesterday, temperatures still made a comfortable climb into the upper 70s, giving us a really pleasant early-summer feel. And this pattern isn't going anywhere soon. 

A ridge of high pressure remains firmly in place in the upper-levels of the atmosphere, helping to steer away any meaningful rain chances away today, tomorrow, and for much of Thursday. Expect afternoon highs to peak in the low 80s this afternoon under plenty of sun. Low 80s are also on the table for Wednesday, though expect there to be a few more clouds.  

Ridge Breaks Down:

Forecast models then show a change happening as we get closer to the weekend. That ridge begins to break down a bit, opening the door for a few shortwaves or upper-level disturbances to pass through. 

 

  

This setup will help a pull a plume of richer moisture northward into the Midwest and the western Great lakes, adding a little more fuel to the atmosphere. As a result, rain chances, along with the potential for a few storms, will tick upward, especially Friday and during the day Saturday. Currently, it doesn't look like either day will be a washout. 

Even with the added clouds and chances for rain, temperatures will stay on the warmer side, peaking in the low to mid 80s. Overnight low remain on the mild side, ending up in the low 60s.