Forecast models continue to show a frontal boundary lifting north towards I-80 this afternoon. If that front is able to push a little farther north than currently expected, it could provide enough lift for an isolated shower or thunderstorm locally. Otherwise, most will stay dry through the day with partly cloudy to mostly cloudy skies. Afternoon highs remain seasonable, landing in the low 80s this afternoon.
Weekend Festivals:
For those heading to ByronFest or Tutty Baker Fest this weekend, the forecast cooperates. Rain chances remain low as high pressure settles into the region, bringing a mix of clouds and sun. While the weather stays largely dry, the heat will slowly begin to build back into norther Illinois. Afternoon highs are expected to reach the upper 80s each day, creating warm conditions for outdoor events. So while having a good time, drink plenty of fluids.
Warm Up Continues:
Looking ahead to next week, summer heat will make a noticeable comeback as a strong ridge builds across the northern Great Plains and the Great Lakes. This will allow temperatures to climb up to the 90-degree mark Monday, with several consecutive days of 90-degree heat possible until Thursday.
The National Weather Service issues many different type of warnings, including severe thunderstorm and tornado warnings. Both of which cause damage but have many differences in extent of damage. Most thunderstorms do not do much damage, but once you get closer to 60+ mph winds, larger limbs can be broken, and small trees can be uprooted. Above 80 mph is when structural damage is possible if not likely.
Once you get up toward 60-80 mph, that is equivalent to a weak tornado. An EF0 tornado ranges from 65-85 mph, while EF1 is when winds reach 86-110 mph. While the most destructive tornadoes do much more damage, those are very rare. Only around 5% of all tornadoes reach EF3 intensity or greater.
The damage paths of tornadoes vary greatly from straight line winds as well. A swath of straight-line winds can be around 5 miles wide, stretching across the core of the thunderstorm itself. Tornado damage may be confined to a much narrower area, as even larger tornadoes may only be a mile at their widest. That means the damage paths may be much more widespread from severe straight-line winds than tornadic storms.
Severe thunderstorm warnings from the National Weather Service can fall into one of three categories: Base, Considerable, or Destructive. A Base severe thunderstorm is for winds of 58+ mph and/or quarter sized hail. Considerable would indicate 70+ mph wind gusts and/or golf ball sized hail are possible. And a Destructive tag is for a severe thunderstorm capable of producing 80+ mph wind gusts and/or baseball sized hail. A Destructive severe thunderstorm will trigger the wireless emergency alerts (WEA) on your cell phone, like all tornado warnings do regardless of strength.
A "tornado possible" tag is also utilized within a severe thunderstorm warning when there is broad rotation, conditions favorable for rotation, or the storm has had a history of producing tornadoes. That "tornado possible" tag is a way to alert the public that a quick spin-up tornado can occur but is not imminent at that time.
You will often hear our weather team say "treat this severe thunderstorm warning as if it were a tornado warning." That is partly because of the larger coverage of damage than can be done, but also because the intensity of some severe storms can be equivalent to that of a weak tornado. Severe thunderstorm warnings will NOT automatically trigger your cell phone unless they reach 80 mph winds.
This is why it is important to have many ways to receive those warnings. Weather apps on your phone, including the "First Warn Weather App", can send push notifications for all severe thunderstorm warnings. Weather radios will broadcast warnings, watches, and other important weather information. Simply relying on your phone and tornado sirens will not alert you for all hazardous weather.
Hopefully this article has given some context behind why some storms have tornado warnings and others don't, the strength of some severe storms, and additional resources you can remain weather aware and stay safe during the storm season and the rest of the year.
A mix of sun and clouds Thursday afternoon allowed temperatures to warm into the low to mid 80s with a heat index reaching the low 90s. The majority of the afternoon has been dry, outside of a few showers that moved across northern Illinois and southern Wisconsin earlier in the day.
We will see a gradual increase in showers and isolated thunderstorms through the evening as the combination of a lake breeze from Lake Michigan and cold front move across southern Wisconsin and northern Illinois. The biggest impacts from any shower/storm that develops will be periods of heavy rainfall. There may also be some gustier winds through sunset. The chance for rain will last through Midnight, perhaps even as late as 3am/4am Friday.
As the showers come to an end the light northeast wind and increased low level moisture could lead to some areas of patchy fog through Friday morning. While I am not anticipating anything too widespread or dense, locally dense fog will be possible for some during the morning commute.
Similar to Thursday, temperatures Friday will warm into the low to mid 80s. We may see an isolated shower/storm, or two, Friday afternoon but the majority of the area will remain mostly dry. Temperatures through the weekend will warm into the mid and upper 80s before reaching the 90s next week.
A weak frontal boundary will slowly drift through the Stateline today, bringing a mic of clouds and sun along with the chance for a few isolated showers and storms. Not everyone will see rainfall, but a brief downpour or two and even a rumble of thunder can't be ruled out this afternoon and evening. Behind today's frontal passage, temperatures will be a smidge cooler compared to the last few days, with afternoon highs peaking in the low 80s.
The threat for severe weather later today into tonight remains rather low across the Stateline, as the highest potential will stay well to our south. Currently, the Storm Prediction Center has placed portions of central Missouri, southern Illinois, and southwest Indiana under a level 2 Slight Risk for scattered thunderstorms. Closer to home, northern Illinois and southern Wisconsin remain under a general thunderstorm risk, meaning widespread severe weather is not expected today.
Chances May Linger:
Friday looks to be even drier as high pressure builds into the northern Great Lakes region. Patchy fog may develop early in the morning, especially in low-lying and rural areas, before giving way to a mix of clouds and sunshine during the afternoon. While most locales will remain dry, an isolated shower or storm cannot be completely ruled out. Afternoon highs will end up similar to today, in the low 80s.
A warmer and slightly more humid air mass will spill into the Stateline today as temperatures climb into the upper 80s under mixed sunshine. While much of the day will be dry, our attention turns to a slow-moving boundary approaching from the northwest.
This boundary will serve as the focus for storm development across central and southern Wisconsin later today, with a few thunderstorms drifting south into northern Illinois overnight into Thursday. While a couple of storms could become strong to severe, the overall threat remains limited, which is why the Storm Prediction Center has placed areas north and west of Rockford - including Freeport, Machesney Park, and Poplar Grove, under a level 1 of 5 Marginal Risk.
Rain Chances Linger:
A weak disturbance passing to our south on Thursday will provide enough lift to spark an isolated round of showers and thunderstorms, particularly late in the afternoon and into the evening. While a stray storm cannot be ruled out, the severe weather threat across northern Illinois remains extremely low. The highest risk for stronger storms will stay well to our south across portions of central Missouri and the southern half of Illinois. With a few more clouds around and slightly cooler air filtering in on the northern side of said disturbance, afternoon highs will drop back closer to average, landing in the low 80s. Little change is expected for Friday as high temperatures remain in the low 80s with partly cloudy skies emerging by the afternoon.
The summer-like temperature trend has been prevalent as of late, with afternoon highs in the low to mid-80s. Under the influence of high pressure, we have remained dry so far. But as the high pressure moves away Wednesday evening, thunderstorm chances will be on the rise into Thursday.
A cold front will slide our direction from the North Wednesday evening, producing scattered thunderstorms across Iowa, Minnesota, and Wisconsin. As that cold front slides Southward later in the day, a few storms may reach our Southern Wisconsin counties after 7-8PM. Most of the Stateline may remain dry until later in the night.
The strongest of the storms may pose a risk for some gusty winds and heavy rain, but in an isolated to scattered fashion. Given the later evening timing for us locally across the Stateline, our overall risk for severe weather will not be as high as areas to the North where storms will be more numerous during the daytime. Portions of Southern Wisconsin are under a Level 1/5 Marginal risk for severe storms.
As the cold front settles South of us for Thursday, additional thunderstorms may remain possible. Similar to Thursday, it will not be very widespread for everyone. A remnant wave from previous day's storms may help to enhance thunderstorm coverage across Central Illinois, leaving us a bit more isolated across far Northern Illinois.
Still, the strongest storms may pose a risk for some gusty winds. Much of Illinois is under a Level 1/5 Marginal risk, which stretches up into parts of the Stateline. There will be lots of dry time Thursday, but the strongest storms may still bring a risk for heavy rainfall as well. Areas that saw heavy rainfall over the last week or two may need to be especially cautious for flash flooding potential.
A few isolated storms may persist into Friday as the cold front stalls just South of the area. Temperatures will only reach back into the low 80s as a result. The next round of high pressure takes over by the weekend, drying things out. Following that high pressure, another increase in humidity will arrive early next week.
Tuesday brings more of the same comfortable summer weather we enjoyed on Monday, with just a little extra warmth. High pressure remains firmly in place across the western Great Lakes, keeping conditions quiet with mix of clouds and sun. As a result, afternoon highs will climb a few degrees higher compared to yesterday, reaching the upper 80s. All in all, it will be another pleasant July day with very little to disrupt outdoor plans.
Midweek Storm Chances:
Wednesday looks to stay mostly dry as temperatures continue their upward trend. Most Stateline locales should reach the upper 80s. Winds will begin out of the southeast before gradually turning southwesterly later in the day as a cold front approaches from the northwest. This boundary will have enough support to spark up our next chance for showers and storms, with the highest potential residing north of the Illinois/Wisconsin border. That is where the Storm Prediction Center has placed areas under a level 1 of 5 Marginal Risk with areas further north into Wisconsin being placed under a level 2 of 5 Slight Risk.
Current indications suggest much of this activity will weaken as it approaches northern Illinois, limiting both coverage and intensity. Even so, a few showers and thunderstorms cannot be ruled out overnight into the early stages of Thursday. Additional rain and storm chances may persist into Thursday afternoon and evening as a weak area of low pressure (M.C.V) slides into the central portions of Illinois. At this point, the better chance for heavy rainfall to the south of interstate 88, but something to monitor as we get into the second half of the week.
