Heavy rainfall, flash flooding increasingly likely Saturday night

A FLOOD WARNING has been issued for the Green River and nearby tributaries in Lee County until 7:15pm Sunday. Water from nearby fields and small creeks and streams continues to flow into the Green River basin which has caused flooding to a nearby campground - O'Connell's RV Campground. Due to the rising water, evacuations are underway.

Rises in the Green River are still possible through the afternoon as additional runoff continues to flow into the river. This will also be a concern for areas that are located downstream along the river. Please remain aware of any additional flooding that could occur throughout the day.

The Flood Watch that was issued for Winnebago, Boone, and McHenry counties has been canceled early, but remains elsewhere until 1pm. 

[11PM] Intense rainfall is now re-developing along I-88/I-80 corridors, pressing East and Northeast with time. Locally, the heaviest rain will move in after 12AM, and possible last through 7-8AM Sunday morning. At the heaviest, rainfall rates may be near 1-2" per hour. This will quickly turn to runoff over saturated soils, elevating concerns for flash flooding. Another 1-3" of rain will be possible area-wide, especially across Northern Illinois. The I-88 corridor appears to be the most likely location where a narrow axis of the most intense rain will fall, with some pockets of 3-4" or more possible near Sterling, Dixon, Oregon, and Rochelle. Please be sure to avoid driving through flooded roadways and be especially cautious at night when it will be difficult to see water over any roads. Rainfall will gradually wind down through the daytime of Sunday, but water levels may remain high well after rain ends.

Round one of the heavy rainfall event brought between 1-3 inches of rainfall across the Stateline, including a new daily record at the Rockford airport. Many weather watchers, shown in the purple boxes, also saw over 2" of rain. The heaviest rain last night was across parts of Jo Daviess County, where isolated pockets of 3-4" of rain or more fell. This has resulted in very saturated soils across the board, which will only enhance the flash flooding threat overnight.

I still expect the heaviest of the rain to arrive after 12AM, potentially lasting until 8AM. Another 1-3" may be possible, with some locations seeing locally higher totals where thunderstorms stall out. The highest confidence on such a corridor will be centered along I-88. Shower and storm coverage will gradually diminish through tomorrow afternoon, but a few pockets of steady rain may persist. Water levels may take a while to recede in some locations, so be on the lookout for flooded roads and low-lying areas well after the heaviest rain ends.

Futurecast showcases the heaviest rain moving in after 12AM, with some pockets of 1-2" rainfall rates. As rain comes down that heavy, it will be quick to runoff and pool in low-lying areas. If a narrow corridor of these rainfall rates sets up and stalls over the same location all night, the flash flood threat would be especially high.

The heaviest of the rain will begin to wind down after 6-8AM, but pockets of steady showers will remain possible through the afternoon and evening Sunday. While the rainfall rates will not be nearly as high, any stalling shower could quickly pond again on roadways and low-lying areas.

Flood watches remain in effect area-wide through early Sunday morning. With the widespread 1-3" of additional rainfall and isolated pockets of 3-4" or more over very saturated soils from earlier rains, the general region is especially susceptible to flash flooding tonight and early Sunday. Be sure to watch for flooded roadways and do not drive through them!

Heavy rain this weekend, flood watches in effect for Northern Illinois

 [10PM UPDATE] Things are still on track for some spots to see 1-3" totals tonight and early Saturday morning. As of 10PM, the heaviest rain is beginning to develop in far Northern Iowa and Southern Minnesota. That will be slow to progress Southward, likely not reaching the Stateline until after 2AM. If things keep up this track, the highest totals may end up *just* North of the Stateline, with best confidence on 2-3" totals in Southern Wisconsin. For everyone, the heaviest rain still looks likely between 3-10AM with most areas picking up at least an inch or two by midday Saturday. Additional rainfall could add onto those totals through Saturday afternoon and again overnight.

Multiple rounds of heavy rain will be possible this weekend, with main waves arriving Friday night and Saturday night. At the heaviest, rainfall rates may push 1-2" per hour, resulting in quickly piling up rainfall totals. The first wave of heavy rain is centered between 3-10AM Saturday morning. The afternoon will feature a few scattered showers and storms, before another round of heavy widespread rain will be possible Saturday evening and overnight.

The first axis of showers and embedded storms will arrive after 2-3AM, pushing across the Stateline from North to South. The rain itself will be slow-moving, with intense rainfall rates lingering over some spots for a couple hours at a time. If any embedded storms track over the same spots over and over, rainfall will add up rather quickly. The severe threat with these storms does not appear to be very high.

The heaviest of the rain will wind down after 10AM-12PM, but a few scattered showers and embedded storms may be possible through the daytime. Any storms that develop will add to rainfall totals, but this would be rather sparse in nature.

Another round of heavy rain may be possible Saturday night into Sunday, but the placement of this round is far less certain. If this round of heavy rain tracks over the Stateline region again, flash flooding will again be a concern with another 1-2" possible over already saturated soils.

All told between both rounds, up to 2-5" of rain may come down between Southern Wisconsin and around I-88/I-80 regions through Sunday evening. The highest confidence on flash flooding will be with heavier rainfall Friday night, but Saturday evening's round may also produce some flooding concerns if it follows the same path as the storms from the night before.

A flood watch is in effect area-wide from Friday night through Saturday. Heavy rainfall could cause flooding in low-lying areas, and rivers could rise to flood stage over the coming days with the heavy rain on the way. Remember to turn around, don't drown when you come across flooded roadways.

Flash flood watch in place for some Friday evening into Saturday

Thursday's Rainfall:

For the second time this week, the Stateline benefited from a healthy round of rain as showers and storms tracked along a slow-moving boundary. While the heaviest rain remained south of the Rockford Airport, where some locations picked up between 1-3 inches, much of the area received a good soaking. 

 

Flood Watch Issued:

The active and unsettled weather pattern is far from over, as additional rounds of rain are expected through the start of the weekend. In response to the potential for heavy rain, the National Weather Service has issued a Flood Watch for Jo-Daviess, Stephenson, and Carroll Counties in northern Illinois, as well as Green and Rock Counties in southern Wisconsin. 

Timing Out The Rain:

The first chance for rain arrives around midday in the form of a few isolated showers. The more impactful round of rain is expected to hold off until late Friday evening, specifically closer to or after midnight, as forecast models show a batch of showers, storms, and heavy rain pushing in from the northwest. 

  

This activity will likely persist through the pre-dawn hours before trending downward by mid-morning. From there, rain chances remain scattered through the afternoon and into Saturday evening. 

 

 

  

There also seems to be signs of another opportunity for showers and heavy downpours overnight Saturday into the first half of Sunday. All in all, totals may end up similar to what we encountered yesterday, with some locales picking up a more modest 0.50" to 1", while others could see 2" to 3", dependent on where the more intense rounds likely end up. 

Localized flooding from rainfall Thursday morning; More heavy rain on the way

 

Heavy rain came down Thursday morning with some locations picking up over two inches of rainfall! A brief flash flood warning was issued for southern Lee and DeKalb counties where radar estimated amounts of 3-5 inches occurred. Thankfully, the heaviest rain came to an end mid-morning with only drizzle and light showers continuing near and north of the state line into the afternoon.

A stalled boundary near Highway 20 allowed afternoon temperatures to warm into the low 80s along the I-88 corridor, while the 60s and 70s were found to the north. Drizzle and fog continued in southern Wisconsin but there have been some improvements over the last couple of hours. High pressure to the north will continue to sink down across the northern Great Lakes pushing the stalled boundary further south Thursday night. This will lead to mostly dry skies but could also lead to a little patchy fog through Friday morning. Temperatures will drop on either side of 60 degrees.

Friday morning will be dry, but mostly cloudy. We may see a few peeks of sunshine before clouds take over once again. This will be ahead of a northward advancing warm front that'll lift into northern Illinois late Friday night. Along the front a few showers cannot entirely be ruled out, developing from the west and southwest and moving to the east. These would move in during the late morning and early afternoon hours. By mid-afternoon the rain should be coming to an end with mostly dry skies through late afternoon and perhaps into early evening.

The next round of heavy rain is then expected overnight Friday into Saturday morning where another 1-3 inches area wide could come down. Following some of the recent heavy rainfall the last few days it's possible that localized flooding may occur in some spots. Most of the rain will be wrapping up mid-morning Saturday, but scattered showers with a few isolated thunderstorms can't entirely be ruled out through the afternoon. The coverage of any afternoon thunderstorms will depend on where the warm front ends up, which may be pushed further south with the rain in the morning. This would significantly limit the amount of warmth we would experience during the afternoon, resulting in temperatures staying in the 70s - and possibly 60s.

Another round of heavy rain can be expected once again Saturday evening into Sunday with the cold front moving through. An additional inch of rain will be possible during that time. In all, rainfall totals of 2-5 inches will be possible through the weekend. Rain chances become a little less into next week, but temperatures will be quite a bit cooler for the last few days of summer.

Showers and storms early, drying out this afternoon

Rainy Morning:

A stationary boundary positioned to the south of the Stateline has helped ignite a large area of showers and storms across eastern Iowa this morning, with that activity working its way into the Stateline. As a result, expect a wet start to the day and a rainy morning commute for anyone heading out. Rain will likely be steady, possibly heavy at times, especially underneath any thunderstorm. Overall, the severe weather threat remains low. However, some of the stronger thunderstorms could still produce heavy downpours, frequent lightning, and brief reductions in visibility. Allow for extra travel time and keep the windshield wipers working. 

Drying Out This Afternoon: 

Chances will be at their highest during the morning hours along the boundary. Conditions should then gradually improve this afternoon, with showers tapering off and drier weather beginning to work its way back into the Stateline. 

  

While an isolated shower can't be completely ruled out into the evening, most locations should remain dry under a mostly cloudy sky. Additional breaks in the cloud cover are expected overnight into early Friday as drier air filters in ahead of Friday's storm system. This setup will lead to an increase in chances for showers, thunderstorms, and periods of heavy rain late Friday evening, with these unsettled conditions lingering into the first half of Saturday. 

Light showers/drizzle move through northern Illinois Wednesday afternoon

 Temperatures have been running on the cooler side thanks to an abundance of cloud cover and a few light showers that have spiraled their way across northern Illinois. Rainfall amounts haven't added up to much, but our visibility has fallen in some locations where there is more drizzle/mist rather than light showers.

The showers have been the result of a few upper-level disturbances that have been moving overtop a strong ridge of high pressure to the south, which has brought significant heat to the south the last several days. That ridge will hold strong through the end of the week as it shifts a little further towards the southern Plains this weekend. We will remain to the north which will limit our overall warm-up during that time.

For the rest of Wednesday evening skies will remain cloudy with a little drizzle from time to time. Temperatures won't move much through the evening, holding steady into the mid-60s. We may even see some fog try to develop through sunset. A stronger push of moisture late Wednesday night will lead to widespread showers and thunderstorms developing after Midnight. This activity will move close to northern Illinois during the overnight, with the heaviest rain arriving after between 3am and 9am Thursday.

Flood Watches have been issued for Carroll and Whiteside counties beginning at 10pm Wednesday and lasting through Thursday morning. It does look like the heaviest rain may remain just to our south. This is where rainfall totals between 1-3 inches will be possible. To the north, and for most of northern Illinois, rainfall amounts between half an inch to an inch will be possible.

Rain chances remain following Tuesday's beneficial rainfall

Beneficial Rain:

Beneficial rainfall made its way across much of the Stateline on Tuesday, providing a welcome boost to an area that has seen its fair share of warm and dry conditions during the summer months. Some locales picked up more than 1.25" of rain. In Rockford, the rain gauge saw a steady climb throughout the day, ultimately finishing with 0.77".  

Shower Chances Remain:

Rain chances do not completely disappear behind Tuesday's rainfall, though they will be more limited moving forward. The best opportunity for showers today will be south of I-88, where the front boundary responsible for yesterday rain resides. Areas closer to the Illinois/Wisconsin border may see little to no rain, though an isolated shower can't be ruled out. With clouds sticking around and a cool easterly wind in place, expect highs in the low 70s. 

Rain chances tick up slightly once again overnight, bringing the potential for scattered showers and an isolated thunderstorm or two. Even then, the more favorable setup for rain will remain tied to the front parked to the south of the area. Overnight lows will be a touch warmer in the low 60s.