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.
