It's been a dramatic flip in the pattern across northern Illinois this month. We went from soaking rain in April - ranking as the 7th wettest on record - to a notably dry stretch here in May, which is now running as the 4th driest on record so far. The shift has been so significant that portions of northern Illinois are now classified as abnormally dry according to the latest edition of the Drought Monitor.
Rain chances remain limited moving forward. We do have a couple of opportunities to squeeze out some rain - first with a few light showers late Friday into Friday night, and then again Saturday evening into the early stages of Sunday morning.
Even with those windows, this won't be even close to a washout as a ridge of high pressure begins to build aloft, limiting widespread coverage and duration. City Market weather should cooperate, just with a bit more cloud cover overhead. Skies are expected to remain mostly cloudy throughout the event, but conditions will stay dry and comfortable. Temperatures will start off right near the 70-degree mark, then gradually easing back into the low 60s.
Warm Memorial Day:
From there, expect temperatures to climb back above-average over the holiday weekend. Afternoon highs will top out in the low 70s Saturday, upper 70s on Sunday, and then low 80s Monday. With a ridge of high pressure in control aloft, we can expect these 80-degree temperatures to carry on well into the next week, at least into Wednesday.
After one of the wettest Aprils on record, May has been the exact opposite. Warm and dry days have been far more common over the last few weeks. Through the first three weeks of May, the Rockford airport has only received 0.28" of measurable rainfall. Not only is that nearly 2.5" below average, but it is also the driest start to the month since 1992. If we do not accrue a full inch of rain by the end of the month, it will go down as a top 3 driest May on record.
It took a while to dig out of the drought conditions that we carried over from last fall. But since all the drought conditions had been removed back in early April, it only took a few weeks of a dry May to bring abnormally dry contour back into the region. Last week, only about 12% of the state was experiencing abnormally dry conditions. This week, that percentage is more than double, above 24%. The moderate and severe drought in Southern Illinois did not see any change from last week to this week.
But will we see any widespread rain anytime soon? The answer is probably not, as we are beginning to see more summer-like patterns in the atmosphere. The upper levels in particular are set to reach into a blocking pattern with dueling lows on either side of the country. That will force a warm and drier air mass across the Central third of the county, limiting overall rainfall potential.
While it is not totally dry, the rainfall we may see will not amount to much. More soaking rains may be possible South and well West of the area, but much of Illinois/Wisconsin will be removed from the highest rainfall potential over the next 5-7 days. Unfortunately, with more warmth on the way, that could lead to more developing drought conditions.
May has delivered a mixed bag in the Stateline so far, with a noticeable tug-of-war between spring chill and early-summer warmth. Out of the first 20 days of the month, we've logged only 4 days stuck in the 50s and five days stick in the 60s, highlighting some of those cooler, cloudier stretches. But warmer air has made its presence known - 11 days have climbed above the 70-degree mark, giving the month a mild and at times summer-like feel despite those dips.
Cooler Stretch Continues:
Looking ahead, it looks like those occasional dips will win out prior to Memorial Day as cloud cover works its way back into the Stateline. We'll especially notice that on Friday with thicker clouds limiting sunshine and keeping temperatures in check. Afternoon highs will hold in the low to mid 60s. Winds will also have a say as they will be out of the east-northeast today, then out of the east on Friday.
Holiday Weekend Surge:
Fortunately, a much warmer pattern sets up for the holiday weekend. Temperatures will surge thanks to a strengthening ridge of high pressure building in aloft in the atmosphere. This displaces the jet stream far to the north, placing it across southern Canada.
This type of setup will promote more sunshine as well as a steady warm-up, allowing afternoon highs to climb back into the 70s this weekend, and even the low 80s for Memorial Day and next week. Along with this ridge comes limited rain chances and extremely low severe weather potential.
After a chilly start Wednesday morning temperatures have warmed nicely for the afternoon, reaching the low to mid 60s. It has been a little cooler, however, for areas east of Belvidere and DeKalb where a lake breeze has kept temperatures in the 50s. The cooler air will begin to shift further inland over the next few hours, bringing temperatures down into the 50s for most between 7pm and 9pm.
Skies are mostly clear for now, but cloud cover will slowly increase from the west as a few little upper-level disturbances move in from the central Plains. While there is an increase in moisture with these disturbances, dry air from high pressure over the northern Great Lakes will limit most of the incoming moisture. This will leave us with a mostly cloudy sky later tonight and into the afternoon Thursday. As a result, temperatures will only warm into the low to mid 60s.
The Stateline has been riding a stretch of beautiful, earlysummer-like warmth over the past few days, with afternoon highs peaking in the upper 70s and low 80s. But as is often the case this time of year, that warmth won't remain consistent. A cold front that swept through Tuesday has snatched that warmth away, setting the stage for a noticeably cooler stretch before Memorial Day weekend.
Today starts on a much cooler note, with temperatures dipping in the low to mid 40s. That cooler air sticks around through the day, with afternoon highs only topping out in the low to mid 60s. Again, much cooler than your typically late-May standards. While it will feel noticeably different compared to the past two days, high pressure moving through will at least keep conditions pleasant with plenty of sun. We'll mix in a few clouds during the afternoon.
Showers Return Friday:
We'll keep that cooler, quiet pattern into Thursday, with afternoon highs once again settling in the low 60s under a mix of clouds and sun. By Friday, highs may trend cooler as an easterly wind sets up, helping pull in more cloud cover and even the chance for a few passing showers. That added cloudinessand onshore flow will keep afternoon highs limited to the low 60s, round out a noticeably cooler end to the work week across northern Illinois.
For the second morning in a row, northern Illinois is waking up to the leftovers of a severe weather event that originated in the central plains. A few showers, and even an isolated thunderstorm will be possible as a strong cold front pushes through.
Clouds will hang tough through much of the day as a cold front gradually pushes across the region, keeping skies mostly overcast for the time being. As we head deeper into the afternoon, however, we should begin to see some breaks in those clouds. Temperature will respond accordingly, settling into the low 70s for highs. Behind the front, a shift to the northwest wind will usher in a cooler air mass, and that will become more noticeably this evening and overnight tonight as low temperatures aims for the mid 40s.
Staying Cool:
A northeast wind take control on Wednesday, helping to keep temperatures running below average with struggling to climb out of the low 60s. Thatcooler flow will be paired with a partly cloudy sky as high pressure slides in from the northwest. Highs aims to remain in the low 60s for Thursday.
Tuesday will bring a cold front with a few stray showers pushing through during the early part of the day. Temperatures will fall over the course of the day, reaching the 40s by Wednesday morning. High pressure overhead will ease up the winds but also result in a cooler air mass overhead.
Humidity will fall away rather quickly behind the front. Dew point temperatures will fall below 50 degrees by Wednesday afternoon and not rise back above that mark until later Friday. Eventually, a small tug of moisture will return over the weekend with a smaller chance for some showers on occasion. Air temperatures will only rebound to the mid-60s with a pleasantly cool feel both Wednesday and Thursday.
Skies have been dry, but mostly cloudy, for much of our Monday afternoon following showers and thunderstorms earlier this morning. Most of the severe weather remained south of the immediate Stateline, with ongoing severe storms over eastern Michigan. Non-severe showers and thunderstorms have been ongoing downstate.
Conditions will remain mostly dry through the rest of the afternoon and early evening as ongoing severe weather continues across the central Plains. There, numerous severe thunderstorm and tornado warnings have been issued.
The expectation is for those storms to remain well to our west through the evening, forming into a line of storms as they move into western and central Iowa between 9pm and 11pm. Severe weather will still be possible west of the Mississippi River through the late evening, but instability does weaken a bit to the east.
An increasing low-level jet, stronger winds in the lower levels of the atmosphere, will likely help support at least some strength of the thunderstorms through the night, but the strongest of the storms may end up just to our south after Midnight. In fact, there are a few of our forecast models that have the northern edge of the line breaking apart by the time it reaches northern Illinois and southern Wisconsin.
If the northern extent of the line holds together, we should see showers and thunderstorms move in around Midnight, most likely between 1am and 2am. There should be an overall weakening trend but there is a low-end chance for a stronger wind gust or two. This would occur if the line holds together. If it doesn't then the chance for those stronger wind gusts would decrease quite a bit.
We've tracking the leftovers from yesterday's intense severe threat across the plains. The good news is that most of this activity is expected to remain under severe limits, but we are keeping a close eye on one particular storm. The National Weather Service has issued a Special Weather Statement for this cell as it moves into southwest Carroll County. As it tracks to the northeast, it could bring wind gusts up to 40 mph and pockets of small-sized hail.
Monday's Severe Threat:
We're not done yet unfortunately as another chance for strong to severe storms arrives tonight into Tuesday morning. Once this morning's activity clears out, the rest of Monday actually looks dry and warm with highs peaking in the low 80s.
The Storm Prediction Center has the highest risk for severe weather well to our south and west over areas in Kansas, Nebraska, and Missouri. As those storms organize and move east, we'll likely see a similar setup to last night, where storms gradually weaken on approach but still holding together enough to track through after midnight, with a least a chance for a few t-storms into Tuesday's morning commute. Gusty winds and small-sized hail will be the primary concern with any severe thunderstorm but again, instability or storm fuel remains quite as these storms move in from the west.
Cooling Back Down:
Temperature-wise, this incoming cold front will be strong, bringing a noticeable shift in our temperatures as we approach the middle of the work week. After enjoying afternoon highs in the low 80s, we'll take a step back into the 70s tomorrow, followed by a much cooler feel by midweek with highs settling in the 60s for Wednesday. It's a sharp reminder that even as we get a taste of summer warmth, spring can still deliver some quick and noticeable cool-downs!
Widespread severe weather is not expected, but some pockets of the storms could pack a punch. There are a few windows for storms over the next 36 hours, primarily during the overnight windows. Late tonight, storms will arrive from the West primarily after 2AM on a weakening trend but could bring some gusty winds and hail threats. Monday morning may have some carry-over storms from the nighttime window, with some intensification possible as daytime heating builds in. Most of Monday afternoon should end up dry, with another widespread round of storms arriving late Monday evening into the night.
The nighttime arrival of storms will be unfavorable for widespread severe weather, but storms look to hold together some of their strength as they approach the area well after midnight. Storms could arrive for Northwestern Illinois as early as 1-2AM and may be near the I-39 corridor around 4AM. While widespread severe weather is not expected due to the unfavorable diurnal timing, a few pockets of storms may pose a wind/hail risk. If storms maintain a bow echo shape, an isolated tornado cannot be ruled out either.
Those morning storms may linger later into mid-day, especially across Central Illinois. As daytime heating builds in, there may be some strengthening of those storms with another threat for damaging winds and hail. Most of the afternoon will end up dry, but an isolated storm may be possible with high levels of instability building in.
The main wave for Monday will again arrive much later in the evening/night. This time around, storms may arrive around 12AM Tuesday for some of the Western Counties, then push through the rest of the area into the pre-dawn hours of Tuesday. Storms will be in a weakening trend once again, but severe threats may be maintained a bit longer into Tuesday morning compared to Monday mornings risk with a bit stronger low-level winds supporting the line.
Both tonight and tomorrow night will feature scattered storms, with varying trends of severe weather risk. It will largely depend on how much storms are able to maintain their strength as they trek across Iowa into the late evening. Much of the Stateline is under a Level 1/5 Marginal Risk for Sunday night and a Level 2/5 Slight risk for Monday afternoon/night from the Storm Prediction Center outlooks. Be sure to have multiple ways to get warnings the next few nights, including ways to wake you up if a warning were to come in the middle of the night!
A few isolated to storms may begin the day Sunday, but the afternoon will dry out and warm up once again. High temperatures will likely push well into the 80s, similar to if not warmer than Saturday. Once again like Saturday afternoon, the humidity will fuel a lot of storm energy. But storms are unlikely after mid-morning with a lack of a trigger mechanism to initiate storms. Some shower and storm activity is possible to the North along a warm front.
While the afternoon will remain dry, it will be rather humid with dew point temperatures pushing the low to mid-60s: similar to if not a little higher than Saturday. Winds will increase feeding into the aforementioned warm front, with some Southerly gusts pushing 30 mph at times through the day.
Better coverage of rain and storm potential will arrive toward Monday morning. A few of these storms may pose a risk for gusty winds and small hail, but the severe threat early in the morning should be somewhat limited.
Monday afternoon could be a different story, however. Following that morning round of storms, the atmosphere could become primed for more storms with high levels of instability once again. But very similar to Saturday and Sunday, the atmosphere is lacking a trigger mechanism. Storm development during the afternoon will hinge heavily on that forcing (or lack thereof) and how morning storms evolve. Stay tuned!
With as warm and humid of a day it has been, we have remained remarkably dry. This despite a lot of uncapped instability, or storm energy, sitting overhead, fueled by the humidity at the surface. Usually, with an uncapped environment, you would see several storms develop using up all of this fuel.
But moisture and instability are just two ingredients for storm development. Storms also need something to jumpstart the process with a boundary or lifting mechanism along with wind shear to keeps the storms going. We do not have strong lift or shear right now, which is why we have remained dry so far Saturday evening.
But an outflow boundary/weak frontal boundary is sitting nearby with all that instability. That boundary may provide just enough of a trigger to get some isolated thunderstorm development between now and 12AM. Any storm that fully develops may pose a risk for gusty winds and some small hail, but the severe threat is not very high.
Slightly higher coverage of showers and storms may be possible after 12AM, with isolated to scattered activity carrying over into Sunday morning. The severe threat does not appear to be very high with the overnight storms, either. A large majority of the area will likely remain dry through at least most of the night.
Thunderstorm chances persist through much of the weekend, but there will be many dry hours between waves of showers and storms. The outflow boundary from Friday night's storms will be a potential focal point for additional showers and storms Saturday afternoon. The large majority of the area and time will remain dry, but an isolated storm or two remain possible through the day. Higher coverage of storms may be possible toward Saturday evening/night.
The Storm Prediction Center has maintained their Level 1/5 Marginal Risk for severe weather, indicating one or two storms may reach near severe limits. Limited forcing and shear will prevent more widespread and organized severe potential during the daytime. Better organization looks possible with the evening wave.
Another threat for severe weather exists Sunday. This will be more of a "watch and see" event compared to Saturday, as it depends on how Saturday night's storms evolve. Similar to Saturday, the large majority of Sunday should be dry, but any storms that develop from the West may pose a risk for severe weather as they progress East across the area. This may be another late evening risk, like Friday night.
Both days this weekend will be very summer-like with warm and even humid conditions. Afternoon highs will push into the mid-80s. Isolated storms remain possible each day, but both afternoons appear to be relatively dry compared to the evening/nighttime windows.
[2:00AM] Round 1 of storms is now exiting the area, leaving some gusty outflow winds (30-40 mph) in its wake. Round 2 is developing in Eastern Iowa and will move toward the Stateline after 4AM. While widespread severe weather is not expected behind round 1's outflow, some isolated pockets of stronger thunderstorm winds may be possible toward daybreak.
[1:30AM] Along and behind the outflow boundary from the storms, winds have been gusting near 25-35 mph in some spots. While it may remain breezy through the night, the severe weather threat is ending for our Western Counties.
[1:25AM] While not severe, this storm in Central Boone County has perked up a little and may be capable of producing penny to nickel sized hail as it moves Northeast at around 40-45 mph. Poplar Grove, Capron, Chemung, and Harvard may experience some hail with this storm.
[1:15AM] This storm centered over West Rockford has been able to produce at least pea sized hail and very heavy rain over short bursts. Storm is not severe at this time, but is moving Northeast at around 45 mph.
[1:00AM] The Monroe airport measured a wind gust of 47 mph as storms passed through. A severe thunderstorm warning remains in effect until 1:30AM for Green and Rock Counties with 60 mph wind gusts possible.
[12:25AM] A severe thunderstorm warning has been issued for Green and Western Rock Counties in Southern Wisconsin until 1:30AM. These storms are capable of producing 60 mph wind gusts and penny sized hail as they move East at 60 mph. A tornado is also possible, but not imminent at this time.
[12:15AM UPDATE] Storms have moved into SW Wisconsin with a few areas of rotation and associated tornado warnings. Storms are generally moving East at around 30 mph. Additional cells have begun producing lightning in NW Illinois in a more isolated fashion. Weakening trends will continue with Eastward extent, but it is unclear how quickly they will weaken. Right now, the highest chance for anything severe over the next few hours is primarily across Southern Wisconsin, but far Northern Illinois may get clipped by a strong storm or two. Highest threats will remain with damaging wind gusts, followed by very isolated spin-up tornadoes, then small hail.
[10:45PM UPDATE] A severe thunderstorm watch has been issued for Northwestern parts of the Stateline until 5AM Saturday. Storms out in Iowa have been holding together to an extent as they move East with a few severe warnings along the line. Primary threats would be damaging wind gusts and some instances of small hail. Our primary storm window will be through 2-3AM, exiting East after 3-4AM.
Scattered storms have developed in Iowa with several severe thunderstorm warnings. This line of storms will continue to progress Eastward, reaching NW Illinois after 10-11PM. Storms will be on a weakening trend but could still produce some damaging wind gusts and hail.
The current late evening SPC outlook has expanded the Level 2/5 Slight risk further East across a large portion of the Stateline now. Storms will be possible from 11PM-3AM, so be sure to have ways to get warnings should any be issued that late!
