High and dry early this week, increasing humidity by weekend

 [6:20PM] While most of the area will be dry this evening, a few very isolated sprinkles may be able to work through some drier air through the night. The rainfall will not amount to much. Only a few hundredths of an inch may come down for those who do see any rain.

Pending we don't see any measurable rainfall before midnight, this May will go down as the driest on record for Rockford. Only 0.47" of rain fell this entire month at the airport, compared to the average 4.18" rainfall we typically see in May. Especially remarkable given how long ago some of the other top 5 have been!

A tiny bit of moisture may produce few sprinkles from time to time from late evening through the overnight hours, but most of the area will remain dry at any given time. Whatever rain does fall probably will not amount to much, likely less than a tenth of an inch for those who do see rain.

Another round of dry high pressure will then take hold early in the week, bringing pleasant afternoons and cooler nights. Monday and Tuesday night could feature lows nearing the upper 40s in a few locations!

But the lack of humidity will not last for long. As that area of high pressure slides away, surface winds will turn to come from the Southwest. That will bring an increase in moisture, especially at the surface. Dew points will likely climb into the 60s by Friday evening. A more unsettled pattern will develop as a result, with at least isolated chances for some showers and storms beginning Thursday night. While it may not be a soaking rainfall for everyone, prospects for much-needed rainfall look a little better through the first week and half of June.

Subtle pattern change may bring slim rain chances late next week

 While we have been stuck in the warm and dry pattern lately, subtle changes may be on the horizon. The large scale upper level ridge has been a dominant feature for our weather pattern, bringing surface high pressure systems, a dry Easterly wind, and very little rainfall over the last week or two.

That ridge will begin to break down late into the week, resulting in at least a few slim chances for rain starting Friday. Increased jet stream flow overhead will result in increased moisture and subtle waves that are able to precipitate some of that moisture out as rain.

Unfortunately, it probably won't be the widespread and soaking rain that we need, but anything helps at this point. Coverage of rainfall may not reach much higher than 30-40% at any time Thursday night through the weekend, but at least some locations in the Stateline will have a shot at some rainfall, though others may end up staying dry. It's not much, but it's a start!

Warm and dry, but pleasant this weekend

 It feels like a broken record saying this, but we have more of the warm and dry pattern to come. At least for the weekend that means pleasantly warm days and cooler nights! Afternoon highs will push near or above 80 degrees both Saturday and Sunday with overnight lows in the low/mid 50s.

The one feature of note this weekend will be a lake-enhanced backdoor cold front pushing in off Lake Michigan. This will bring stronger winds from the East during the day gusting near 25 mph at times. Another impact that front will have is the substantially cooler evening, especially for Eastern parts of the Stateline. Temperatures will quickly fall back into the 50s, so any outdoor plans you have may start turning a little cool by 7-9PM.

"Rapid Onset Drought" possible as dry conditions continue across the Stateline

 Written By: First Warn Weather Intern Patrick Murray

The Climate Prediction Center has highlighted the entire Stateline region under a risk for what they're calling a "Rapid Onset Drought". A rapid onset drought (also called a "flash drought") happens when abnormally low precipitation amounts are coupled with abnormally high temperatures.

Typically, we don't see our first 90 degree day until June 4th. The past month has included many days with above normal temperatures. This year, we saw our first 90 degree day on May 27th, a full week early.

This is all thanks to high pressure which has been sitting over the Great Lakes region for the past few days. This area of high pressure will slowly shift east as an overall pattern change takes shape, but this likely won't happen until well into the next week.

The current drought monitor from the CPC (valid as of Tuesday) highlights almost the entire Stateline region under the "abnormally dry" category. While we aren't technically in a drought as of now, we will likely see one develop over the course of the next week or so.

Our next decent chance for rain doesn't appear in the forecast until Friday (6/5). There is a slight chance for an isolated shower or thunderstorm on Monday (6/1) and Thursday night (6/4), but overall, we look to stay very dry.

Warm and dry weather causes abnormally dry conditions to expand in northern Illinois

 

It should come as no surprise that the abnormally dry conditions have expanded across northern Illinois and southern Wisconsin following a very warm and dry stretch of weather. The latest drought monitor from the National Drought Mitigation Center shows the drier than normal conditions expanding from where they were just last week, to now covering the majority of northern Illinois and southern Wisconsin.

This follows what has been an exceptionally dry May with only 0.47 inches of precipitation being recorded at the Rockford Airport. Month to date the May precipitation is 3.25 inches BELOW where it should be. And with only a few days left of the month our chances for precipitation look to remain very low! Month to date we are the driest on record, and this month will likely be the driest May on record since record keeping began in 1905.

The pattern may start to change after the first week, to week and a half of June as the blocking ridge that has been in place starts to break down. This may allow a few more storm systems to move through giving us at least a little better chance for some precipitation. Although, our warmth looks to be sticking around.

Temperatures hit 90 degrees for the first time this season Wednesday afternoon

 

Phew! It was a toasty one this afternoon with temperatures warming into the upper 80s and low 90s. Rockford reached its warmest temperature so far this season with a high of 91 degrees! The record high for May 27th is 99, which was set back in 2012. The low this morning fell to 52.

Skies have been mostly sunny for much of the afternoon with only a few cumulus clouds bubbling up over the last few hours. Those clouds have formed with the little instability we have overhead but are beginning to quickly fade this evening. Temperatures will remain in the 80s through sunset but are expected to quickly drop following the passage of a back-door cold front this evening. Overnight lows will once again drop into the low to mid 50s.

Thunderstorms have developed along the cold front to our north in Wisconsin but will really lose steam as they travel closer to southern Wisconsin after 7pm/8pm. There is a small chance for an isolated shower or storm in southern Wisconsin, but the vast majority of the viewing area is expected to remain dry.

On average, our first 90 degree day is usually reached around June 4th. Last year the mercury reached 90 degrees on May 15th. Our earliest recorded 90 degree day occurred on April 10th back in 1930, and our latest was in 2008 when we didn't reach 90 degrees until September 1st. This will likely be our only 90 degree day through the rest of May as temperatures are expected to remain in the 70s and 80s through the weekend and into the beginning of June.

Dry weather to persist, a few slight chances of rain

 Written by: First Warn Weather Intern Patrick Murray

Overall, dry weather will continue to dominate the forecast to end the month of May, and the beginning of June doesn't look to tell much of a different story. An Omega block has settled in across the central US, with high pressure in place preventing any storm system from reaching the area.

High pressure is expected to be in place across the Great Lakes region next week. As this area of high pressure slowly pushes off to the east, and we find ourselves on the western edge of a disturbance centered over the northeast, multiple back-door cold fronts will make their way through the Stateline.

The first looks to arrive Thursday afternoon/evening, with weak forcing and upper-level winds in place, rain looks unlikely, though temperatures will cool nicely into the end of the week.

Another cold front approaches the area Saturday night into Sunday, with high pressure in place over the area, limited moisture will be in place, meaning most, if not all of the area, stays dry.

The final of this parade of back-door cold fronts moves in Monday evening. Slightly better dynamics will be in place for this one. Despite this, rain chances still remain very slim. Most of us will stay dry, though a few of us could see an isolated shower and perhaps even a rumble of thunder thanks to some instability aloft.

So, what exactly is a back-door cold front? Typically, cold fronts move in from the west/northwest and are associated with an area of surface low pressure. Back-door cold fronts, on the other hand, come from the east/northeast (or the "back-door" if you will) and are often associated with breezes off of Lake Michigan. Usually, we monitor these back-door fronts for the potential for some shower and thunderstorm activity, but the dynamics in place over the next week, and strong high pressure will likely prevent most of us from seeing any rain, meaning the end of May and beginning of June promise to be drier than what we are accustomed to.

Summer like conditions to round out the month

 

May has certainly been on the warmer side with temperatures as we've already seen more than half the days this month with temperatures above average! This doesn't look to change as we head towards the month as high pressure will looks to keep us above average through the rest of May!

Starting with today with high pressure moving to our east today, winds will gradually shift southward allowing for warmer temperatures to creep up into the region. Today as well as tomorrow could be the warmest days not only of the month, but the entire year so far as plenty of sunshine both days should bring us into the upper 80's.

Through the evening tomorrow a weak cold front is expected to move through the state line which may bring an isolated sprinkle or two to some of us. However, the biggest impact will be sending our temperatures down into the 70's towards the end of the week. Thankfully, our upper-level pattern will continue our very warm pattern with upper-level ridging developing, on the flip side though this will also keep us very dry heading into June. As we round out the month, precipitation probabilities may need to be monitored quite heavily as this year's May might be one for the record books in terms of record low precipitation. 

What is an upper-level blocking pattern?

 The last week of May will feel more summer-like as temperatures climb into the mid and upper 80s Tuesday and Wednesday, and then in the upper 70s/80s for the rest of the week. The warmup, the result of an upper-level blocking pattern that'll hold strong through the weekend. You've likely heard us talk about blocking patterns, but what exactly are they?

An upper-level blocking pattern occurs when either high pressure or low pressure develop over an area, preventing other weather systems from moving through - hence a block. Blocking patterns can last for several days which can often result in a persistent weather pattern for those locations that end up under the block. For example, blocking high pressure in the summer months can lead to warm -or hot- and dry conditions for many days in a row. There are several blocking patterns that can occur, but the two meteorologists often reference the most are the omega block and rex block.

Omega Block:

An omega block often occurs in the summer and is responsible for hot and dry conditions that tend to lead to heat waves as precipitation usually occurs around the outer edges of the blocking high. This blocking pattern gets its name because it resembles the Greek letter Ω.

The higher pressure aloft will cause the air to sink, warming temperatures near the surface. The sinking motion also prevents any air from rising, limiting the chance for any precipitation to develop underneath the ridge. This is why these types of blocking patterns can worsen drought conditions, while at the same time cause temperatures to soar. Often times heat and drought will go hand-in-hand. Overtime, the blocking pattern will start to break down as smaller scale disturbances move over top of the ridge, causing it to weaken and eventually breaking it down.

Rex Block:

Rex blocks occur when high-pressure becomes locked in place from low-pressure to the south. The cut-off nature of the low prevents the high from moving and typically the jet stream winds to the west are not strong enough to initially move the high itself. These types of patterns will hold until one of the pressure systems changes intensity, causing the high and low to become unbalanced.

Dry conditions can be found near the blocking high while an unsettled pattern will occur near the low. 

Memorial Day forecast: Morning clouds give way to afternoon sunshine

 Radar may look a little daunting early this morning, but showers will dissipate by the time they arrive. There is a very small chance (10%) for a stray shower Northwest of Rockford through 11AM, but sunshine is expected by the afternoon.

That sunshine will result in a jump in temperatures. Afternoon highs will push into the mid-80s for most. Game on for any outdoor plans, including any parades, cookouts, and other festivities. Remember to apply sunscreen and hydrate today as it will be a warm day!

Summer-like week with rain chances few and far between

 While some locations got a bit of rainfall last night into the early hours of this morning, it wasn't for everyone. A few spots across Lee/DeKalb Counties saw between 0.5-1.0" of rain, but the Rockford airport only picked up 0.19", bringing the monthly total to 0.47", the 3rd driest May to date.

No rain expected for your Memorial Day plans, but a few clouds will pass by midday. Those clouds will not limit the degree of warming whatsoever, as afternoon highs still push into the mid-80s. A+ for any outdoor plans!

Unfortunately, it does not look like we have much rain on the way with a blocking high pressure that will set up near the Great Lakes, limiting rainfall potential locally through the week ahead. Soaking rain may be likely as close as Southern Illinois, but the dry air from Great Lakes high pressure will severely limit Northward extend of that moisture, resulting in very little if any widespread rainfall over the next 5-7 days.

On the bright side, that drier weather will lead to a few more days in the mid-80s for afternoon highs. A backdoor cold front Wednesday may produce our only isolated rain chance, but also will work to bring a "cooler" Easterly wind with highs back to the upper 70s to close out the week.

Warm and dry to close out Memorial Day weekend

 After a few light showers Saturday night, the remainder of the holiday weekend will be dry with a continually warmer trend. The overnight rain will be exiting to the East by early Sunday morning. Southeastern parts of the Stateline such as Rochelle and DeKalb may hold onto a slim chance for light rain through 7AM, but mid-morning into afternoon will bring a decrease in clouds, drying things out.

Temperatures Sunday afternoon will approach or surpass the 80-degree mark with more abundant sunshine after midday. Evening and overnight will not be very cool, only seeing lows drop into the mid-50s. Monday will bring another step up in the temperature department, despite some afternoon cloud cover. Mid-80s appear likely, and without any rain, Monday will be a picture-perfect unofficial start to the summer season for any outdoor activities that may be in the plans.

Radar Monday morning may look a little daunting with some showers to the Northwest, but we should see those decay as they approach by midday, resulting in only a few passing clouds locally. The chance for any rain is under 10%. Once the clouds pass by 5PM, the evening and nighttime will be clear once again.

Isolated showers possible Saturday evening, non-zero lightning threat

 [11PM] Isolated showers persist, mainly along the I-39 corridor. While most will remain dry through the night, a brief period of light rain may be possible where these showers pass overhead. A rumble of thunder may also be possible, as a couple lightning strikes were detected in Bureau County near Walnut, IL. Showers are slowly moving to the Northeast at 10-25 mph. Any lingering showers give way to mid-day sunshine tomorrow.

[8PM] Two main areas of light showers in the Stateline. One pocket is right along the state line between Broadhead, WI and Ridott, IL and another pocket is in Southern Lee County. Both areas of light showers are moving Northeast at only 10-20 mph. A brief shower will be possible ahead of these cells, but many will remain dry this evening.

Heads up to anyone participating in outdoor festivities this evening! A few *very* isolated showers have begun developing West of I-39 and will slowly track East later tonight. Brief downpours and even an isolated bolt of lightning remain possible, but the majority of the area will remain dry at any given time.

Light showers may be possible through the early part of the night, but coverage will likely not reach higher than 30% at any given time. Temperatures will remain mild, with lows only dropping into the 50s.

Weekend largely dry and warm, but isolated showers remain possible Saturday

 The upcoming Memorial Day weekend will be largely dry and warm, but an isolated shower cannot be completely ruled out Saturday. Outside of that, dry conditions are expected for both Sunday and Monday, including high temperatures pushing into the upper 70s Sunday and near the mid-80s Monday!

A weak cold front pushing through the area will be the driver behind the stray showers Saturday. The afternoon will end up dry before isolated rain may be possible from 4-11PM across the area. Most of the region will be dry at any given time with only about 20% coverage of rainfall, but a few raindrops may need to be dodged from time to time. An isolated rumble of thunder may also be possible but is not likely.

Limited rainfall coverage will remain a going trend over the next several days with a lack of widespread forcing to produce larger rain events. While a few showers may be possible Saturday evening/night, we will likely end up dry Sunday and Monday before more isolated chances return Tuesday into Wednesday. Whatever rain does fall will not amount to much, with most of the area likely seeing little to no measurable rain through Tuesday.

Dry pattern holds as temps climb towards Memorial Day

Drought Conditions Return:

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.  

Drought conditions return as dry stretch persists into late May

 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.

Cool now, summer later: Memorial Day warmth on the way

Monthly Recap:

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.