Widespread fog early Friday, summer-like weekend ahead

Dense Fog Advisory:

If you plan to travel this morning, please make sure to give yourself extra travel time. 

A dense fog advisory is now in effect until 9AM for Stephenson, Ogle, Lee, Winnebago, Boone, Dekalb, and McHenry County as well as Green, Rock, and Walworth County up in S. Wisconsin. Visibility has dropped to a half mile or less for a few. 

By late morning, fog won't be an issue. Skies will slowly clear throughout the afternoon, resulting in increasing sunshine. That, along with today's light wind out of the south and southeast will push temperatures into the upper 60s. High pressure will keep skies quiet overnight, with temperatures falling back into the upper 50s.

World War II Days:

As we've been hinting at, temperatures aren't going to feel very fall-like for the first weekend of fall. A much warmer air mass spilling into the Midwest will help bring us back into the low 80s Saturday and Sunday. This is extremely good news for those who plan to attend World War II Days at Midway Village. In fact, the ridge responsible for this warm up will remain intact into early next week, leaving highs unseasonably warm for Monday and Tuesday.

Some improvement in drought conditions

 

The latest drought monitor shows some improvement in overall drought conditions occurring across Illinois and Wisconsin, with some of the higher improvements taking place in Wisconsin.

What may have seemed like a never-ending rain event for some, for others it wasn't enough. Regardless, some improvements did occur throughout the state of Illinois from last week to this week. Northern Illinois is still dealing with either moderate or severe drought conditions, but heavy rainfall over northeast Illinois has eliminated the drought in that area.

Wisconsin has had the most improvement, but there are still some locations that are dealing with severe and extreme drought conditions. The exceptional drought conditions there were observed over southwest Wisconsin have been eliminated, at least with the latest monitor release. But extreme drought conditions remain.

We are about to enter into a drier stretch of weather once again, the exception being northern Wisconsin where showers are likely into the weekend. For Rockford, and most of the Stateline, sunshine and warm conditions will take us into next week as high temperatures reach the low 80s.

The month of September will go down in the record books as a dry month, receiving only 2.19 inches of rain. As of Thursday evening, this puts us at a 1.24-inch deficit. Looking back to January 1st the deficit stands at just over six inches, which will grow through the beginning of October as dry conditions are in the forecast. The next chance for rain looks to return late next week, into next weekend.

Widespread fog possible early Friday

 

Mostly cloudy skies will take us through the rest of Thursday evening before gradual clearing takes place overnight. Despite the cloud cover, temperatures were still able to reach the low 70s. Under a partly cloudy to mostly clear sky Thursday night overnight lows will dip into the low to mid 50s. Calm winds, clear skies, and plenty of moisture from the recent rain will allow fog to form through the night.

The fog may reach its thickest point just before sunrise Friday, improving slowly through 9am. Skies should then turn partly cloudy with temperatures quickly warming into the middle 70s by the afternoon.

If the current cloud cover doesn't clear out as fast, fog coverage will be limited and may not be quite as dense. Either way, be sure to plan accordingly for the commute Friday morning.

Weather pattern dries out, multiple 80° days ahead

Trending Drier:

The streak carries on! Wednesday became the 12th consecutive day where the Rockford Airport observed at least a trace of rain. 9 of which have come in with measurable rainfall. This streak however should come to an end today as the stubborn low responsible for this week's rainfall pushes east.

 

Thursday begins with quite a bit cloud cover and even some patchy dense fog. But as the lingering effects of this recent storm system wear off, the expectation is that more sun will appear as the day progresses. 

The additional sunshine however won't have much of an impact on temperatures. With a cool northeasterly wind in place, highs will peak in the low 70s this afternoon. Skies will continue to clear into tonight, setting the stage once again for patchy dense fog for the morning commute Friday. 

Summer Isn't Done:

From there, sunshine will then name of the game for Friday as well as for the first weekend of fall. But thanks to a strong blocking ridge of high pressure aloft, temperatures this weekend won't be feeling very "fall-like". It's underneath this dome of high pressure where unseasonably warm air will spill across the Midwest and the Great Lakes. 

This will allow highs to peak in the upper 70s Friday, with 80° weather moving in Saturday. It's not until the middle of next week where we see this ridge begin to break down, allowing temperatures to somewhat cool. But it's also during this time in which our next rain chance swings in.

Lingering showers Wednesday, temperatures warm into the weekend

Lingering Showers:

Yesterday was the 11th day in a row in which the Rockford International Airport observed at least a trace of rain. Of those eleven days, eight have come in with measurable rainfall. 

Those that were able to get in on the more intense storms yesterday wound up with a whopping 4 to 6" of rain. To compare, that is how much rainfall Rockford would need to see to either significantly chop down or eliminate our annual rainfall deficit. Now, while a soaking rain event is not in the cards for Wednesday, this upper level low pressure system will give us one more opportunity for measurable rain before our weather pattern dries out. 

Wednesday will be a carbon copy of Tuesday, minus the risk for severe thunderstorms. Scattered showers and perhaps a thunderstorm or two will be possible at any given time of the day. 

When you factor in the cloud cover, the chance for scattered rain, and today's cool easterly wind, highs will struggle to climb out of the 60s. But if we manage to get in a few peeks of sunshine, then temperatures for a spot of two may briefly touch the low 70s. Any chance for rain should come to an end this evening, leaving us with a mostly cloudy overnight. Fog will also be a possibility into Thursday morning, with temperatures falling into the upper 50s. 

First Weekend of "Fall":

As we've been hinting at, a warming trend is set to take place starting Friday. Behind the departing low, a strengthening ridge will allow a warmer air mass to spread into the Midwest. 

Highs Friday and Saturday are ticketed for the upper 70s, with 80° weather in the works for Sunday and early next week. This coincides with the latest long-range outlooks issued by the Climate Prediction Center which has an 80-90% chance for above average temperatures next week. They also have a 70-80% chance for above-average temperatures as we approach next weekend. So Summer isn't giving up just yet!

Scattered heavy rain/storms Tuesday, brief tornado possible

Storm Chances Persist:

A slow-moving low and a stalled boundary were the main drivers into Monday's stormy end. While most storms remained below severe limits, one went on to produce a brief tornado near New Glarus and Belleville in northern Green County. As for Tuesday's forecast, same story, different day. With that cold core low swirling nearby, the opportunity for scattered storms continues as does the low potential for one or two of those storms to become severe.

Earlier this morning, the Storm Prediction Center put our areas south of the Stateline under a level 1 Marginal Risk for severe weather. This is mainly for the round that is slated to develop during the afternoon and evening. 

With high amounts of moisture in the atmosphere, heavy downpours remain a threat along with the risk for small hail. However, because of the added spin provided by this swirling area of low pressure, a brief funnel or tornado cannot be ruled out. The threat for strong to severe storms will lower significantly by sunset, but a few storms and heavy rainfall will remain possible overnight Tuesday and into the early stages of Wednesday. Highs will peak in the upper 60s and low 70s this afternoon, cooling into the upper 60s tomorrow. 

No So Fall-Like:

Once this nuisance of a storm system moves out, ridging to the west will slowly take control. This will not only allow our rain chances to significantly drop, but it will also help filter in a seasonably mild air mass. One in which will bring our temperatures back up towards the 80° mark by the weekend. Typically, our average highs should be falling into the upper 60s by the time we reach the month of October. Nope. That won't be the case this year.

Scattered storms and heavy rain continue through Wednesday

 

A stalled boundary draped across northwest Illinois and southwest Wisconsin Monday afternoon produced a few isolated thunderstorms. While the storms remained below severe limits, a few of the stronger ones did pose a risk for gusty winds and had torrential downpours - especially over parts of Stephenson and Jo Daviess counties.

Most of the storm activity through Monday evening will be confined to the northwest of Rockford, fading as we near sunset. Isolated showers and thunderstorms will remain possible overnight.

Temperatures Monday afternoon warmed into the middle to upper 70s thanks sunny skies, but cooler temperatures can be expected Tuesday and Wednesday with an increase in cloud cover. Highs on Tuesday will only warm to the low 70s, and then upper 60s and low 70s Wednesday.

Low pressure currently centered over central Minnesota will move closer to the Stateline Tuesday. As it does, thunderstorm activity will begin to
increase in coverage - first in the morning and then again during the afternoon and evening. With high amounts of moisture in the atmosphere, heavy downpours remain a threat along with the risk for hail. Funnel clouds may also occur with any of the stronger storms that occur. The colder temperatures aloft with the low will help increase instability and lift within the atmosphere. With the presence of a boundary under the low at the surface, low level wind shear will increase slightly, causing weak rotation with some of the stronger storms. If this occurs, funnel clouds may be possible. 

The threat for strong storms will end with sunset, but heavy rainfall will remain possible overnight Tuesday and into Wednesday. Over the next couple of days rainfall totals up to two inches could occur, with areas favored from far northern and northwest Illinois to southern Wisconsin to receive the highest totals. 

  

Isolated PM rain, chances carry on into Tuesday

Low Stays Put:

Remember that 'rex' blocking pattern we touched on last Friday? Well, a glimpse at upper-level maps this morning shows that it's still in place. However, the ridge over the Rocky Mountains has strengthened, lifting into northeast Canada. 

What this has done is trap the slow-moving occluded low over the Dakotas and Minnesota, leaving us in the perfect spot for early-week rain chances. 

Early Week Rain:

Both Monday and Tuesday feature the chance for hit-or-miss showers and thunderstorms. The keyword being "hit-or-miss", meaning not everyone will get in on the chance for rain. Still, I would make sure to pack the umbrella just in case. 

Temperature-wise, expect highs to peak in the low to mid 70s Monday, falling into the low 70s for Tuesday.  Severe weather will not be a concern. In their latest outlooks, the Storm Prediction Center has kept the entire Stateline under a "general"storm risk, meaning most if not all thunderstorms should remain under severe criteria. It's not until Wednesday night where this upper-level low phases out, allowing the ridge to the west take hold. This will not only help dry out our weather pattern, but also help filter a more milder air-mass for the first full weekend of fall!

First weekend of Fall features Summer-like warmth

 Fall officially started early Saturday morning but temperatures during the afternoon felt anything but fall-like as highs area-wide warmed into the low 80s. Sunday has been another warm Fall afternoon with temperatures inching back near 80 degrees, currently sitting at 80 degrees in Rockford as of 4pm.

A delay in both cloud cover and rain showers have been a big contributor to the warmth this afternoon as drier air has won over any precipitation that has tried

to develop. We will maintain a partly sunny sky through the rest of the afternoon with temperatures possibly warming another couple degrees over the next hour or two. A slow increase in moisture ahead of a rather slow moving upper-level low will help keep some cloud cover around Sunday night and the chance for a shower or two. But with little instability the prospects for anything widespread remains on the lower end.

Temperatures Monday *could* be lower than they were Sunday afternoon, but only if cloud cover increases. If we do end up seeing more sunshine than forecast, then highs could easily warm back into the upper 70s once again.

The upper low is, however, forecast to dip southeast across Iowa and Illinois late Monday night and Tuesday. With that we should see an increase in cloud cover and a better chance for rain and a few
thunderstorms lasting through Wednesday. Beyond Wednesday, temperatures are expected to warm once again, possibly reaching near 80 degrees to round out September and welcome in October. 

Rain lingers into early Friday, weekend trending drier

Rain Lingers:

The Stateline has had an opportunity for rain each and every day this week. This trend is likely going to carry on into our Friday as a weak and stubborn low pressure system sits close by. 

If you plan to step out the door this morning, be sure to have the umbrella with you. Rain chances will be best during the first half of the day in a scattered fashion, with conditions turning drier for the afternoon. If any late-day sunshine were to emerge, this will further help temperatures make the climb back into the upper 70s. Forecast models do bring a few passing showers through the area overnight, with temperatures falling back to 60°.

Drier Weekend:

Changes to the weekend forecast have more become apparent thanks to the influence a coastal system has on our atmosphere. To some, these changes will bring positive news. On the flip side, for those that want more rain, close your ears. 

At first, it looked like this somewhat active weather pattern was going to continue into the weekend. But potential tropical cyclone sixteen has thrown this weekend's rain chances a curveball as it helps develop what is known as a 'rex' block ridge of high pressure. This is an upper-level blocking pattern that features high pressure north of low pressure. With the development of this blocking pattern, this slows down the low to the west, lowering our chances for rain as we make the seasonal transition into Fall. That's right friends! Fall officially begins at 1:50AM CDT Saturday!

Expect sunshine to emerge in partial fashion for the first day of fall, with temperatures climbing to the 80° mark. As the associated frontal boundary approaches from the west, clouds will increase into Sunday. This will leave us with a mostly cloudy sky. That, along with a chilly wind off of Lake Michigan will make for highs in the low 70s. With ridging becoming the dominant upper-level feature, much of next week will be dry. In a similar fashion to Sunday, highs during this stretch will peak in the low 70s.

Rain showers move in Thursday evening

 

Low pressure spinning through west-central Illinois Thursday afternoon will continue to spread rain showers, some moderate to heavy at times, across northern Illinois and southern Wisconsin. Initially, the rain will be light and scattered but heavier pockets of rainfall will occur as the low moves closer to north-central Illinois tonight.

Some clearing taking place around the low has brought a few thunderstorms across central Illinois with a few funnel clouds being reported. That threat should remain south, closer tied to the low.

By Friday morning, the low will be weakening and drifting further north. Scattered rain showers will continue during that time, but by the afternoon skies will begin to dry out with some breaks in the cloud cover expected. Temperatures on Friday will warm into the upper 70s.

Rain chances stick around as we jump into fall

Rain Chances Continue:

Mother nature has been quite kind to us this week giving us rain chance after rain chance. So much so that our rainfall deficit for the month of September is now sitting under an inch. 

Fortunately, the "rain train" continues as a weak low, or something we call a Mesoscale Convective Vortex (M.C.V), lifts into the region from the south. 

With it will come an increase in moisture, resulting in the chance for a few isolated showers beginning after mid-day. Come Thursday evening/night, expect the coverage of this activity to increase slightly, passing through in a more scattered fashion. 

Heavier rain will be a possibility with any thunderstorm that develops, though severe weather thankfully will not be a concern.

 

Weekend System:

Rain chances simmer down a bit for Friday. However an isolated shower or thunderstorm cannot be ruled out at any point in the day. High temperatures because of the continued rain chances and expansive cloud cover will peak in the upper 70s. 

From there, our attention will then turn to a strengthening storm system over the Upper Great Plains. One that will bring a multi-day severe set up to those who live in the central plains and the Midwest. Rain chances for us don't spike until late Saturday night into Sunday. However, there is still a bit of time for forecast models to get a firmer grip on the finer details, such as timing and accumulations. High temperatures are expected to "fall" so to speak to a more fall-like feel, peaking in the low 70s Sunday through Wednesday!

Localized flooding for some Wednesday morning

 

Heavy rain producing thunderstorms returned for some late Tuesday night and Wednesday morning prompting a Flood Advisory to be issued for a portion of northern DeKalb County. The heaviest rain occurred over northern DeKalb County, southeast Boone County and Southwest McHenry County. Radar estimates of up to four inches of rain occurred in/around Genoa, IL. Slow moving and continuous thunderstorms occurred, producing extremely heavy rainfall through sunrise.

The rain has come to an end, but skies will remain mostly cloudy through the evening. Temperatures were able to warm into the upper 70s, to near 80 degrees Wednesday afternoon thanks to a little filtered sunshine. Temperatures Thursday and Friday will warm into the middle and upper 70s. Thunder chances return during the afternoon and evening Thursday, lasting into Friday.

Isolated rain early, same for Thursday

Rain Chance Early:

The Stateline saw quite a bit of rain Tuesday, especially during the morning hours. Overall, it was enough to push Rockford's daily total over .5". Rain chances extend into early Wednesday morning thanks to a warm front sliding through. 

While severe weather isn't a concern, expect the possibility for an isolated shower and storm into mid-morning. Once the warm front is positioned to our north, dry conditions settle in for the rest of the day. The combination of this afternoon's mixed sunshine and light southwest wind will help temperatures climb into the upper 70s for most, with a spot or two touching 80-degrees. Tonight remains dry. However, we do end up keeping a bit of cloud cover into Thursday morning. 

Isolated Chance Thursday:

Thursday will be very similar to Wednesday. Most of the day will feature mostly cloudy skies and dry conditions. However, a weak area of low-pressure, or something we call a Mesoscale Convective Vortex (M.C.V), with sling enough moisture northward for a few isolated afternoon showers. 

High temperatures because of Thursday's cloud cover will end up a few degrees cooler in the upper 70s. There won't be much of a chance for rain on Friday or Saturday as the strongest lift or forcing will be located to our west. But come Sunday, those chances will finally carry their way into the Stateline. Overall, the severe threat is low as there doesn't appear to be a lot of instability or atmospheric energy present. But something to definitely monitor!

Rainy start Tuesday morning

 

Skies will continue to clear Monday evening ahead of our next storm system that'll bring another round of rain early Tuesday morning. That system currently sits well to our west. For the remainder of Monday evening, skies will turn mostly clear as temperatures gradually drop back through the 70s this evening, into the 60s after sunset, and then into the 50s overnight. While our skies are clear now, cloud cover will increase overnight as both warmer air and moisture are pulled into the region.

The majority of Monday night will remain dry, but cloudy. Rain showers will move in after 4am Tuesday, lasting through late morning. There may be a rumble of thunder or two, but most can expect some heavier downpours through the morning commute. These will last through 9am before turning more scattered through Noon.

Temperatures will be a little cooler Tuesday afternoon with the cloudy and rainy start. Look for highs to warm into the upper 60s and low 70s. A break in the precipitation is expected Monday afternoon before another chance for a few showers and isolated thunderstorms return Tuesday evening. Some of this activity may carry over into Wednesday, with partly sunny skies expected Wednesday afternoon.

Rainfall totals will range between a quarter of an inch to half an inch, but heavier downpours could push those totals closer to an inch in some locations.  

Areas of fog likely Sunday night

 

Skies will continue to clear Sunday evening as low pressure pulls further away from the Stateline. Temperatures were able to warm into the upper 60s and low 70s following some breaks in the cloud cover during the afternoon, with locations southeast of Rockford remaining in the middle 60s.

Under mostly clear skies Sunday night temperatures will likely dip into the upper 40s. Winds will turn light as high pressure moves through Wisconsin, settling over the region. Clear skies, light winds, and moisture leftover from the rain Saturday night and Sunday will likely lead to areas of patchy, dense fog Monday morning. The fog will last until a little after sunrise, with visibility improving and skies turning partly cloudy during the afternoon. Highs on Monday will warm into the low 70s.

Be careful when you're out early Monday and remain aware of quickly changing visibility, especially in the rural and open areas. 

Rain returns Saturday morning and afternoon

 

Temperatures Thursday morning dipped into the 40s, low 40s for some, but were quick to warm into the low to mid 70s during the afternoon. This was all thanks to plenty of sunshine and dry air in place over the Great Lakes.

Air molecules in an air mass that is dry are able to move around more freely when warmed, causing temperatures to warm. This typically brings a big spread in temperatures the morning low to the afternoon high. This is what is known as the 'diurnal range' and is often why during the cooler months we tend to see a 30 (plus) degree temperature spread from low to high.

When an air mass has more moisture the air molecules are not able to move around as much, leaving a smaller spread between the low and high.

The dry air currently in place will play a role, initially, in our rain chances Saturday. A cold front stretching from the Upper Midwest into the Plains will slide closer to the Stateline Friday night. As it does, cloud cover will be the first to move in Friday evening. Skies are expected to remain dry Friday night, but a few light showers are possible Saturday morning.

A second cold front moving in Saturday afternoon will bring a slightly better chance for rain, and a few isolated thunderstorms, during the afternoon and evening. Severe weather is not expected at this time. 

Rainfall amounts will remain light and between a tenth of inch up to a quarter of an inch. Clouds will stick around Saturday night and into Sunday before clearing some Sunday afternoon.    

Sunshine returns Wednesday, Fog likely Wednesday night

 

Skies remained mostly cloudy through most of Wednesday morning following dense fog for some. Drier air moving in early afternoon allowed the cloud cover to break, bringing temperatures into the middle and upper 60s. As of 4pm, Rockford's current temperature was 70 degrees.

Skies will continue to clear with high pressure moving south through the evening. This will allow overnight lows to dip into the upper 40s once again. With clear skies and light winds areas of fog are likely to develop once again, becoming dense for some around sunrise Thursday morning. Be careful on the morning drive Thursday.

This type of fog is known as 'radiation fog' and develops as a result of a few things: light to calm winds, clear skies, and low-level moisture. Radiation fog is very common here in the Stateline, occurring often during the fall and winter months. As the air temperature cools during the evening and overnight it begins to stabilize. As the air temperature falls closer to the dew point temperature it reaches saturation, allowing fog to form. Fog develops first near the surface, thickening as the air cools, before extending upward through the night.

As the sun comes up the next morning temperatures warm, causing the fog to clear (most of the time). We'll see fog again Wednesday night, but a little more of a breeze and warming temperatures should limit fog development through the rest of the week.