Dry Weather Continues, Rain Chances Return Overnight

Same Story, Different Day:

Weather-wise, this week has been rather enjoyable thanks to an area of high pressure locked over the Midwestern U.S. Each day has featured a good amount of sunshine, comfortable humidity, and highs in the lower 80s. While more of the same can be expected today, our dry stretch looks to come to an end overnight as a cold front inches closer. 

Patchy fog will once again be possible during the early stages of the morning. Otherwise, expect a few clouds to give way to a partly cloudy afternoon. The only difference between today and the past few days is the direction our wind is coming out of. With said high pressure system sliding to our east, winds this afternoon will be more out of the southwest. This wind change will bring temperatures up a degree or two while also bringing humidity levels up a smidge.

Rain Chances Return:

Fortunately, there's nothing to be concerned about during the drive home this evening as skies remain partly cloudy into tonight. It's towards the midnight hour we see a few more clouds slide in, with rain chances not too far behind. 

Forecast models suggests that a round of scattered showers and thunderstorms may slide into our area during the predawn hours Thursday. At this point in time, the potential for severe weather appear is very low, though a few downpours wouldn’t be out of the question.

The cold front itself doesn't look to enter the region until the late afternoon/early evening time frame. With it does come another opportunity for a few showers and thunderstorms. Similar to the first round, severe potential is low. 

In fact, the Storm Prediction Center placed the entire Stateline under the general or non-severe thunderstorm risk, with areas to our northwest being placed under a Marginal Risk (level 1 of 5). We'll see if they push that eastward in the updates that follow. Otherwise, rain chances look to come to an end Thursday night into early Friday, with dry conditions sticking around for the work week. Temperatures look to fall following Thursday's frontal passage, with most spots peaking in the upper 70s Friday afternoon. Southwest winds quickly take over Saturday and Sunday, bringing temperatures back into the low to mid 80s.

Rain chances return Wednesday night/Thursday

 

Over 7 inches of rain has fallen so far during the month of August , putting us at a 4 inch surplus; quite the difference from just a few months ago. The most recent deluge came down just last weekend where several inches of rain occurred over potions of northwest Illinois.

The last several days have been dry, and that trend is one that'll continue into Wednesday. But our dry stretch will be coming to an end late Wednesday night and Thursday as a cold front moves in from the west and northwest. High pressure leading up the arrival of the cold front means there won't be a significant amount of moisture in the atmosphere but showers, and even a few thunderstorms, are expected to move in from west to east Wednesday night, lasting through at least Thursday morning.

The cold front will pass Thursday afternoon with another area of high pressure quickly settling in behind. This will help turn our skies dry and partly cloudy through Saturday, although an isolated shower/storm can't be ruled out Saturday afternoon. 

Rainfall totals Wednesday night and Thursday won't be as high as our last rain events, but a few locations could receive between a quarter of an inch to half an inch. Those amounts look to fall in eastern Iowa and northwest Illinois. You'll also notice the humidity going up Thursday ahead of the front as dew point temperatures are expected to climb into the mid and upper 60s. They should drop right back down Friday, before rising once again into the weekend.  

More of the Same, Pattern Change Arrives This Weekend

Rainfall Comparison: 

As we discussed yesterday, Rockford has seen quite a bit of rainfall during the month of August. So much so that our monthly total of 7.36" sits in the top 5 for wettest Augusts on record. But that's since the beginning of the month. 

The Dallas/Fort Worth area on the other hand observed that and much more in just a 24-hour time period thanks to a slow-moving frontal boundary. In fact, the airports total of 9.19" now ranks as the second highest 24-hour precipitation event since September 4-5th, 1932, when 9.57" of rain fell during that 24 hour period. This of course not only led to significant flooding across the Dallas metro area, but also in other cities and towns throughout northern/northeastern Texas. 

More of the Same:

Locally, high pressure remains in control. Meaning, you can take the weather we had yesterday and insert it into today's forecast. If you plan to travel during the morning commute, be on the lookout for patchy fog. Some good news, the low-levels of our atmosphere doesn't have as much moisture present as it did during the early stage of Monday. 

So, the fog this morning shouldn't be as dense and as widespread. Once the fog lets up, this morning's sun-filled sky is expected to give way to a few fair-weather cumulus clouds by this afternoon. With a light northwest wind in place for much of the day, temperatures and humidity remain comfortable. Both however do creep up a bit for Wednesday as winds will be more out of the south.

Late-Week Pattern Change:

Guidance does then show a weak cold front sliding in from the north and west Wednesday night into the early stages of Thursday. Ahead of it does look to be the potential for a few showers and isolated thunderstorms. Thankfully, the severe threat looks very low at this point in time. Highs look to drop a smidge before climbing over the weekend.

Along with the climb in temperatures does come a surge of moisture, especially once winds change to the southwest following Sunday's warm front. This will once again bring the potential for a round of scattered showers and thunderstorms, one that looks to last into early next week. Similar to Thursday's chances, the severe threat is low. 

But we'll have to see how forecast models trend with this weekend's forecast as we're still a couple of day out. But it will definitely be something to keep an eye on if you have any late-summer plans this weekend. Temperature-wise, it does look like Sunday will have the best potential of approaching the 90-degree mark. This heat may carry on into Monday. However, models this morning we're still unsure of the timing of the cold front.

Extreme drought can worsen flash flooding during heavy rain

 

Heavy rainfall during drought conditions may not always be a good thing and can actually cause flash flooding to become worse when it occurs. Dallas, Texas went from exceptionally dry (drought) conditions, to the second wettest August on record in a matter of hours as heavy rain fell across central and east Texas late Sunday night and Monday morning. Heavy rain continues to fall south of the Dallas/Ft. Worth area Monday evening, but flooding concerns continue with Flood Watches through Monday evening across Texas, but lasting through Tuesday evening in Louisiana.

Numerous rainfall records were broken in the DFW as the 9.19 inches of rain they received was the second highest 24 hour precipitation event since September 4-5th, 1932, when 9.57 inches of rain fell during that 24 hour period. Significant flooding has taken place not only across the Dallas area, but also in other cities and towns throughout Texas. Heavy rainfall is expected to continue Monday night into Tuesday.

It comes as no surprise that many across the Plains and out West have been baking in the heat as temperatures over the summer months have soared well over 100 degrees, multiple times. The extreme heat and lack of rainfall has only made the drought conditions worse west of the Mississippi River. Nearly the entire state of Texas has been either in the 'extreme' drought or 'exceptional' drought condition category for quite some time. And while the rain they received the last 24 hours will help some, the drought likely made the flash flooding worse in some locations.

Soil that is dry, hard and cracked acts just like a hard surface. So as heavy rain quickly falls on that hard surface, the rain drops tend to 'bounce' off the soil, rather than soaking in. This in turn causes more runoff which only adds to the flooding risk. Areas that are experiencing drought conditions benefit more from a prolonged, soaking rain - one that occurs for a couple of days at a slower and steady pace. While the soil may still be dry, hard and cracked the slow and steady nature of the rain allows the soil to soak in the rain more efficiently. While there may still be some issues with flooding, it typically isn't as extreme or devastating as when it occurs during a heavy rain event.

Foggy Mornings Ahead, Dry Thanks to High Pressure

Very Wet August:

The Stateline has seen an excessive amount of rainfall since the month of August began. As of this morning, the month to date rainfall total sits at 7.36", which is now ranked 3rd for wettest Augusts on record for the Rockford Airport. 

Thankfully, the faucet turns off for the early portions of the week as high pressure takes control of our atmosphere. But each day does look to start off with a round of patchy dense fog. 

Foggy Morning:

When the low-level moisture left behind by this weekend's rainfall combines with clear skies and light/calm surface winds, this creates a conducive environment for fog to develop. 

While the nature of this morning's fog doesn't look to become widespread, a few of our local airports are registering visibility at or below 1 mile. To be safe, give yourself a little extra time this morning for travel. Also, it's important to remember to use your low beams headlights as well as to leave plenty of distance between you and the cars in front of you to account for any sudden stops or changes. 

Dry Start to the Week:

Once the fog lets up, a sun-filled morning sky will give way to a few fair-weather cumulus clouds by the afternoon. In a similar fashion to Sunday, highs will peak right around average.  

More of the same can be expected for Tuesday and Wednesday as skies remain partly cloudy, with high temperatures peaking in the lower 80s. The only rain chance we're keeping an eye on is Thursday into early Friday where a few showers will be possible. Otherwise, it will be the rise in temperatures that we see for the upcoming weekend that will take over the weather headlines. With warmer flow setting up, highs climb into the low to mid 80s for Saturday, with upper 80s expected for Sunday.

Fog impacts on driving

 

The fog early Sunday morning was quite dense in a few locations, prompting the National Weather Service to issue a Dense Fog Advisory for some across northern Illinois and southern Wisconsin. Most of the time the fog is quick to burn off following the sunrise and atmosphere beginning to mix a little more, but there are other times where the fog can last through much of the day. That was not the case, however, Sunday morning. The fog was quick to burn off leaving skies partly cloudy for much of Sunday afternoon.

Visibility can be severely impacted when the fog is dense, dropping down to only a few hundred feet if thick enough. This type of dense fog is extremely dangerous and can result in major accidents on the roads.

When driving in dense fog, you often have very little time to react to other vehicles or objects that may also be on the road and hard to see. For example, when driving at highway speeds of 60 mph your reaction time will be significantly reduced once that object becomes visible - depending on how dense the fog is.

When traveling at 60 mph, visibility of only 100ft gives you a reaction time of just 1.1 seconds. Visibility at 100 yards at 60 mph gives a reaction time of only 3.4 seconds. And visibility at a quarter of a mile (which can occur often here in the Stateline) your reaction time is only 15 seconds. When we drive, we use our surroundings to help us gauge how fast we are going (along with our speedometer). Our speed can sometimes actually increase in foggy conditions because we lose sight of the objects around us. That's why it is so important to make sure driving has your full attention - not distracted by the radio, phone, etc - and you are slowing down when it's foggy outside. Use your low beams, not your high beams, and remain aware and alert of what is around you. Make sure to leave plenty of distance between you and the car in front of you to account for any sudden stops or changes. To make sure you are following the proper lane, use your eyes to follow the lines on the road. The next couple of nights could be foggy ones, with locally dense fog possible for some. 

Heavy Rain a Big Possibility This Weekend, Low Severe Threat

Friday's Forecast:

A few isolated showers and thunderstorms will be possible in portions of far northwest Illinois through sunrise. Partly cloudy skies are to follow, with high peaking in the mid to upper 80s. 

It's during this "dry time" where the atmosphere will recharge, allowing a secondary round of showers and thunderstorms to develop to our west, shifting eastward as time progresses. With a lot more moisture to work with, this round will bring the potential for heavier downpours. This round looks to come to an end by Saturday morning, but additional development will occur as both the surface and upper level low approach the region.

Weekend Chances:

Forecast models then spirals the surface low into the northern half of Illinois during the latter half of the day Saturday. With it comes the likelihood for showers and a few isolated thunderstorms, some of which could be strong to severe. 

Earlier this morning, the Storm Prediction Center placed a majority of the Stateline under a Marginal Risk (level 1 of 5) for severe weather. Any storm that does show severe characteristics will be able to produce damaging straight-line winds and small-sized hail. With the extra "spin" from the surface low pushing on through, I wouldn't be surprised if any of the stronger showers or thunderstorms do showcase a funnel or two. With that being said, the tornado threat is very low.

Rain chances from there look to carry on into the early portions of Sunday. However, as the surface low exits the western Great Lakes, so will our opportunity for showers and thunderstorms. 

Expect conditions to turn a bit more quiet for the late-day hours Sunday with temperatures peaking in the upper 70s. Unlike the last time we were forecasting a multi-day rain event, flooding should not be a concern this time around. High pressure then takes hold of our atmosphere for the beginning of next week, allowing a good amount of sunshine to return. High temperatures do climb a few degrees, peaking in the low 80s into Wednesday.