Rainfall and flooding risk continues into Saturday morning

 Following a night of heavy rainfall where some portions of the state line experienced slow-moving thunderstorms that produced nearly 3" per hour rainfall rates, the flooding risk continues into the morning today. More showers and thunderstorms are expected to move in through the morning bringing more accumulating rainfall.

As of now, around 5:20 a.m. the state line is all clear of precipitation however just to our southwest near the Quad Cities, a new band of showers and thunderstorms has begun to creep its way north. More rainfall is expected throughout the morning, but how much and where this ends up is still in question.

The main corridor of heavier storms this morning looks to stay south of Highway 20 as most of the flood watches issued remain south of Rockford. A Flood Warning is in effect for eastern Ogle County this morning as well where areas within this warning have received over 3 inches of rain since last night!

Thunderstorms look likely to develop across the state line around 7-8 a.m. this morning with multiple "training" thunderstorms possible. This means they will form and line up right over the same area bringing heavy rainfall to similar locations. These thunderstorms look to stay mainly south of Rockford, but the entire state line should begin to clear by 12 p.m..

The flood watches this morning line up with not only the track of possible morning thunderstorms, but also the highest potential rainfall totals. Much of the state line looks to receive some precipitation, however more than others. Once again south of Highway 20 and even almost south of the I-88 corridor seem to be the areas with highest potential rainfall this morning and into the afternoon with totals up to 2 inches possible.

Because of the possibility of heavy rainfall, the Weather Prediction Center has issued a slight 2/4 risk for the possibility of excessive rainfall and possibly flooding due to last night's heavy rain and already saturated soil. If you see rising water or standing water on roadways, simply turn around instead of driving through it!


 
 

Scattered storms, heavy rain possible into Saturday

 A brief isolated shower East of downtown Rockford has been the majority of the rain activity so far today, but coverage has been increasing to the South and West as of 6:30PM. Scattered storms near and South of the Quad Cities will spread our direction through the evening.

On and off scattered storms will remain possible through the night and into early Saturday morning. The strongest storms may be capable of producing gusty winds and very heavy rainfall with rates up to 2" per hour. Any storms that train, or move across the same area repeatedly, will quickly develop a flash flooding threat.

In total, some spots in the Stateline could end up seeing between 0.5" to 1.5" of rainfall through the day Saturday. It will not be widespread for all, but narrow bands could end up seeing significant rainfall. Where those bands set up is still a bit uncertain, but those near and Southeast of Rockford have the best chance to see the heaviest rain.

A flood watch has been issued for parts of the Stateline through Saturday evening. The heaviest rain will be more hit-or-miss across the entire region, but flash flooding may be possible in areas that see such high rainfall rates. Be sure to heed any flash flood warnings that are issued!

Little relief from humidity following Thursday's cold front

High temperatures Thursday weren't quite as hot as they were Wednesday, but the humidity was just as high with dew point temperatures in the low to mid 70s. Unfortunately, those dew point temperatures won't fall much over the next few days as humidity is expected to remain high through early next week.

A cold front passing through the Midwest and western Great Lakes Thursday evening will continue to slip southeast through the night. As it does, a few scattered rain showers and isolated thunderstorms are possible. Patchy fog may also develop in areas where skies turn mostly clear.

Behind the front, however, dry air will be lacking leading to high humidity sticking around through most of the weekend and even into early next week. Dew point temperatures are likely to stay in the upper 60s and low 70s through the start of the weekend, rising into the mid-70s following a warm front Saturday and Sunday. This will help push the heat index back into the 90s Saturday, with the triple digit numbers returning Sunday and Monday.

The high moisture lingering through the weekend will also lead to a few more opportunities for showers and thunderstorms, especially with the close proximity of the faster winds within the jet stream and a frontal boundary meandering back and forth. It won't be until a pattern change late next week where we get some relief from the humidity.

In fact, the long-range outlooks for the beginning of August feature temperatures falling slightly below average over much of the Great Lakes and Northeast, with below average precipitation.  

Isolated thunderstorms remain possible into the weekend

 It was not nearly as hot and humid of a day as it was Wednesday, as the high in Rockford only reached the upper 80s. Most of the evening will remain dry but an isolated shower may be possible into the night with a chance for some patchy fog. Temperatures return to the low 70s with a little less humidity.

A few stronger storms may arrive early tomorrow morning as a weakening complex of storms slides in from the West. Best coverage of storm activity from this wave will be centered near and South of I-88. No severe weather is expected with this round, but heavy rain and gusty winds may be possible.

Friday afternoon looks to see storms only isolated in nature, but heavy rain and gusty winds will again be possible within the strongest storms. Coverage of these will gradually slide Southward into the late evening. Temperatures will again reach the mid-80s with similar humidity to Thursday for most.

Friday night into Saturday morning will be the next better chance for some scattered storms as a warm front begins to work through the area. Another round of storms from the West will track along this frontal boundary. Most of these storms will be East of us by the afternoon, leaving us only with a slim chance for an isolated shower or storm for most of the day.

The strongest of those storms Saturday morning may be able to produce a few isolated instances of gusty winds and small hail. There is a low-end Level 1/5 Marginal risk for severe weather across the Stateline for this threat.

Much of Saturday will remain dry after the morning storms, with high temperatures back into the mid-80s. Most of Sunday will remain dry as well, but we will see a bit more heat as temperatures return near 90°. Sunday and Monday will feature our next round of oppressive humidity, with heat index values near the triple digits.

Severe, heavy rain potential tags along with Thursday's heat

Last night was one of the more uncomfortable nights of the summer as temperatures only fell into the mid 70s. Dew points weren't too far off. In fact, values this morning are similar to values being observed across the state of Florida, mid 70s. Gross. 

 

 

Triple-digit heat indices are on the table once again for our Thursday. However, the potential for some relief is a little bit higher today as our next cold front slides in from the northwest. This could bring us two chances for storms, one late in the morning and one towards the evening drive. The evening bout would all depend on the cold front's timing.

 

 

If the cold front is slower and we do see development along the cold front closer to the Illinois-Wisconsin border, severe and excessive rainfall potential would be slightly higher. If the cold front is slightly faster than modeled and pushes through earlier, then the risk would be higher to our south and east. Right now, the Storm Prediction Center has the entire area under a level 1 of 5 for damaging winds.

At the same time, the Weather Prediction Center has us under a level 2 Slight Risk for excessive rainfall. With the amount of moisture in our atmosphere, thunderstorms would be able to produce rainfall rates at or above 1", making flash flooding a concern. Thunderstorm chances should wane into the night as the cold front pushes away and slides into the central portions of Illinois. This would leave us with a decent amount of cloud cover into Friday morning with overnight lows dropping into the low 70s. 

This active and warm weather pattern is set to carry on into the last weekend of July. Ridging to the south will keep temperatures above average, getting back to the 90° mark Sunday and Monday. Storm chances are best Saturday as a quick-moving low pressure system aims to track into Wisconsin. 

Similar to today, the Storm Prediction Center has the entire area under a level 1 Marginal Risk.

Humidity sticks around with scattered storms Thursday

 It felt closer to 100° than it did 90° through much of Wednesday afternoon, with a very hot and humid air mass centered overhead. Overnight, temperatures won't fall very far -- only back to the mid 70s for overnight lows. The heat advisory will be allowed to expire late this evening for Southern Wisconsin and Northeastern Illinois.

The warm start to the day tomorrow will kick off another hot and humid afternoon, with highs approaching 90° once again. This time around, scattered storms will be possible through the afternoon and evening. The storms may bring a little bit of relief from the heat and humidity as a cold front pushes through by late evening. But it may still feel near 100° with heat index factored in.

Storms will be mostly isolated in nature, with the first chances arriving toward daybreak and another chance by mid-day. These storms may produce some gusty winds and quick downpours, but should remain below severe limits.

Better coverage of storms will arrive Thursday afternoon into the evening, mainly after 2-3PM. These storms may produce a few instances of damaging wind gusts and some very heavy rainfall. Storms will gradually diminish in coverage into the late evening as the cold front pushes South. If storms get going earlier in the day, temperatures may not quite make it to 90°, especially for those North and West of Freeport.

For the low-end threat of a few gusty thunderstorms, the Storm Prediction Center has placed the Stateline under a Level 1/5 Marginal risk. The chances for large hail or a tornado is very low in this setup, so damaging winds will be the main concern.

Another threat with these storms will be heavy rainfall. With very abundant moisture aloft and a slow-moving cold front, storms may be able to produce rainfall rates above 1" per hour. If those storms track over the same area multiple times, flash flooding could be a concern. There is a slight risk for flash flooding criteria to be met across much of the Stateline Thursday.

Isolated thunderstorms may be possible again Friday and early Saturday with a bit of a cool-down. Highs will return to the mid-80s 

Triple-digit heat indices likely across northern Illinois Wednesday

A compact low pressure system, known as an M.C.V - mesoscale convective vortex - is swinging into southwest Wisconsin this morning. While most of the activity has remained to our northwest, we are seeing a few spotty showers and thunderstorms develop across northwest Illinois. Expect any chance for rain to come to a close before mid-morning. 

 

Our attention will then turn to today's heat. A Heat Advisory will be in place for all of northern Illinois and southern Wisconsin beginning at 10AM this morning. The portion that includes Winnebago, Boone, McHenry, Ogle, and Lee County will run until 10 PM. Stephenson, Carroll, Jo-Daviess, and Whiteside County will be under the advisory until 7PM. And finally, the portion that includes southern Wisconsin will run until 8PM.

High temperatures this afternoon will soar into the low 90s. That, combined with dew point temperatures in the mid to upper 70s (gross) will allow heat indices to climb above 100°, likely ending as high as 105°-108°. Heat safety, heat safety, heat safety! Make sure you are making that a priority this afternoon as well as passing the same safety to your loved ones, your pets, and to those who may not have a reliable source of air conditioning. 

Some relief arrives in the form of a cold front during the late stages of Thursday. This will bring afternoon highs down into the mid to upper 80s for Friday and for the start of the weekend. However, with the heat dome to our south expanding back into the central plains, we can expect highs to climb back into the low 90s for Sunday and Monday.