June 2011 Archives

Thanks to Susan Carr of Winfield, IL for sharing this beautiful Alaskan shot from her niece, Tristan Wagner of Fairbanks, Alaska.

The National Weather Service has issued a Heat Advisory for northern Illinois, southern Wisconsin and Lake County, Indiana for Friday afternoon and evening. Hot humid air will flow into this area with temperatures peaking Friday afternoon in the upper 90s - close to 100 degrees - and heat indexes in the 105 to 110-degree range.

Today low pressure is centered over North Dakota with a cold front to the southwest and a warm from southeast through central Iowa. Heat and humidity is currently concentrated in the plains to our west. Readings this afternoon will be in the 90s to the lower 100s from Texas north to Minnesota. Southerly winds are pumping humid air into the plains with a tongue of 70 to 75-degree dew point air from eastern Texas and western Louisiana north through eastern Oklahoma and western Arkansas, eastern Kansas and western Missouri, eastern Nebraska and western Iowa and eastern North and South Dakota and western Minnesota.

This weather will be moving east with the warm front passing through the Chicago area later tonight and early Friday. Scattered thunderstorms could occur along and ahead of the warm front over Wisconsin and Michigan into northern Indiana - possibly clipping the northeast corner of Illinois including the Chicago area late tonight and early Friday.

This afternoon, under mostly sunny skies, temperatures should warm well into the upper 80s - approaching the 90-degree mark in a few locations. Overnight southwest winds behind the warm front will push the warmer, higher dew point air across Illinois into the Chicago area -  temperatures will probably stay in the lower to middle 70s, setting the stage for tomorrow's near 100-degree heat and associated dangerous heat indexes approaching 110 degrees.

 Individuals should be making plans to stay out of the sun and in shaded or air conditioned areas Friday afternoon and night.The warm air will still be in the area Friday night, so there will be no relief from the heat and humidity until the heat-busting cold front moves across northeast Illinois Saturday. Thus the near 100-degree day Friday will be sandwiched between two very humid nights with temperatures in the 70s.

10 states, including Illinois, have some type of heat advisory in effect today as a dome of scorching heat stretches from the plains northward through the Great Lakes.  Tomorrow will probably be the hottest day of the year hear so far, eclipsing the 96 degree high back on June 7th.   If we climb past 96, it will the be hottest day in 5 years.  The heat index tomorrow will be somewhere between 100 and 105.  It is possible a few spots could hit 100.  Last time that happened was back on July 24th, 2005 when the mercury climbed to 102.

Speaking of hot...

Worldwide, 2010 was one of the two warmest years since official record-keeping began in the late 19th century.  That is according to a new report released from NOAA.  The 2010 State of the Climate Report has many interesting findings.   Here are some of the highlights:

• The Arctic is warming about twice the rate of the lower latitudes
• Their is some evidence the water cycle is becoming more vigorous.  Where there was higher evaporation the oceans were saltier than average and where there was more precipitation, they were fresher.
• The concentrations of major greenhouse gasses are on the rise. Carbon dioxide increased by 2.60 ppm. That is more than the average annual increase seen during the last 30 years.

368 scientists from 45 countries took part in the peer-reviewed report.  Both El Nino and the Arctic Oscillation were cited as playing a key role in 2010's weather and climate.

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The center of low pressure that dominated our weather the past few days has moved northeast of Lake Superior into the southeastern portion of Canada's Ontario province, and its associated cold front that swept through Chicago late Monday afternoon is now approaching Pennsylvania. High pressure centered over eastern Nebraska will be moving through Iowa today and northwest winds on the front edge of that high pressure are flowing over southeast Wisconsin, northeast Illinois and northwestern Indiana.

Skies over the Chicago area will be sunny today. Northwest winds 10-20 mph will slowly diminish later this afternoon and evening as the high pressure center approaches from the west. Temperatures should rise to near normal levels this afternoon, reaching the upper 70's and pushing into the lower 80's in many locations. The normal high for this date is 82 degrees.

Clear skies will prevail tonight as the center of high pressure slowly moves over northern Illinois. Tomorrow's weather will be similar to today, only winds will become more east to southeasterly as the center of high pressure edges east of the area. A Lake breeze will probably develop Wednesday afternoon, so that there will be about a 10 degree temperature range from the lower 70's at the Illinois Lake Michigan shoreline to the lower 80's well inland both to the west and south.

There have been 55 reports of tornadoes, 247 reports of hail greater than 1 inch in diameter and 474 reports of wind damage so far this year in Illinois.  Illinois State Climatologist Jim Angel has the details. 

It has been an active year here for severe weather and even more active in the south and southeast with historic tornado outbreaks.   This has kept the folks at the National Weather Center very busy.   I had a chance to tour their facility in Norman, Oklahoma recently as part of a weather conference held nearby in Oklahoma City.

The modern facility right in the heart of tornado alley houses the Storm Prediction Center, the National Severe Storms Laboratory, University of Oklahoma's School of Meteorology and the local National Weather Service office that serves most of Oklahoma and northern portions of Texas.   The goal is to break down barriers between commercial interests, academia and the government and form a partnership to help understand and better predict our weather.

If you are ever in Norman, Oklahoma, drop in for a visit.  It is a weather geek's dream.  Check out the "Flying Cow Cafe" and see Dorothy, the weather probe featured in the film Twister.

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What was considered to be a rather weak high pressure system was expected to move through the Midwest Saturday into the eastern Great Lakes last night allowing cloudiness from a developing central plains low pressure system to overspread this area today. Instead the high centered over Lower Michigan this morning, and cool dry southeasterly flow on the near back side of the high persists over the Chicago metro area.

Sunny skies will probably hold over southeastern Wisconsin, northeast Illinois and northwest Indiana today, with the high pressure center slowly drifting east. Temperatures will likely warm into the lower 80's this afternoon in most inland areas, holding in the lower to middle 70's right along the Lake Michigan shoreline.  Areas to the far south and southwest might even reach the middle 80's.

High and mid-level cloudiness should overspread the area from the west tonight as the low pressure system approaches. Showers and thunderstorms could begin as early as late tonight, but indications are the most intense portion of the storm system will hit late morning and early afternoon Monday. The National Storm Prediction Center has all of Illinois and Indiana as well as portions of southern Wisconsin and lower Michigan in the slight risk of severe storms category for tomorrow.

A band of showers from the northwest corner to the southeast corner of Illinois was tracking east late this afternoon. The showers were light and beginning to move into drier air resting over northeast Illinois. Sprinkles or brief light showers are expected as the band passes over the Chicago metro area this evening. The back edge of the rain should be east of the city, out over the southern tip of Lake Michigan well before midnight.

The severe thunderstorm watch for the southern third of Illinois has been cancelled as those storms have weakened and for the most part moved into southern Indiana.

Low pressure continues to strengthen over the Oklahoma Panhandle with a warm front extending east out of the low through central Missouri into southern Illinois. Along and north of the warm front a band of strong thunderstorms has developed and moved east out of Missouri into southern and central Illinois and southwestern Indiana. The National Storm Prediction Center has issued a severe thunderstorm watch covering the southern third of Illiinois and southeastern Missouri until 8PM CDT this evening..

As the stronger storms pass well to the south, the southern flank of northern Illinois and northwest Indiana could get grazed by showers and even a few thunderstorms late this afternoon and tonight. Showers/thunderstorms will probably stay south of the immediate Chicago area.

High cirrus clouds associated with the storms to the south and west have spread over the Chicago area. An east to southeast lake breeze has enhanced the slowly establishing southeast winds north of the warm front. As a result, temperatures have leveled off in the mid to upper 70s and will probably lose a few degrees the reminder of the afternoon along and close to the Illinois Lake Michigan shoreline.

An ever-so-slowly-thinning deck of stratocumulus clouds will hover over southeast Wisconsin, northeast Illinois and northwest Indiana this afternoon. The low pressure center that has dominated Chicago area weather for the past few days is finally receding northeast of Lake Huron into the southeastern portion of Canada's Ontario province. As the low pulls away, the cloud cover will slowly recede with it. There will be increasing periods of sunlight shining through breaks in the overcast later this afternoon with skies gradually clearing tonight as a weak high pressure air mass passes over the Midwest and western Great Lakes.

Temperatures this afternoon should warm into the lower 70s as west to northwest winds diminish with the approach of the center of high pressure. Temperatures will fall through the 60s this evening into the mid to upper 50s after midnight tonight.

Saturday the center of high pressure will move east, and south to southeasterly winds will pick up on the backside of the high. Mostly sunny skies combined with the southerly winds should allow readings to approach 80 degrees over much of the area Saturday afternoon. Temperatures may be dampened a bit - holding in the lower 70s - right along the Illinois Lake Michigan shoreline.

Low pressure centered over northern Lake Michigan and moving very slowly northeast, dominates most of the Midwest and Great Lakes weather today. An extensive stratocumulus cloud deck covers Minnesota, Wisconsin, Iowa, and Upper and Lower Michigan as well as most of Missouri, Illinois, Indiana and Ohio. Periodic and very widely scattered light showers are triggered by minor upper air disturbances pinwheeling around the counterclockwise-rotating low.

Over Chicago and northeast Illinois as well as southeast Wisconsin and northwest Indiana mostly cloudy skies interspersed with occasional peeks of sun and a few very widely scattered brief light showers will prevail today. Chicago will experience west winds gusting as high as 25 to 30 mph flowing around the southern perimeter of the low pressure system. Temperatures will probably level off in the lower 70s, then fall through the 60s later this evening, dropping off into the upper 50s well after midnight tonight.

by Mike Hamernik

National Weather Sevice meteorologists from Romeoville will be conducting storm surveys in DuPage, Cook and Lake Counties today.  Straight-line winds are believed to be the root cause of most, if not all of the damage that occurred Monday evening. 

There are five general types of straight line winds.  Downburst, microburst, gust front, bow echo and derecho.  Of those five, downburst and gust front winds were depicted on radar between 8PM and 9PM over the west and northwest suburbs of Chicago.

There remains the possibility these winds spun up a brief gustnado. A gustando is not considered a tornado, and develops in a much different way than the classic supercell tornado. 

RIGHT: Photo of a microburst (not a tornado) over Oklahoma.  

Winds are gusting out of the south to southwest this morning, and by 9AM temperatures were in the lower 70s. However dewpoints were some 10 degrees lower than yesterday - running in the lower 60s giving a fresher "feel".

Low pressure centered over southeastern Minnesota will slowly move east into western Wisconsin today. This morning the system cold front bows out ahead of the low through Wisconsin and eastern Illinois back into Arkansas. Clouds and showers associated with the low center extend over all of Iowa and Minnesota and a good portion of western sections of Wisconsin and Illinois.

As the low center and cold front move east, this cloud cover will spread over northeast Illinois and winds will be gusting more and more out of the southwest and eventually the west. Widely scattered showers will occur in this unstable air, especially this afternoon and evening. Temperatures will probably level off in the middle, possibly upper 70s - then slowly fall later this afternoon.

Dew point temperatures today are expected to soar into the low to mid 70s, reaching their highest levels of 2011 to date.  The high humidity will result in a bad hair day for many of us, as well as provide fuel for thunderstorms that should hold off until this afternoon. 

The heat index, or "feels like" temperature, may reach the mid to upper 90s for several hours this afternoon. 

BELOW:  Current dew point temperatures: 70 degrees = humid    75 degrees = oppressively humid

Low pressure is centered over south-central Nebraska this evening. The associated warm front extends along and south of Interstate-80 through Iowa and Illinois into Indiana. A cold front extends to the south out of the low center into the Texas Panhandle. Overnight the center of low pressure should move into eastern Nebraska with the warm front swinging north through the Chicago metro area. Scattered showers and a few thunderstorms may develop over northeast Illinois in the vicinity of the warm front.

Tonight winds are expected to slowly shift from the southeast to the south, pulling more humid 70-degree dew points into northern Illinois. Tomorrow looks to be very warm and humid with high temperatures possibly pushing into the lower 90s. The cold front will trigger storms over Iowa as it moves east Tuesday, crossing the Mississippi River later in the day. With the warm humid air mass in place and a cold front approaching from the west, severe thunderstorms are likely to develop in western Illinois moving into the Chicago area Tuesday evening or overnight.

A second surge of showers and a few thunderstorms will spread east across northeast Illinois into northwest Indiana late this morning into the early afternoon. The associated weather this time around is not expected to approach the intensity of the band of strong storms that passed through central and southern portions of the Chicago metro area earlier this morning.

A warm front extends east out of developing low pressure in northern Kansas through northern Missouri across the Chicago area into southern Lower Michigan. As the low pressure center moves into eastern Nebraska, the warm front is expected to hover over northeast Illinois the next 24 hours keeping the Chicago area in an area of periodic shower and thunderstorm activity. There is plenty of moisture available aloft, so heavy downpours could accompany some of the stronger storms.

 Late this afternoon toward evening, triggered by an upper air impulse originating in the central plains, another band of strong, potentially severe thunderstorms could move east out of northwest Illinois into the Chicago area.

Clusters of slow moving thunderstorms have delivered too much rain to parts of the Midwest. 

6.20"  New Berlin, IL

5.50"  Olney, IL

5.30"  La Crosse, WI

5.24"  Effingham, IL

4.89"  Onalaska, WI

4.74"  Eau Claire, WI

4.30"  La Crescent, MN

2.48"  Indianapolis, IN

0.51"  South Bend, IN

0.00"  Chicago- O'Hare

BELOW: Rainfall estimate from doppler radar shows Chicago has been surrounded by rain over the last 24 hours. 

Through 7AM Sunday, nary a drop of rain has fallen this weekend in Chicago.  Location and luck has a lot to do with the fact we have stayed dry, while some communities in the Midwest are begging for the rain to stop.   

Up to 8 inches of rain has fallen since Friday night west of Springfield, Illinois, where Interstate 72 was forced to close for much of the day yesterday due to high water. North and west of Chicago, over four inches of rain fell Saturday night in La Crosse and Eau Claire, Wisconsin.   Mudslides occurred along Interstate 94 near Eau Claire where most of the 4 inches of rain fell in under 2 hours.    

Eventually the showers and storms will catch up with us as the weather pattern across the region remains rather unsettled.  Although most of the day will be dry, thunderstorm chances will be on the increase, peaking during the late afternoon and evening hours. 

 BELOW:  Current radar

Dear Tom,
I was recently in Texas and the TV weather people kept referring to the dryline. What is it?
--Alan Ceschin

Dear Alan,
The dryline is a low-level boundary or transition zone separating moist air from dry air. It occurs worldwide, and in the United States a prominent one is found over the southwestern Plains marking the boundary between moist air with dew points in the 60s and 70s from the Gulf of Mexico and dry continental air with dew points in the teens and 20s arriving from the southwestern deserts. Because dry air is denser than moist air, a dryline acts like a cold front, lifting the moist Gulf air and initiating thunderstorm activity that can become severe. Typically the southern Plains dryline advances east during the day and retreats to the west at night. Knowing its location helps forecasters determine where thunderstorms will develop.

Much of central and southern Illinois was soaked overnight with up to 6 inches of rain.  Widespread flooding is being reported in and around Springfield and Effingham Illinois.  Interstate 72 west of Springfield had to be completely shut down this morning due to flooding.

Here in northern Illinois, we made it through the night rain-free, and it appears most of the daylight hours today will be dry, with just a slight chance of a shower or thunderstorm.  Our weather situation changes tonight as low pressure over Kansas drifts east into Iowa increasing thunderstorm chances substantially.

Here are a few rainfall tallies from southern and central Illinois:

6.20"  New Berlin 

4.90"  Loami

4.25   Jacksonville

by Mike Hamernik http://twitter.com/#!/MikeHamernik

A small and weak tornado briefly touched down Wednesday evening 18 miles south of downtown Chicago in South Holland, Illinois.  The tornado lasted only two minutes, traveling under a mile after making first contact with the ground near the Bishop Ford Freeway.

Roof and shingle damage was reported, but there were no injuries.  The tornado was rated EF0 with winds of 65mph to 85mph. 

EF0 tornadoes rarely result in injuries or fatalities.  Of the 916 tornado deaths reported since 2005, only one fatality has been attributed to an EF0 tornado. 

Fortunately, atmospheric conditions across northern Illinois on Wednesday were not conducive for strong or long track tornadoes. 

The National Weather Service has posted a complete damage report on their website.

BELOW: Path of Wednesday evenings tornado in red  (courtesy NWS Romeoville)

The FDA issued new rules this week for sunscreen labeling.  For the first time, sunscreen labels will be able to carry the claim that they can prevent the early aging of skin and protect against skin cancer.  The new rules are meant to reduce confusion for consumers.

Here is a summary of the new guidelines from an article in The Los Angeles Times:

Under the new guidelines, sunscreens may be labeled "broad spectrum" if they block UVB radiation and a percentage of UVA radiation. UVB is the major cause of sunburn, while both UVA and UVB cause early skin aging and skin cancer.

Products that are broad spectrum and have a sun protection factor of 15 or higher may be labeled to say that they reduce the risk of skin cancer and premature skin aging. Conversely, those that are not broad spectrum or that have an SPF lower than 15 will be required to carry a warning that they have not been shown to reduce such risks.

Sunscreens will no longer be able to claim to have a specific SPF above 50: The highest category now will be 50+.

Products will no longer be allowed to be labeled as sun blocks because there is no evidence that they block all the radiation in sunlight. Products also may no longer be labeled "waterproof" or "sweat proof." Instead, they can only be called "water resistant," and labels must state clearly how long such protection lasts -- either 40 minutes or 80 minutes.

The summer of 2012 is the first time we will see the labels that meet the new requirements.

So sunscreen is in the news today and the sun itself is making news. Scientists say there is evidence that the sun could enter a prolonged period of relatively quiet sunspot activity.  It could even be similar to the "Maunder Minimum".  That occurred over a 70-year span between 1645 and 1715.  That minimum solar activity period happened at the same time Europe and other parts of the world saw unusually cool weather, a period known as "The Little Ice Age".  Sunscreen activity is expected to peak in its current cycle sometime in 2013.

  Wildfires continue to burn in the southwest as the widespread drought deepens.  Large portions of many states are experiencing drought.   The U.S. Drought Monitor keeps tabs on drought conditions. Parts of several states are experiencing "extreme" and/or "exceptional" drought conditions.

Here is a list of states affected by drought and the percentage of those states currently enduring drought conditions:

Arizona 56%

Oklahoma 59%

New Mexico 94%

Texas 97%

Louisiana 100%

Some are blaming the recent strong La Nina for the dry conditions south and the relatively wet spring conditions north.  La Nina is a period of colder-than-average sea surface temperatures in the eastern equatorial Pacific Ocean. The good news is the La Nina is officially over. Sea surface temperature's in the Pacifica Ocean should remain near normal through the rest of summer.

It is feast or famine when it comes to precipitation.

Much of the Sierra Nevada mountain range, the Cascades and the northern Rockies, remain buried under a thick layer of snow.   The snowpack is helping to fill reservoirs and replenish fresh water that supplies much of the region.   If this summer starts off to warm though, the piles of snow could turn into floodwaters.  This is fifth-thickest spring snowpack in the Sierra they have seen in 60 years. 

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A steady northeast wind off the still chilly waters of Lake Michigan (shoreline water temp 57 degrees) will lead to a cool and crisp day along the lakefront and at the beaches.   Highs well inland (Geneva, Naperville) will reach 70 degrees while readings along the lake will be stuck in the 50's.    

BELOW: Current temperatures.  Updated every 20 minutes. 

Leftover moisture from a departing storm system will linger over the Chicago area today in the form of clouds and fog.   Occasional drizzle and mist is expected, especially in suburbs and neighborhoods lining the shores of Lake Michigan. 

Isolated heavier showers that popped up early this morning will move east of Chicago by this afternoon, but damp conditions will persist until this evening. 

BELOW: The view from our WeatherBug camera located at North Avenue and Lake Shore Drive at 7AM.  A misty dense fog is blanketing much of the lakefront as well as many northern suburbs

Early this morning a band of showers and thunderstorms broke out north of a west-east oriented warm front that extended from low pressure over the Texas Panhandle through Oklahoma - central Missouri - and the central portions of Illinois, Indiana and Ohio. This band of precipitation should slowly weaken as it passes east of Chicago out over southern Lake Michigan later this morning. Brief heavy downpours will occur in some locations.

A lull in shower activity should occur later this morning and the sun could break out for a while. Then as heating picks up and the warm front begins to move north, another round of showers and thunderstorms will probably brak out over northern and central portions of Illinois and Indiana later this afternoon and evening. With the support of an upper air impulse riding over the northern plains into the Midwest, strong - possibly severe storms could erupt later this afternoon over the Chicago area. The National Storm Prediction center has outlooked a good portion of the area on either side of the warm front for a slight chance of severe storms today and tonight - all the way from Oklahoma through Missouri, most of Illinois, Indiana and Ohio and a portion of southern Lower Michigan.

Cooler air came crashing in on strong northeast winds yesterday after one of the earliest and hottest heat waves at Midway Airport in 78 years.   The warmest temperatures we see in the next seven days are highs near 80 degrees by the middle of next week. 

The 90s might be gone for now but it is only a matter of time before we experience them again.   When heat waves develop in the not too distant future, they may be worse than ever.  A recent study from Stanford University suggests the United States is "likely to undergo extreme summer temperature shifts within 60 years."

The study's lead author says, "large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years."

Heat waves on steroids is how Capital Weather Gang's Jason Samenow puts it.   His recent blog explores NCAR's study of how a relatively small shift in the average global temperature will result in "a large change in extremes".

NCAR's research shows that there are nearly twice as many daily high temperature records being set compared to daily record low temperatures today.   In the 1950s the ratio of high temperature records compared to low temperature records was about even.

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by Mike Hamernik http://twitter.com/#!/MikeHamernik

Below is a visual depiction of Chicago area rainfall estimates from doppler radar.  Hardest hit were the west, southwest and south suburbs while northern Cook County experienced the least rainfall.

Blue=  Less than 1"     Yellow = 3.00"     Light Orange = 3.50 to 4.00"    

Dark Orange = 4.00" to 5.00"   

by Mike Hamernik http://twitter.com/#!/MikeHamernik

Heavy rains have flooded many roads throughout northern Illinois and northern Indiana.  Hardest hit have been Chicago's southwest suburbs.  Here are some of the more impressive totals.

5.29"  Romeoville

5.01"  Plainflield

4.91"  Joliet

4.35"  Lemont

4.35"  Hinsdale

4.05"  Oswego

4.01"  Joliet

3.97"  Flossmoor

3.80"  Aurora

3.76"  Homer Glen

3.70 " Crete

3.23"  Chicago- Midway

2.95"  Crown Point

2.60"  Lakes of the Four Seasons

Not everyone experienced the excessive precipitation. Rainfall totals over many north and northwest suburbs were only around one inch. 

1.12"  Gurnee

1.10"  Chicago-O'Hare

1.02"  Elgin

0.83"  Woodstock

0.49"  Evanston

The National Weather Service has extended the Flash Flood Warning for much of the Chicago area until 5:30PM. 

The rain has ended for now, but the effects continue.  Many roads in Chicago's southwest suburbs remain flooded.  Some are closed including Illinois Street and New Avenue in Lemont

Rapid rises are still occurring on many creeks and streams. 

Use extreme caution navigating roads that are covered in water.  Don't attempt drive through flooded dips or low water crossings, and never try to cross a flowing stream. 

BELOW:  Counties in Illinois and Indiana shaded in orange are included in the new Flash Flood Warning that runs until 5:30PM. 

A disturbance along a quasi-stationary frontal boundary oriented east-west south of Chicago between theInterstate-88 and Interstate-80 corridors triggered a "training" or repeated passing of thunderstorms over the same area this morning. The disturbance weakened somewhat as it since moved east into northern Indiana. Rainfall totals of 3 to 4 inches were recorded resulting in widespread flooding of streets, roads and highways, even a portion of Interstate-55 near Route 83.

While the frontal boundary could drift south, it will still lie in close proximity to the same area, and thunderstorms could easily redevelop aided by afternoon heating. Another disturbance is expected to ripple along the front later tonight triggering another round of thunderstorms over northeast Illinois and a renewed expectation of flash flooding problems.

The center of this morning's rainfall was over Ogle County, the southern portions of DeKalb, Kane, DuPage, and Cook Counties, much of Kendall County, and northern portions of Grundy and Will Counties. Following are a few more rainfall totals reported:

Location       Rainfall (inches)

Oswego             4.06

Merrionette Park  3.85

Yorkville            3.83

Homer Glen      3.76

Orland Park       3.75

Lockport            3.71

Beecher            3.37

Montgomery     3.10

Naperville         3.03

Channahon       2.80

St. Charles        2.76

In Illinois, a Flash Flood Warning remains in effect until 11:30AM for areas shaded in orange.  The warning for Illinois runs along and south of Interstate 88 and includes the following counties:

Kendall, Will, most of De Kalb, most of Kane, southwest Du Page, extreme southwest Cook, northern Grundy

In Indiana, a Flash Flood Warning remains in effect until 3:30PM for most of Lake and Porter counties south of Interstate 80. 

BELOW:  Flash Flood Warning = Orange

======================================================================

Thunderstorms are developing rapidly to the north and west of Chicago the strongest area currently extends from near Lone Rock in southwest Wisconsin to near Waterloo in eastern Iowa. Tops of these thunderstorms already exceed 50,000 feet. Other strong thunderstorms have developed in the Milwaukee area and are headed east into Lake Michigan.

Active development should continue this evening as the approaching cold front impacts the energetic hot and humid air mass entrenched over the area. One inch diameter hail was  reported at Castle Rock in Grant County in southwest Wisconsin at 5:16 pm.

The Storm Prediction Center in Norman, Oklahoma has just issued severe thunderstorm watch #441 for areas just north and west of Chicago, including the counties bordering Wisconsin of Lake, McHenry, Boone and Winnebago.  While not covering the City of Chicago, the watch does include the Milwaukee and Rockford areas.

Temperatures climbed well into the 90s across the Chicago this afternoon marking the third consecutive day here where the mercury has topped 90 degrees. With gusty southwest winds temperatures throughout the area at 4pm were clustered in the middle 90s.

Some  4pm readings include O'Hare 94

                                  Midway 95

                                  Wheeling 95

                                  Northerly Island 96

                                  Gary 95

                                 Waukegan 93

Thunderstorms have been flaring up much of the day to the north across Wisconsin, but as a cold front approaches the area from the west, the Storm Prediction Center in Norman, Oklahoma is contemplating issuing severe weather watches for areas just to the north and west of the Chicago area. While the initial watch issuance may not include the city of Chicago, it is quite likely that later watches will. The entire Chicago Metro area is in the "slight risk" category for severe thunderstorms. Should severe weather develop into the Chicago area later this evening, the most likely onset would be in the 9pm-11pm time frame.

Cooler weather will move in after the thunderstorms and cold front pass with Thursday's highs expected to be in the 60s, down 30 degrees or more from today's 90s.

Early this morning low pressure was centered over Lake Superior with the associated cold front extending to the southwest through northwest Wisconsin ..southeast Minnesota..northwest Iowa into  western Kansas. A band of thunderstorms that developed ahead of the cold front over southern Wisconsin into eastern Iowa was expected to slowly weaken and finally die out as it approached the Rockford area mid-morning. As the low center tracks east, the cold front will move southeast, entering northwest Illinois this evening and slowly sagging south through the Chicago area overnight tonight.

Warm southerly flow, with winds gusting at times well over 20 mph will prevail over southeast Wisconsin, northeast Illinois and northwest Indiana today. Temperatures only fell into the upper 70s in most areas overnight, in fact readings did not drop below the 80-degree mark along Chicago's lakefront. So temperatures have a head start today and will probably warm well into the 90s with heat indices hitting 100 degrees-plus at most locations this afternoon. There will be abundant sunshine and the sun will be stationed at a high elevation overhead this afternoon - roofs/buildings/streets will retain heat making it "feel" even warmer than the 100-degree heat indices forecast, so individuals should take precautions to minimize time in the sun and stay as cool as possible.

A band of thunderstorms should develop along and ahead of the cold front later this afternoon  - probably spreading east into western portions of the Chicago metro area this evening. Very strong/severe storms will be possible with heavy downpours, damaging winds, large hail and even a chance of isolated tornadic activity. Strongest storms will probably occur before midnight.

Today is the third and final day of the first heat wave of 2011.  It should be another scorcher with heat index values near 100 degrees.  We haven't been this hot since August of 2006. 

It could be worse...

The Wallow Fire in eastern Arizona has scorched more than 300,000 acres making it the second worst wildfire in the state's history.   Smoke from the fire is being carried by southwest winds some 1000 miles downwind, all the way into Iowa.   Weather Underground's Wundermap projects that smoke to reach Illinois and Indiana today. 

  That smoke reached Minneapolis yesterday on a day that saw a record 103 degrees.  The resulting sunset had a reddish-orange glow.

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At 1PM, temperatures have soared past the 90 degree mark across most of the Chicago area.  The lone exception, shoreline areas of northern Indiana and western Michigan where a lake breeze is holding readings in the 70s and 80s this afternoon.  

Oddly, a state know for its bitter cold weather is experiencing the hottest temperatures in the Midwest.  Rochester, MN, which reached 99 degrees at 1PM, is headed for their first 100 degree reading since 1988. 

Dramatic cool down Thursday

A strong cold front coupled with a wind off Lake Michigan will result in a 40 degree temperature drop by Thursday afternoon, when readings are expected to hover in the 50s. 

BELOW: Current Temperatures