Update: 70mph winds possible in McHenry County

545 PM CDT TUE AUG 2 2011

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT FOR NORTHERN BOONE
AND NORTHERN MCHENRY COUNTIES UNTIL 630 PM CDT...

AT 542 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DESTRUCTIVE WINDS
IN EXCESS OF 70 MPH. THESE STORMS WERE LOCATED ALONG A LINE
EXTENDING FROM LAKE GENEVA TO 5 MILES NORTH OF POPLAR GROVE...MOVING
SOUTHEAST AT 40 MPH.

LOCATIONS IMPACTED INCLUDE...
HARVARD...WONDER LAKE...WOODSTOCK...CAPRON...HEBRON AND RICHMOND.
PRECAUTIONARY/PREPAREDNESS ACTIONS...

SEVERE THUNDERSTORMS PRODUCE DAMAGING WIND IN EXCESS OF 60 MILES PER
HOUR...LARGE HAIL...DEADLY LIGHTNING...AND VERY HEAVY RAIN. FOR YOUR
PROTECTION MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF YOUR HOME
OR BUSINESS. HEAVY RAINS FLOOD ROADS QUICKLY SO DO NOT DRIVE INTO
AREAS WHERE WATER COVERS THE ROAD.

Severe T'Storm Watch

THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH
719 IN EFFECT UNTIL 1 AM CDT /2 AM EDT/ WEDNESDAY FOR THE
FOLLOWING AREAS
IN NORTH CENTRAL ILLINOIS

BOONE DE KALB LA SALLE
LEE OGLE WINNEBAGO MCHENRY

Stronger storms possible later this afternoon/evening

HIT REFRESH FOR THE LATEST WEATHER INFORMATION

6:40pm:  Storms continue to move east out of the viewing area this evening.  A few more could redevelop later this evening

A Severe Thunderstorm Warning continues for Rock and Walworth counties until 6:15pm.

A Severe Thunderstorm Warning has been issued for Boone and McHenry counties until 6:30pm

These storms are capable of producing ping pong sized hail and gusty winds.  They're currently moving to the east around 25mph.



3:45pm Update:  The atmosphere remains fairly capped and storms would likely have a hard developing ahead of the cold front that currently sits back in central Iowa.  That's probably why a watch hasn't been issued just yet.  As the front moves southeast the cap should weaken and that should help to get storms to fire.  Keep a watchful eye to the sky heading into this evening because storms should develop within the next couple of hours but should be out of our area by 11pm.

1:00pm Update:  Southern Wisconsin and northern Illinois will likely be placed under a Severe Weather Watch later this afternoon.  Instability continues to build south of the warm front and ahead of a cold front now in central Iowa.  Storms will likely develop ahead of this front within the next couple of hours and move east.

12:00am Update: The slight risk for strong to severe thunderstorms is still there as a cold front moves in from the northwest.  While most of this afternoon will remain dry due to a fairly strong cap in place I do anticipate storms to fire up across west-central Wisconsin around 3pm or so and move southeast with the front.  Because of that I am watching the time frame of 4pm to 9pm for storms to roll through.  There is still a bit of question as to just the exact coverage of the storms, however.  The top image is the NWS WRF weather model at 7pm and it has storms developing across southern Wisconsin during that time.  As the front moves closer the cap along with the CIN (Convective INhibition) is forecast to weaken.

 A couple of outflow boundaries across southern Wisconsin could interact with that cold front and cause a few storms to rotate.  After about 11pm I expect any storms to be east of the Stateline.

The cloud cover from the storms across central Wisconsin earlier this morning will keep our sunshine filtered as we go throughout the day.  The heat and humidity will continue to build across the area behind a warm front currently moving through Wisconsin.  A cold front stretching through western Minnesota will be the focus for our storm development as we go later into the afternoon and evening.

The Storm Prediction Center has the area under a slight risk for strong to severe thunderstorms as that cold front approaches.  Our atmosphere will remain capped (warm air above won't allow air at the surface to rise) through a good portion of the day and it likely won't be until the front moves closer, after 4pm, that we will see storms start to form.  The area that we'll be watching for possible storm development will be across southwest Wisconsin and northeast Iowa ahead of the cold front, but also along any old outflow boundaries.  As storms form they'll move southeast into our area between the 4pm - 8pm time frame.  While the main threat from the storms would be damaging wind gusts, an isolated tornado can't be ruled out given the potential of any interaction between the cold front and those old outflow boundaries.

Same story, just a different day

A Heat Advisory will continue through this evening ahead of a cold front that will move through later tonight.  With the filtered sunshine this morning temperatures have only reached the low 80s.  However, when you factor in the lower 70 dew points it feels a lot warmer.  Because of that the advisory will continue.  I anticipate temperatures to reach the low to mid 90s this afternoon. 

A cold front coming through will put an end to the humidity, but bring with it the potential for strong to severe thunderstorms later this afternoon.

Weather watch may be issued soon for some

8:00am Update:  Storms in Wisconsin have been having a hard time making much progress to the south so far this morning.  As a result, I'm not too concerned about any storm potential for our eastern counties this morning.  A greater threat for storms will be with a cold front later this afternoon and evening.

Ongoing thunderstorms in central Wisconsin this morning will continue to move southeast along a warm front that extends through southeast Wisconsin and northeast Illinois.  A severe thunderstorm watch currently is in place across central Wisconsin and may need to be extended further south later this morning should the storms keep their strength.

Tropical Storm Emily

Tropical Storm Emily has formed in the waters of the Carribean Sea, about 350 miles to the southeast of San Juan, Puerto Rico. It has 40 mph maximum sustained winds, and is moving toward the west at 17 mph.

The government of Barbados has issued a tropical storm warning for Dominica. There is also a tropical storm warning out for Puerto Rico and the islands of Vieques and Culebra, and a tropical storm watch for the U.S. Virgin Islands. Emily will turn more to the west/northwest over the next 24 hours and could impact the Bahamas and Florida by the weekend. There are several islands between it's current position and Florida, which should impede its strengthening.

Heat and Humidity to Start Off the Week

**There is a Heat Advisory in-effect for Stephenson, Jo Daviess, Carroll, and Whiteside counties until 10pm Tuesday.** High pressure located over Illinois today will keep tranquil weather in the forecast. However, it will remain humid with no fronts or other weather features to kick the humidity from our recent rains out of the lower atmosphere. It will be partly cloudy, hot, and humid with a high near 91 along with an afternoon heat index reaching near 100. The heat and humidity will intensify tomorrow with temperatures approaching the middle 90's, and heat indexes as high as 105 in he Rockford area, and up to 109 around Freeport.  A cool front will approach the area by late afternoon along some thunderstorms that may last into the evening. The Storms Prediction Center has our region under a slight risk of severe thunderstorms tomorrow afternoon and evening.  Cooler and drier air will move into  northern Illinois on Wednesday with the high temperature dropping back into the middle 80's on Wednesday under mostly sunny skies.  The air conditioners will get a break during the night time hours later in the week with overnight lows dropping back into the 60's. The cool front will stall out as a stationary front across southern Illinois late Wednesday, and lift a little northward on Thursday, Thursday night, and Friday with waves of low pressure moving along it, showers and thunderstorms could feed back across the Stateline Thursday night through Friday evening.