Thanks to Saturday morning’s showers and considerable cloudiness, a stable atmosphere was in place over northern Illinois and southern Wisconsin for much of the afternoon.  As a cool front pushes toward the area, though, thunderstorms will develop ahead of this boundary for the evening and nighttime hours.  The thunderstorms will be scattered in nature.

Looking at the latest trends, the best threat for any severe weather appears to stay just south of our area.  However, we may see a stronger thunderstorm or two across some of our thirteen counties.  The stronger storms will contain heavy rain, small hail, frequent lightning, and brief gusty wind.

The scattered thunderstorm activity will wind down after midnight, allowing for some breaks in the cloud cover.  Patchy fog may develop toward dawn.  It looks like we’ll sneak out a dry day on Sunday, with much of the stormy activity confined to central Illinois and points south.  We can’t rule out a widely-isolated thunderstorm, especially south of Interstate 88.

-Joe

Posted under Exactrack|HD, rain, severe weather, Threatrack, weather

Severe thunderstorms moved through eastern Iowa, northern Illinois and southern Wisconsin on Wednesday.  A few tornadoes touched down, including one which tracked through southern Jo Daviess and Carroll County.  There were also a few storms with unconfirmed tornado reports; those reports will be verified by the National Weather Service over the next couple of days.

The National Weather Service (NWS) Office in Romeoville, Illinois—which serves parts of our area—plans to conduct a storm damage survey today.  NWS employees will travel to southeastern Lee and southern DeKalb County, as well as nearby Kendall County.  On Wednesday afternoon, a severe thunderstorm moved through the Paw Paw, Shabbona, Somonauk and Yorkville areas, causing widespread wind damage.  Photos and even a few videos of the event seem to suggest a tornado caused some of the damage.  Toppled trees and power poles as well as damage to a few grain bins were initially reported.  A video of the possible tornado near Paw Paw was posted on the weather blog; you can find it HERE. 

The NWS employees will assess the damage and determine if a tornado did indeed touch down or if strong, straight-line winds are to blame.  We will let you know the outcome as soon as we know.

-Joe

Posted under photos, severe weather, tornado, weather

11:30PM – Severe storm threat has ended.

(10:27:02 PM) nwsbot: LOT issues Severe Thunderstorm Warning [wind: 60 MPH, hail: 1.00 IN] for De Kalb, Kendall, La Salle, Lee [IL] till 11:30 PM CDT

Update from NWS: …DAMAGE SURVEY TO BE CONDUCTED THURSDAY…

THE NATIONAL WEATHER SERVICE WILL BE DEPLOYING A DAMAGE ASSESSMENT
TEAM ON THURSDAY TO PORTIONS OF EASTERN LEE…FAR SOUTHERN
DEKALB…AND KENDALL COUNTIES. THE TEAM WILL BE INVESTIGATING A
CORRIDOR FROM PAW PAW AND SHABONNA EASTWARD TOWARD PLANO AND
YORKVILLE. THERE WERE SCATTERED REPORTS OF FUNNEL
CLOUDS…TORNADOES…AND SOME DAMAGE OVER THIS AREA.

OTHER AREAS OF DAMAGE OR UNCONFIRMED TORNADO REPORTS MAY BE
INVESTIGATED AS WELL. MORE INFORMATION WILL BE PROVIDED THURSDAY
MORNING.

(7:33:47 PM) nwsbot: Local Storm Report by NWS LOT: Shabbona [Dekalb Co, IL] park/forest srvc reports TSTM WND DMG at 04:35 PM CDT — shabbona lake state park boats tossed onto boats. large trees snapped at trunk or uprooted. power poles down near state park office.

Stormchasers got video of a tornado in Paw Paw, IL in Lee Co.

(6:55:53 PM) nwsbot: Local Storm Report by NWS DVN: 2 S Hanover [Xxx Co, XX] law enforcement reports TORNADO at 06:51 PM CDT — moving southeast.
(6:55:53 PM) nwsbot: Local Storm Report by NWS DVN: Hanover [Jo Daviess Co, IL] trained spotter reports TORNADO at 06:51 PM CDT — moving southeast.

(6:47:16 PM) nwsbot: DVN issues Tornado Warning [tornado: RADAR INDICATED] for Carroll, Jo Daviess [IL] till 7:15 PM CDT …AT 641 PM CDT…A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO WAS LOCATED NEAR HANOVER…AND MOVING SOUTHEAST AT 30 MPH.

(6:02:29 PM) nwsbot: DVN issues Tornado Warning [tornado: RADAR INDICATED, hail: <.75 IN] for Jo Daviess [IL] till 6:30 PM CDT …AT 559 PM CDT…A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO WAS LOCATED NEAR MENOMINEE…AND MOVING SOUTHEAST AT 20 MPH.

(3:43:45 PM) nwsbot: LOT issues Tornado Warning [tornado: RADAR INDICATED, hail: 1.25 IN] for Lee, Ogle [IL] till 4:30 PM CDT …AT 342 PM…A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO WAS LOCATED NEAR WALTON…AND MOVING NORTHEAST AT 35 MPH.

(3:34:19 PM) nwsbot: LOT issues Severe Thunderstorm Warning [wind: 60 MPH, hail: 1.25 IN] for Lee, Ogle [IL] till 4:30 PM CDT

A Tornado Watch is in effect through 9pm. This is a particularly dangerous situation! Storms will affect the Rockford Metro between 4-8pm. -Eric

Posted under severe weather

If you haven’t read through Chief Meteorologist Eric Sorensen’s Tuesday blog post regarding our severe weather threat for Wednesday afternoon, I’d recommend it. You can find his blog post HERE. 

A somewhat stable airmass is in place across the Stateline for Wednesday morning.  Overnight showers and thunderstorms in western Iowa fizzled out before they crossed the Mississippi River into Illinois.  The result is a mostly cloudy morning with a few breaks of sunshine.  Humidity and temperatures will be on the rise throughout the day, with highs expected to reach the middle 80s.

The meteorological ‘ingredients,’ so to speak, are coming together for severe weather later today.  With a surface wind still expected out of the southeast and an upper-atmospheric wind out of the south-southwest, directional wind shear and storm rotation will be a concern this afternoon and evening.  A warm front is still expected to lift into northern Illinois this afternoon, at least as far north as the Interstate 88 corridor.  It is along this front that supercell thunderstorms may develop.  Supercell thunderstorms have the potential to produce strong wind gusts, large damaging hail, and possibly a tornado.  These threats will all be of local concern this afternoon, including torrential rain.

Don’t panic.  However, today is a good day to be ‘weather aware’ and keep an ‘eye on the sky.’  Make sure you have a severe weather safety plan in place.  We haven’t seen a threat like this across the Stateline for a few years.  Let’s plan for the worst and hope for the best.

As far as timing goes, our array of forecasting products are not on the exact same page. However, the best timeframe for severe thunderstorms to develop is this afternoon and evening.  Storms may begin to form in eastern Iowa around 2pm through 4pm and move east-southeast into our area after that.  Some model solutions begin a bit earlier, some begin later around dinner time.  We do know that this afternoon and evening will be active. 

Don’t forget, you can track the storms on your smart phone with our 13 Weather Authority App or sign up for severe weather text alerts.

-Joe

Posted under rain, safety, severe weather, Threatrack, tornado, weather, Wind

The set up for severe weather Wednesday afternoon is quite ominous. The following forecast is solely based on our Futuretrack model. Other models depict slight shifts north and south. So, while we can pinpoint exact locations of possible severe weather using this model, keep in mind it is just one model solution! We’ll have to forecast as we go through the day on Wednesday to get the exact particulars and locations effected.

Having said that, this is the forecast model I am going with right now. Before I get into the nuts and bolts, please know that a lot depends on the amount of instability available. (In my previous blog post, you can see how distinct the cut-off of instability is. This map shows how we go from a completely charged atmosphere to nothing is. Unfortunately, it’s an all-or-nothing scenario.)

First, let’s look at the surface wind directions. It’s obvious here we’ll have an east-to-west front lying right over Northern Illinois with plenty of convergence along the front (which promotes ascent). Areas north of the front will be slightly more stable, but areas south of the front will yield plenty of instability! Concerning to us is the area where there is a southeastly wind. This usually takes place along and immediately south of the frontal boundary. Clinton, IA, Sterling-Rock Falls, Dixon, DeKalb, Mendota, and the southwest suburbs of Chicago all lie in this sweet spot. (Again, keep in mind, this is one model and this boundary may set up a few miles north or south of there…causing this sweet spot to shift some.)

But we have to think of the atmosphere in three-dimensions. Simply looking at the surface wind gives us no clues as to the potential severity of the storms Wednesday afternoon. In this graphic, I superimposed the wind at 3,000 feet. They are noted as colored lines. The brighter (reds and pinks) indicate stronger wind aloft. Note, that is in Central Illinois. There, we can see quite a bit of “speed shear” which is a form of wind shear where wind increases with height. This set up will bring about the possibility of significant straight-line wind potential for Central Illinois…and Indiana later in the day. Closer to home, the wind over Northern Illinois is much lighter at 3,000 feet, but is moving perpendicular (or at a right angle) to the southeasterly wind. This maximizes the amount of wind shear over North Central Illinois. With that 90° change in wind direction: from southeast at the surface to southwest at 3K feet, I believe this is the area at highest risk for isolated tornadoes on Wednesday afternoon. You can see where the low pressure center is in Central Iowa around 6pm with the warm front extending eastward through Northwest Illinois and then toward the southern end of Lake Michigan. The storm motion tomorrow will be from west to east with a slight movement toward the southeast later in the day. The highest threat for severe weather will exist between 3-8pm.

Be alert for changing weather and have a way to get warning information, whether that’s from the WREX Weather App (Search on the App/Google Play stores) or a NOAA Weather Radio.

Meteorologist Joe Astolfi will be updating the blog first thing Wednesday morning. -Eric

Posted under severe weather

Get ready for more big thunderstorms! A few of you saw hail and heavy rain Tuesday afternoon, especially across Ogle and DeKalb County. This shot taken from near Creston around 3pm.

Our attention will shift to the possibility of thunderstorms during the wee hours of Wednesday and then again in the afternoon. There are indications, an MCS will develop in northwestern Iowa around midnight, tracking east-southeast into the Illinois/Wisconsin stateline area during the pre-dawn hours. This storm will have the potential to produce damaging wind and torrential rain.

We’ll probably get a decent break in the rain for lunchtime with storms refiring for the late-afternoon. Storms will have the potential to produce large hail, damaging wind, and isolated tornadoes. This graphic shows where the atmospheric energy will be at its max (shaded regions). A strong “vort-max” or disturbance will be moving into our region from the northwest. This increases my confidence of thunderstorms to about 90%.

Please be weather-aware on Wednesday! -Eric

Posted under severe weather

Severe thunderstorms are a good bet across parts of South Dakota, southern Minnesota and northwestern Iowa late Tuesday. In fact, the Storm Prediction Center has placed that region in a Moderate Risk (a category that is not issued very often).  Should these storms hold together, there is the potential for a derecho to develop. “Derecho” is a meteorological term derived from the Spanish language word for “straight.”  It refers to a widespread and rapidly-moving wind-storm associated with a bow-echo line of thunderstorms that can last hours and overnight. Straight line winds over 80mph can produce damage across areas hundreds of miles long and more than 100 miles wide.  Typical derecho events see a southeasterly turn in the progression of the line of storms.  However—and I cannot stress this enough—derecho events are extremely difficult to forecast until they have formed.  This will need to be monitored locally as we head into the overnight hours (pre-dawn hours of Wednesday).

Severe thunderstorms are a possibility again on Wednesday. A round of showers and thunderstorms in the early morning may yield a break during the middle part of the day.  By the afternoon and evening a warm front will lift north toward the Stateline. If we get enough daytime heating, our atmosphere will destabilize and showers and thunderstorms will form.  Some of these storms may take on supercell form, which could produce large hail, heavy rain, strong wind gusts, and an isolated tornado.  Perhaps the highest threat will be just southeast of us from Chicago south to Champaign and east through Indiana and western Ohio. 

This blog post is not meant to scare; it’s meant to inform you of the possibility of severe weather.  Not all of us will be affected; however, the threat exists across our entire region.  It’s a great time to be weather aware!  Join 13 Weather Authority Chief Meteorologist Eric Sorensen at 5, 6, and 10pm tonight for further forecast updates and analysis.

-Joe

Posted under safety, severe weather, Threatrack, weather, Wind

Brace yourselves. Clouds and rain are in the forecast….again!  If you thought it’s been cloudy and rainy lately, you are correct.  Looking at the past 30 days, there have been 21 days with at least a trace of rain reported at Chicago Rockford International Airport! 

Sunday will start off mostly cloudy and mainly dry, with just a few isolated showers dotting the radar.  Scattered showers and thunderstorms will become more numerous as we head into the afternoon and evening hours.  A breezy south wind, 10-20mph, will help temperatures rise to near 75 despite the clouds.

This system that is headed our way for Sunday brought severe weather to the Great Plains on Saturday.  While the chance for severe weather is low locally, there is a minimal threat for a few stronger thunderstorms Sunday afternoon. I anticipate the best threat of severe weather to stay just south of our local area, affecting Bloomington, Peoria, Springfield, and St. Louis. 

The showery, thundery weather will continue Sunday night as well.  As the system pushes off to our east, a few lingering scattered showers will remain in the forecast through Monday afternoon. 

-Joe

Posted under FutureTrack, rain, severe weather, Threatrack, weather

Today, we got quite a few reports of “possible tornadoes” including one spotted by several law enforcement officials in Whiteside Co. The National Weather Service Forecast Office in Davenport will be looking at any damage there on Friday, in order to determine what kind of damage was done there.

In the meantime, we received quite a few unconfirmed reports of tornadoes in Ogle County. After examination of storm photos, this was not a tornado…but a gustnado. What’s that you say? Let’s go in-depth.

 First let’s look at this example of a tornado. The storm is moving from left to right so picture yourself looking north into the storm.
More often than not, a severe storm with a tornado will produce heavy rain and hail with strong, gusty wind coming down from high within the storm. Then, once the rain and hail comes to an end, a tornado will exist at the bottom of the storm’s updraft. Finally, as the storm moves from left to right the rear-flank downdraft (often called the RFD) comes in to produce additional wind damage.

So that’s a tornado…most likely NOT what we had tonight.

Instead, let’s look at the diagram of a gustnado. Again, the storm is moving from left to right. Instead of the rain and hail coming first, a swirling vortex is seen BEFORE the storm. In all of the photos I’ve observed today, this vortex was not attached to the storm iteself. Instead, the wind moving out on the front side of the storm began swirling and created a gustnado (in short, a tornado on the gust front).

After seeing photos of the gustnado and hearing reports, it’s likely this was a strong one tonight! Trees and power lines were taken down in its path…and if a survey team assesses the damage, it’s likely to be classified as a gustnado with a rating on the Enhanced-Fujita Scale (the scale used to rate tornadoes).

Posted under severe weather, weather geek

This video from Chad Toye of some dirt and dust spinning up on the frontside of the thunderstorms near Roscoe, IL

(5:36:59 PM) nwsbot: MKX issues Severe Thunderstorm Warning [wind: 70 MPH, hail: <.75 IN] for Green, Iowa, Lafayette [WI] till 6:30 PM CDT

(5:32:36 PM) nwsbot: DVN issues Tornado Warning [tornado: RADAR INDICATED, hail: <.75 IN] for Henry, Whiteside [IL] till 6:00 PM CDT …AT 527 PM CDT…A SEVERE SQUALL LINE CAPABLE OF PRODUCING TORNADOES THAT MAY NOT BE VISIBLE DUE TO HEAVY RAIN WAS LOCATED NEAR ERIE… AND MOVING NORTHEAST AT 50 MPH.

(5:23:58 PM) nwsbot: DVN issues Severe Thunderstorm Warning [wind: 60 MPH, hail: <.75 IN] for Clinton, Delaware, Dubuque, Jackson [IA] and Carroll, Jo Daviess, Stephenson, Whiteside [IL] till 6:30 PM CDT

5:25PM – Severe storms have moved through the Quad Cities on their way toward Northern Illinois and the Rockford Metro. Extensive damage has been reported along the line with large trees and power lines taken down, as well as a roof blown off a home in Augusta, Illinois, south of Macomb. Please take this storm seriously! It has a history of producing damage. Stay indoors, away from windows if the storm approaches your area. In addition, a Tornado Watch remains in effect. Severe storms occasionally produce tornadoes with little advance warning. -Eric

4:47pm – Quarter sized hail in Lena, IL. Storm now between Winslow, IL and Monroe, WI…headed northeast. -Eric

(4:36:52 PM) nwsbot: Local Storm Report by NWS DVN: 2 NNW Lena [Stephenson Co, IL] trained spotter reports HAIL of pea size (E0.25 INCH) at 04:36 PM CDT —

4:25pm – Severe thunderstorms headed toward Aurora, IL right now just skimming southeastern DeKalb Co. The main threat for us in Northern Illinois will be from the squall line coming in from the Quad Cities area. -Eric

(4:16:31 PM) nwsbot: LOT issues Severe Thunderstorm Warning [wind: 60 MPH, hail: 1.25 IN] for De Kalb, Grundy, Kane, Kendall, La Salle, Will [IL] till 5:15 PM CDT

2:30pm update – Storm over Lee County is severe. There is no rotation with the storm right now, but it remains dangerous as it heads toward Dixon. Remain indoors, away from windows, ready to get into the basement if you live in Dixon. -Eric

(2:16:29 PM) nwsbot: DVN issues Tornado Warning [tornado: RADAR INDICATED, hail: 1.00 IN] for Dubuque [IA] till 2:45 PM CDT …AT 213 PM CDT…A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO WAS LOCATED NEAR CENTRALIA…AND MOVING NORTHEAST AT 45 MPH.

2:10pm update – A developing severe storm is located in Bureau County, headed into Lee County. Large hail to the size of quarters is likely with this storm. If you are in Amboy or Dixon, be prepared for severe weather. As this storm matures, it could produce a tornado within the next hour or so. Be ready for changing weather! -Eric

(2:01:57 PM) nwsbot: DVN continues Severe Thunderstorm Warning [wind: 60 MPH, hail: 1.00 IN] for Bureau [IL] till 2:30 PM CDT

(11:57 AM) nwsbot: MKX issues Tornado Watch for Green, Rock [WI] till 7:00 PM CDT

(12:34 PM) nwsbot: LOT issues Tornado Watch for Boone, De Kalb, Lee,  Ogle, Winnebago [IL] till 8:00 PM CDT

Posted under severe weather, tornado, weather