The Coming Week

Diurnal showers and thunderstorms have dissipated with sunset, and it will be partly cloudy and cool overnight. With  dew points still in the middle 50's, and low temperatures expected to reach that level or a little lower overnight there will be patchy fog later tonight in favored low lying rural areas. High pressure will settle into the area on Monday, and it will be partly sunny and delightful with a high in the low to middle 70's. Low pressure will develop over eastern Colorado on Monday night and move to Kansas City by 6 am Tuesday morning. It will be dragging a warm front eastward across western Missouri and western Arkansas. Gulf moisture will feed up and over the warm front, and to the east of the low bringing a chance of showers and thunderstorms to the Stateline Monday night. The low will move across northern Missouri on Tuesday and into central Illinois on Tuesday night. Showers and thunderstorms will overspread the Stateline on Tuesday morning, continue off and on during the afternoon, and taper to a more scattered nature as the low moves to just south of Chicago by the breakfast hour on Wednesday. Weak high pressure will take over at the surface on Wednesday as the jet stream lifts off to the northwest, and an upper level dome of high pressure builds across the eastern part of the US for the rest of the week. On Friday a warm front will stretch from northwestern Iowa across Quincy and Evansville, Indiana. There may be some scattered thunderstorms as Gulf moisture feed northward with the front. It will be very warm an humid Friday, Saturday, and Sunday with a chance of thunderstorms each day.
By Meteorologist
Eric Nefstead

Few Pop Up Rumbles Today

With the sunshine we had earlier in the day and an upper level disturbance coming in from the northwest, look for a few pop up storms to develop and move southeast this afternoon.  With any of the storms that move through gusty winds and possibly small hail can be expected. 

Weather Update this Evening

Thunderstorms continue to develop and move east this evening along a warm front and ahead of a cold front in Iowa.  As of right now, supercell thunderstorms continue to develop south along I-88 (even with a few tornado warnings) while a line of storms stretch from southern Wisconsin into east-central Iowa.  While there are no warnings associated with this line - look for heavy rain and gusty winds as they move through.  Storms will continue to develop to the south in an area that is fairly unstable.  The image on the bottom shows the CAPE values (convective available potential energy) or how much energy is in the atmosphere for the storms.  Storms will continue to develop to the south but we'll be watching the southern edge of this line as is moves across the Mississippi River for any severe development.

Severe Potential this Afternoon/Evening

Update:  Tornado Watch issued for Whiteside County until 11pm

A severe thunderstorm watch may be issued later this afternoon as storms continue to develop to the west in Iowa ahead of a warm front.  Storms in southern Wisconsin will continue to move to the northeast this afternoon so they are not of concern.  What we'll be watching through the afternoon/evening are the ones developing in Iowa and to the southwest of the Stateline along the warm front and an area of low pressure.  We will likely see an increase coverage to the west and then storms will move to the east through the evening and night, possibly developing into a cluster of storms tonight.  With any of the storms that do develop - very gusty winds, heavy rain and hail could be possible.  If any supercells develop an isolated tornado can't be ruled out, however I think that threat should reside more to the west of the Stateline.  We will continue to monitor the situation through the afternoon and update you if there is a watch issued. 

Severe Watch Over

The severe thunderstorm watch for Winnebago, Boone, DeKalb, Ogle, and Lee counties has been cancelled. Although a strong storm developed in southern Lee county earlier this evening, severe weather is no longer expected tonight. We've lost the heating of the day now, plus a line of storms that developed from southeast Iowa into western Illinois "stole" some of the instability for us today. Tomorrow we'll be watching for more storms, some of which could produce heavy downpours.  --TS

Severe Thunderstorm Watch

The entire WTVO viewing area (with the exception of Stephenson county for now) is now under a severe thunderstorm watch through 11pm. Watch-out for the development of severe storms which could include quarter-size or larger hail and 60mph or higher winds.  --TS

Update on Severe Threat

A stable layer of clouds spent much of the afternoon over the Stateline. For this reason, we've yet to see any severe weather develop. There are some breaks in the overcast now, but before too long (by mid-evening) the cold front that's already in NE Iowa will push into or just south of the area. This will give us even more stability. Plus, when the sun sets we'll lose one of our main sources of convection (storm development).

Those are the negative factors for severe weather. The positives are that we still do have a lot of instability aloft to work with for the next 2-4 hours, and storms might still fire along that front just to our west. As of now, there is a severe thunderstorm watch in effect through 11pm for areas just to our south... Including west-central Illinois.  --TS