Monday, August 20, 2018

Monday Evening Weather Update

Heavy rain producing thunderstorms continue to lift north into Wisconsin Monday evening.  While the overall severe threat remains low, the heavy rain threat is still pretty high - especially with storms lifting into southwest Wisconsin.

The majority of the heavy rain, and flooding, has been occurring in Wisconsin but I did receive a report of nearly four inches of rain in Orangeville.  Thunderstorms passing north of Rockford will continue to lift north into Wisconsin, with more widely scattered activity during the overnight.  Low pressure currently moving through southeast Iowa will pass over northern Illinois tonight before shifting east by Tuesday morning.

Monday Update

A Flash Flood Watch has been issued for Green and Rock counties in southern Wisconsin, through 9am Tuesday. This area has already been battered by several rounds of heavy rain late last week, and with the potential for more heavy rain this afternoon and evening some localized flooding  will be possible.

Heavy rain is currently falling near Amboy and through portions of Carroll and Jo Daviess counties, and will continue to lift northward. there hasn't been much lightning detected, but you'll want to watch for ponding on some area roads. This first wave of rain will move out of the area this afternoon, but behind it we will need to keep an eye on any potential clearing of the cloud cover. If we get the sun to mix out the clouds, it could allow for enough destabilization to occur which would lead to more instability. If we get enough instability then this could prompt a few stronger storms for portions of the Stateline area this afternoon. If the warm front lifts far enough north, then it is also possible for a spin up weak tornado or two. The atmospheric conditions however aren't conducive for any long lived strong tornadoes. The threat for heavy rain will continue into the afternoon and evening, with many receiving .25" to .75" inches of rain, though some localized higher totals are possible.

The coverage of showers and storms will decrease tonight into Tuesday, though can't rule out a few showers and storms Tuesday afternoon.

Sunday, August 19, 2018

Storm threat increases Monday - Severe threat not that far away

A strong area of low pressure to the west will bring an increasing chance for thunderstorms Monday afternoon and evening.

Showers and thunderstorms have been ongoing over the Plains as low pressure moves into northern Missouri.  Severe weather has been occurring in parts of Missouri and Arkansas Sunday evening, and will remain well south Sunday night.

As a warm front lifts closer to northern Illinois Monday morning, showers and embedded thunderstorms will increase in coverage from southwest to northeast between 7am and 10am, overspreading much of northern Illinois by Noon.  A break from the rain and storms may occur early afternoon, also allowing for a brief break in cloud cover.  If clearing is significant enough, instability will rise causing a higher threat for storms - some strong to severe - by the afternoon and evening.

As of Sunday night it looks like the greatest threat for severe weather will occur over central Illinois.  But a warm front lifting close to the I-80 and I-88 corridors could bring the threat for strong to severe storms northward.  If that occurs supercell thunderstorms may form increasing the chance for large hail, but also an increased threat for isolated tornadoes right along the warm front.

Thunderstorms will remain scattered throughout Monday night, before becoming more isolated by Tuesday morning.

Friday, August 17, 2018

More Widespread Rain Followed by Brief Cool Down

Following heavy rainfall Thursday night, the majority of Friday afternoon and evening remained dry.  As skies clear out following the passage of low pressure, locally dense fog will be possible by Saturday morning.

High pressure will move in Saturday and Sunday, leaving skies mostly dry and partly cloudy.  A weak disturbance moving through the jet stream Saturday may be just enough to generate an isolated shower Saturday afternoon, but most should remain dry.  Highs both days will warm into the low to mid 80's.

Low pressure will quickly move in from the southwest late Sunday night and throughout the day Monday.  Increasing moisture will allow rain to develop as early as Monday morning, but likely become more widespread by the afternoon and evening.  Heavy rainfall will be possible during that time, with potentially another one to two inches of rain falling across the Midwest.  But the track of the heaviest rain will depend on the exact track of the low pressure system.  Either way it looks to be a soggy start for kids heading back to school Monday.

Following the passage of the low Tuesday, winds will increase from the North Tuesday, pulling down a slightly cooler air mass for the middle of the week.  Temperatures won't be terribly chilly, but highs in the mid to upper 70's will be possible with overnight lows dropping back into the 50's.  It'll be nice to turn off the A/C and let a little fresh air inside.  The cool down is short-lived because it looks like temperatures will warm back into the 80's by the end of next week.

Thursday, August 16, 2018

Thursday Evening Weather Update

A Flash Flood Warning has been issued for northeast Rock County until 3:15am Friday.  Several roads in Milton have been reported closed or impassable due to flooding.  Up to three inches of rain has fallen in that area, with an additional one to two inches possible.

 Flood Advisory remains in effect for northeast Rock County until 1:15am and for western Rock and Green counties until 11:30pm.  Flooding has been reported around Edgerton, WI with street flooding throughout town.

Showers and isolated thunderstorms have increased in coverage late Thursday afternoon as low pressure moves closer to northern Illinois.  Widespread rain and thunderstorms have been ongoing over Wisconsin and Iowa, closer tied to the low pressure system.

Not everyone will experience the rain Thursday evening, and several locations could end up dry but where the rain does fall, heavy downpours will be possible.

There is a risk for stronger thunderstorms, mostly along Whiteside and southern Lee counties where stronger thunderstorms could produce gusty winds.  But a higher threat remains further downstate.  In fact, there was a Tornado Warning southwest of Peoria earlier Thursday evening.

As the low passes northern Illinois Thursday night showers will remain possible into Friday morning.  Fog will also be possible again for the commute.  As the low moves a little further to the east during the day Friday, isolated showers and thunderstorms will develop with the heating of the day.  Drier air with high pressure arrives by Friday night which will help clear our skies for the weekend.

Foggy Commute Thursday Morning

You'll need the low beams on and to take is slow this morning! A Dense Fog Advisory is in place for the majority of northern Illinois and southern Wisconsin, as visibility drops to near a quarter of a mile for many across the area. Visibility can change quickly as you drive, so you'll want to take it slow this morning, especially in outlying and low lying areas.

 Some visibility dropping to just a few hundred feet! Low beams are a must, and make sure to not use high beams, because they will hit the fog and reflect back. The fog should begin to burn away by 9am with more sunshine.

Sunday, August 12, 2018

Widespread Rainfall Possible MidWeek

Very isolated showers developed Sunday afternoon along a surface boundary.  The rain didn't amount to much, but did bring quick downpours and even a few funnel clouds over DeKalb County.

Showers still linger over Lee County Sunday evening as a hazy sunset begins.  A little more haze and smoke was seen Sunday afternoon in Wisconsin and Illinois from the wildfires burning in Canada and along the west coast of the U.S.  Actually, quite a bit of the country is experiencing hazy skies Sunday and will likely continue to do so through Monday evening.

An isolated shower can't be ruled out Monday afternoon, but Monday should be a carbon copy of what we experienced Sunday with hazy, warm skies with temperatures in the mid and upper 80's.  Tuesday will be dry, but an incoming low pressure
system will bring widespread and heavy rainfall over the central and southern Plains Tuesday afternoon.  Much of that area is experiencing significant to exceptional drought conditions, and the increase in heavy rain could lead to flooding issues over the next couple of days.

As the low moves into Missouri and Illinois by Wednesday, moisture will be pulled northward.  A warm front will lift into northern Illinois late Tuesday night and remain just to the south during the afternoon Wednesday.  Scattered showers will be likely as early as Tuesday evening, but most likely by Wednesday morning.  Depending on exactly where the boundary ends up, widespread rain could fall over northern Illinois through Wednesday night.  Rainfall totals of half an inch, up to an inch are possible.  Isolated showers and thunderstorms will be possible Thursday, with isolated showers potentially lingering into the weekend.