Wednesday, July 19, 2017

Severe Weather Threat Wednesday Evening

Thunderstorms moving through west-central Wisconsin are currently moving southeast and could reaching southern Wisconsin and northern Illinois around sunrise Thursday.  While the severe weather threat is low - strong winds, hail and heavy rainfall are possible.  Heads up for the morning commute.

A 'wake low' has developed over southern Wisconsin along the back edge of thunderstorms.  This is not severe, however, wind gusts to 50 mph are possible which, with the recent heavy rain, could knock down a few branches or trees.

9:30pm Update: Severe Thunderstorm Watches being cancelled for Jo Daviess, Stephenson, Whiteside.  Severe Thunderstorm Warning being cancelled for McHenry county.  Still some heavy to torrential rainfall in eastern McHenry county.

9:02pm Update: The line of thunderstorms now moving through McHenry and Walworth counties, and exiting DeKalb counties.  Winds still being reported at 70mph, with one report of penny-sized hail in DeKalb.  Heavy rainfall behind the leading edge.

8:20pm Update: Tornado Warning issued for Boone, De Kalb, Ogle, and Winnebago counties until 8:45pm.  Multiple reports of wind damage with trees and power lines downed. Radar indicated 70 mph in this line of storms. 

7:30pm Update: Severe Thunderstorm Warning issued for Winnebago and Ogle counties until 8:15pm.  Damaging winds are expected with this line as 70 mph wind gusts are possible, with reports of 66 mph wind gusts already.  Storms are moving southeast at around 65mph

6:50pm Update: Severe Thunderstorm Warning for Stephenson, Carroll and Jo Daviess counties until 8pm.  Line of thunderstorms moving into northwest Illinois has had a history of producing wind damage.  As storm moves in, remain indoors and away from winds.  Wind gusts to 70 mph are possible.  Storm is currently located over Platteville, Wi and moving southeast at 60 mph.

5:45pm Update: New Severe Thunderstorm Watch issued for southern Wisconsin and northern Illinois until Midnight.

A cluster of thunderstorms has maintained its strengthen moving out of the northern Plains and into the Midwest Tuesday afternoon.  Most of the early evening over southern Wisconsin and northern Illinois will remain dry, just very humid.  Thunderstorms are expected to move into southwest Wisconsin and northern Illinois between 8pm and 10pm and then through north-central and northeast Illinois between 9pm and midnight.  Damaging winds will be the biggest threat, followed by heavy rainfall, hail and even a low end tornado risk.

The thunderstorms are following a boundary from the Plains into the western Great Lakes.  South of the boundary and extremely unstable air mass has developed.  North of the boundary there is a little more of a stable air mass.  A second round of thunderstorms is then expected to develop back over the northern Plains late this evening, moving east into central Wisconsin by Thursday morning.  The southern edge of these storms could clip southern Wisconsin and far northern Illinois, posing another wind and heavy rain risk between 5am and 8am.

Remain 'weather aware' this evening, because there will likely be a new weather watch coming out soon for parts of the Stateline.

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