Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 261707

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1207 PM CDT TUE JUL 26 2016

332 AM CDT

Through Wednesday...

Progressive westerly flow aloft will continue today, but with
surface high pressure in place expect just some afternoon cumulus
development today and some passing high clouds. Highs again will
reach the mid to upper 80s with the lake breeze keeping conditions
slightly cooler lakeside.

A cold front across the Canadian/U.S. Border will move southeast tonight
into Wednesday, reaching Central Wisconsin and adjacent Lake
Michigan late Wednesday afternoon. An upper level disturbance
across the Northern Rockies looks to trigger showers and
thunderstorms across the plains, and also across Wisconsin closer
to the cold front where a weak to modestly unstable atmosphere
will exist. Locally, surface high pressure will still hold, and
thus expecting somewhat of a repeat on Wednesday, with the
exception being increased clouds, and possibly a shower or
isolated storm sneaking into Northern Illinois late in the day.

The cold front, aided by the frictionless lake, will move into the
area Wednesday night. The aforementioned upper level disturbance
will move east across the boundary during this time, possibly
leading to a few showers and thunderstorms during the evening time
frame, with areas north of I-88 favored as the upper forcing will
mainly move east through Wisconsin.



332 AM CDT

Thursday through Monday...

Cooler conditions will be the rule Thursday through the upcoming
weekend, and there could be a few periods of showers and isolated
storms Thursday through Saturday as broad upper troughing takes
hold of the region. Gradual drying out and warming will ensue into
early next week as an upper ridge restrengthens across the Corn



For the 18Z TAFs...

No weather concerns are expected through the period as high
pressure dominates over the area. A SCT to BKN deck of VFR fair
weather CU clouds will likely continue to develop ahead of a lake
breeze this afternoon. Otherwise, easterly winds are expected
this afternoon and again on Wednesday, though wind speeds should
primarily be under 10 KT.



252 AM CDT

High pressure currently over Iowa shifts east today. Onshore flow is
expected across the southern end of the lake while winds will be
southwest at 10-20 kt over the northern end.  Winds veer and
diminish into Wednesday morning. A cold front pushes down the
lake Wednesday, and winds become north and northeast behind it.
Guidance suggests winds may increase to 10-20 kt along the front
Wednesday night. The pressure gradient tightens over the lake
Thursday afternoon as low pressure shifts northeast over IL.
Northeast winds will increase to 10-20 kt Thursday afternoon and
night. The low passes south of the lake Thursday night through
Friday morning. Winds remain northeast through Saturday and then
become south or southeast as another high pressure system spreads
over the lake over the weekend.






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