Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 261922

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

222 PM CDT

Through Wednesday...

Surface high pressure will dominate across the region through
Wednesday. This will result in light and variable winds and
seasonably cool temperatures tonight. Some fog may develop later
tonight...especially outside of the Chicago metro area as
temperatures look to cool a bit below this afternoon dew points.
Given the high will be overhead with light winds, and because some
patchy fog was reported this morning to our west under this high,
I have opted to include the mention for such in the forecast later
tonight. Any fog will be short lived and quickly dissipate with
sunrise. Another mild day is likely Wednesday with light winds and
another afternoon lake breeze. Temperatures inland could end up
another degree or two warmer than todays readings, which would
mean the potential for upper 80s highs. Closer to the lake,
however, temperatures will remain in the low 80s.

Given the lack of any organized focus, it appears the threat of
thunderstorms will be very low through early Wednesday evening.
With this in mind, I have mentioned a dry forecast through the day
on Wednesday. The better chances for storms looks to arrive by
Thursday, see more on this in the long term discussion.



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.

With the surface high overhead tonight there will be a chance for
some patchy fog late tonight, mainly at KDPA and KRFD. However, I
have left this out of the current forecast at this time as
uncertainty is high in the extent of development over these
terminals. Fortunately any fog that does develop would likely be
short lived and dissipate with sunrise.



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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