Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 121102

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
602 AM CDT Wed Aug 12 2020

212 AM CDT

Through Thursday...

A tranquil short term forecast continues to be welcomed by many
after Monday`s derecho. Surface high pressure of 1019 mb is
centered directly over northern Illinois and northwest Indiana
this morning allowing for lake breeze development by noon. Highs
will inch up a couple degrees from yesterday, with morning cirrus
in the southern and eastern forecast area giving way to a sunny
sky area wide. Dew points could mix into the upper 40s in some
parts of the area making for pleasant conditions all around.

This continues into Thursday with the area remaining well north
of a slow-moving upper low and under weak upper ridging. The
surface high pressure will be just east of the area, again
allowing for a lake breeze but with minimal cooling. Highs should
add a degree or so from today with patchy cumulus more favored.



300 AM CDT

Thursday night through Tuesday...

The strong ridge across the Upper Great Lakes over the next two
days will begin to weaken by Friday while shifting east as a
strong Pacific northwest trough tracks into the northern Great
Plains. A mid-level low over the Ohio Valley may spread some
clouds northwest into the area on Friday, but any associated
precip should remain outside of the CWA.

A surface low with the Pacific wave will likely occlude across
northern Ontario on Saturday, with a trailing cold front edging
eastward across the CWA late Saturday afternoon into Sunday.
Precip chances do not look overly high along the front with a mid-
level saddle point in the area and blocked Gulf of Mexico moisture
return by the Ohio Valley low. Seasonably cool conditions will
likely follow early next week, with an increased risk of dangerous
swim conditions behind the weekend cold front.



For the 12Z TAFs...

High pressure will result in VFR conditions with passing cirrus
through the period. VRB winds at TAF issuance will become a steady
east wind 10 knots or less late morning through Thursday.





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