Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 230809

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
309 AM CDT Mon Apr 23 2018

306 AM CDT

Through tonight...

Low-impact weather is expected through tonight as dry low-level
easterly flow continues while an upper-level low near the MS/OH
River confluence meanders along the KY/TN line. Overall conditions
today should be rather similar to what was observed on Sunday for
most the area, with a bit more mid to upper-level cloud cover
expected today.

The ongoing rain across southern IL will begin to dissipate as it
encounters the very dry low-levels across the north half of IL
today. Top-down saturation may allow for some isolated to scattered
showers to gradually spread into the southern CWA this afternoon and
the remainder of the CWA through the night. Guidance appears to be a
bit aggressive with the northward extent of this precip in terms of
coverage given the antecedent dry air mass. Overall expectation is
for isolated, low-QPF showers, with much of the area remaining dry
through the period.



306 AM CDT

Tuesday through Sunday...

Tuesday through Wednesday night: The approach of mid-level troughing
over the Upper MS River Valley should allow for a slightly better
chance of low-QPF showers across the CWA on Tuesday when compared to
tonight. Still, coverage should be isolated, with only a few being a
heavy enough to wet the ground. Any showers will shift east from the
CWA during the night. A dry, cool, and somewhat breezy day is
expected for Wednesday, with just diurnal cumulus and some passing
high clouds.

Thursday through Friday: Upper-troughing originating from western
Canada will shift SE across the Upper MS River Valley on Thursday
and the western Great Lakes Thursday night into Friday. An
associated band of scattered showers is expected to cross the CWA
late Thursday night through Friday afternoon.

Saturday and Sunday: Cool but dry conditions will prevail on
Saturday under NW flow behind the departing trough. An approaching
ridge will cross the region on Sunday, bringing a seasonable and
mostly sunny late April day to the area.



For the 06Z TAFs...

Ridge of high pressure will remain over the Great Lakes while an
upper low very slowly meanders northward along the mid Mississippi
Valley. Persistent northeast wind will be in place through the TAF
period with a slight diurnal uptick above 10 kt. VFR conditions
and dry weather will prevail under the influence of the high, but
late Monday evening into the overnight hours, moisture wrapping
around the upper low will reach northwest Indiana and possibly
northeast Illinois reducing ceilings to MVFR and resulting in a
few scattered showers and sprinkles. GYY has the best chance for
any precip, but only enough confidence to include a prob30 at this
time. Will include only a VCSH at the remaining Chicago-land



306 AM CDT

Ridge of high pressure will remain over the central and northern
portions of Lake Michigan over the next couple days while a moderate
to fresh northeasterly breeze will be in place across the south half
of the lake. A cold front will move down the lake Tuesday night with
north wind gusts increasing to around 30 kt. Moderate north flow
will continue much of the day Wednesday, but should very gradually
diminish as ridge of high pressure builds across the region. Winds
swing around to the south/southwest on Thursday behind the ridge
axis, but another cold front will sweep down the lake Thursday night
bringing another period of northerly winds gusting to around 30 kt.






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