Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 010139

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
839 PM CDT WED AUG 31 2016

839 PM CDT

No big changes planned to the grids this evening, though do plan
to nudge pops up just a bit and go with scattered showers near the
lake over NE IL Thursday morning. While certainly not the most
explosive lake effect set-up I`ve ever seen, lake induced
equilibrium levels climbing to around 8000ft agl along with
several hundred j/kg of lake induced CAPE should be enough to kick
off scattered showers, particularly in the morning when a land
breeze convergence zone is likely to develop and focus forcing.
A few showers could linger into the early afternoon near the lake,
but chances look to dwindle pretty quickly during the afternoon
with loss of convergence. Updated grids/derived products coming



207 PM CDT

Through Thursday...

Northerly winds today in the wake of this mornings cold frontal
passage, have resulted in a transition to a cooler and drier air
mass from north to south. Temperatures this afternoon will likely
top out in the mid to upper 70s north and near 80 south. This cool
weather will be reinforced for Thursday as another shot of even
cooler air shifts southward over the area as surface high pressure
builds into Ontario and the Upper Great Lakes. As this cooler air
mass shifts over the warm Lake Michigan waters, this will likely
result in some lake effect cloud cover on Thursday. There is also
a chance for some isolated sprinkles or light lake effect rain
showers Thursday, especially into northeastern Illinois. However,
it does not look like a great threat for measurable precipitation,
though as inversion heights will be limited due to a thermal
inversion expected just above 800 MB. Still a few light showers
will be possible. Otherwise, expect temperatures to be cooler in
the low to mid 70s in most areas.



303 PM CDT

Thursday night through Wednesday...

The longer term forecast period will start out with a
continuation of quiet weather as high pressure slowly spreads to
the upper Great Lakes with a ridge axis extending southwest
through the middle and upper Mississippi Valley. The quiet weather
will persist through the weekend, with temperatures starting out
below seasonal normal levels, with lows in the lower to middle
50s. High temps will also be below normal with highs in the middle
to upper 70s through Saturday. The temperature trend should be for
gradual warming into the middle of next week as the high pressure
slowly moves to the east and low pressure developing over the
western plains lifts into the Dakotas with a trailing cold front
extending southwest into the central plains. With a warm
advective pattern under swly flow developing at the sfc and broad
ridging aloft, temperatures should reach into the lower 80s by
Sunday and the mid 80s by midweek. As for precipitation chances,
the dry conditions should persist through the weekend and into
early next week. The next significant chance for pcpn will not be
until toward the end of the period, Monday night or Tuesday as the
low lifting through the nrn plains continues to lift northeast
toward Hudson Bay while dragging a cold front in it`s wake. the
front is not expected to reach the local area until midweek,
bringing increasing chances for showers and thunderstorms.


For the 00Z TAFs...

North to northeast winds will prevail through much of the forecast
period with winds diminishing over the next hour, but increasing
once again early Thursday morning. VFR conditions expected this
evening into the overnight hours but am still monitoring for MVFR
ceilings and scattered light showers to move off the lake early
Thursday morning. General time frame in the TAF seems reasonable,
but will need to monitor for the possibility of a slightly sooner
arrival, possibly in the 10-12z range. Any shower that passes over
the TAF sites Thursday morning will be brief and light.



303 PM CDT

Strong high pressure building over the northern plains and
into the upper Mississippi Valley, combined with a trough of low
pressure moving into the Ohio Valley has generated strengthening
northwest to north winds over Lake Michigan. With increasing cold
advection, expect that winds will reach up to 30 kt over some
portions of the lake tomorrow afternoon or evening. Waves over the
south end of the lake could, occasionally, as high as 10 ft. Brisk
winds and high waves should persist over the lake through Thursday
night. Conditions should settle down by Friday as high pressure
builds across the Great Lakes Friday, with mild conditions
continuing through the weekend.


IL...Beach Hazards Statement...ILZ006-ILZ014 UNTIL 10 PM Thursday.

IN...Beach Hazards Statement...INZ001-INZ002 UNTIL 10 PM Thursday.

LM...Small Craft Advisory...NEARSHORE WATERS
     UNTIL 10 PM Thursday.




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