Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 242329

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
629 PM CDT Tue Apr 24 2018

200 PM CDT

Through Wednesday...

Low pressure across the Ohio and Tennessee valleys will finally
pull away from the region tonight. Lower clouds and maybe an
isolated shower will found along and east of I-55. On the heels
of this departing low, a cold front will move through tonight
ahead of a northern stream shortwave that is presently shifting
through the upper Midwest and upper Great Lakes. High pressure in
wake of this wave will enable gusty northeast winds to usher in a
cooler airmass beginning late this evening and begin our modest
temperature roller coaster ride that will continue for a few days.

Therefore, after some warm or at least seasonably warm days,
temperatures will take a dip on Wednesday following the passage of
the cold front. Brisk northeast winds will hold readings some 10
degrees colder in spots, with lower 60s south and west, and
readings in the 50s as you head closer to the lake. The warm April
sun should help to make it feel a bit warmer.



230 PM CDT

Wednesday night through Tuesday...

Overview...Looking at a pretty quiet extended with an early taste of
summer possible early next week.

High pressure will dominate the pattern Wednesday night through
Thursday evening. Seasonal temps and dry conditions are expected. A
lake breeze is possible Thursday afternoon, possibly leading to
cooler temps along the lake.

An upper level wave and cold front move across the region Thursday
night/Friday. Could see a ribbon of rain shift southeast across
the forecast area. Winds become northerly behind the front and
cooler air will lead to highs in the 50s to around 60 Friday.
Highs will be around 50 along the lake.

A large ridge builds over the CONUS over the weekend, and looking at
above normal temperatures early next week. 70s and maybe even 80s
are possible. High temps Monday and Tuesday could be warmer than
currently forecast, but I`d rather stick with the blend`s high temps
this far out. Guidance hints that clouds and perhaps showers and
storms could limit temps Tuesday.



For the 00Z TAFs...

Main aviation concerns are development of gusty north winds late
this evening/overnight as a cold front moves through the area, and
low probability of some brief MVFR cigs immediately behind the

Surface low pressure continues to track east across the Carolinas
early this evening, with a baggy cyclonic pressure field lingering
back across the Midwest. To the northwest, a cold front was
propagating southeastward, and will move across the terminals late
this evening/around midnight. Modest northeast winds and VFR
conditions can be expected early this evening, eventually turning
north behind the front and gusting above 20kts during the
overnight and early morning hours of Wednesday. Forecast sounding
profiles from various guidance suggest a brief period of MVFR cigs
is possible for a couple of hour behind the front, though current
surface obs and satellite imagery depict no low clouds upstream,
lending low confidence to MVFR conditions of any significant
duration. Will have to watch things especially over Lake Michigan
for potential development of lower clouds, with GYY the most at
risk due to proximity and direction of fetch behind the front
later tonight.

Clouds clear out Wednesday morning, with gusty north winds
gradually easing into the afternoon. Lake breeze will likely form
and turn winds a bit more northeast at ORD/MDW by mid/late



230 PM CDT

A cold front will move down Lake Michigan this evening and overnight
with northerly flow strengthening in its wake. Wind gusts are
expected to peak around 30 kt late this evening and overnight, then
should very gradually diminish through the day Wednesday as a ridge
of high pressure spreads across the region. A small craft advisory
remains for the Illinois and Indiana nearshore waters for this
evening through Wednesday evening. Winds flip to southwest behind
the ridge axis on Thursday and ahead of another approaching cold
front. This next front is expected to sweep across the Lake Thursday
night possibly bringing another period of north winds gusting to
around 30 kt.



LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...10 PM Tuesday to
     10 PM Wednesday.

     Small Craft Advisory...LMZ743-LMZ744-LMZ745...1 AM Wednesday to
     1 AM Thursday.




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