Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KLOT 220755

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
155 AM CST Wed Nov 22 2017

123 AM CST

Through Thanksgiving Day...

Quiet conditions will be in place for the busy travel day and for
Thanksgiving Day.

It will indeed be a cold start to the day in wake of yesterday`s
front, though lake effect cloudiness across northwest Indiana is
doing its work as a natural blanket to keep things warmer in lee
of the lake. High pressure across the plains will shift into the
region today which allow for winds to slacken over what has been
several windy/breezy days. The high center will pass to our south,
so we will still maintain a lighter wind that will shift to
southwest through the day. In spite of warm advection kicking in
through the day, highs will struggle to get out of the 30s. Some
passing high clouds will give way to some thicker mid and high
clouds ahead of the next disturbance, this one currently across
Canadian prairies/northern plains. The wave will pass through
Wisconsin tonight, providing us just increased cloud cover and a
warmer night. Weak high pressure will fill in behind this weaker
system for Thanksgiving day, which will result in mostly sunny
conditions and temperatures in the lower to mid 40s, just a tad
below normal.



123 AM CST

Friday through Tuesday...

The only real chance for precipitation will be Friday night. The
up and down pattern continues as low pressure will again deepen
north of Lake Superior Friday in a similar fashion to what
occurred on Monday. With a sub 980 mb low, expect south/southwest
winds to increase quickly, and highs will be on par with or maybe
a tad higher than Monday`s highs which were in the low to mid 50s.
The pendulum will shift back down on Friday night with the cold
front providing a chance for some light rain. This cold air is
only a glancing blow, thus temps Saturday will be near normal in
the low to mid 40s. Expansive high pressure across the west will
shift in Saturday night into Sunday, resulting in a cold night and
cool day Sunday, though cloud cover will be minimal.

Longer range guidance, which has been all over the place for some
time here, is indicating a system will eject out of the west
early in the week. All indications are that this system will
impact areas to our north a bit more, with our region remaining on
its warmer and generally drier side, though it could bring some
light rain.



For the 06Z TAFs...

No significant aviation forecast concerns through Wednesday night.

Strong surface high pressure continues to build southeast across
the Plains overnight in the wake of Tuesday`s cold frontal
passage. Cold, dry low level air spreading in on northwest winds
has allowed skies to clear across the region, except for some VFR
3500-4500 foot stratocu along the lake and downwind into northwest
Indiana and Michigan. This too will shift off to the east
Wednesday morning as low level winds back more westerly. Winds,
still above 10 kts at times late Tuesday evening, will continue to
diminish and back to the southwest by Wednesday afternoon. Speeds
will come up a bit again Wednesday night. Warm air advection will
spread lowering VFR cloud cover back across the terminals late in
the day and Wednesday night.




155 am...A large area of high pressure over the plains will move
east to the Ohio Valley tonight and then drift east across the mid
Atlantic on Friday. Strong low pressure will move across Ontario
Friday and Friday night with a tight pressure gradient developing
over the lakes region. Southwesterly gales are likely over Lake
Michigan Friday. Speeds may diminish a bit Friday night as a cold
front moves across the lake by Saturday morning. A shorter period
of gales is possible Saturday as colder air spreads across the
lake but confidence is lower for gales behind the front. A ridge
of high pressure is expected to cross the lake Sunday. cms


LM...Small Craft Advisory...IN nearshore waters until 9 AM Wednesday.




WWW.YOUTUBE.COM/NWSCHICAGO is the U.S. government's official web portal to all federal, state and local government web resources and services.