Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 200602

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
102 AM CDT Tue Mar 20 2018

127 PM CDT

Through Tuesday...

Breezy east-northeasterly winds are expected to continue through
the period as low pressure tracks eastward well south of the area
and high pressure remains dominate over Ontario tonight into
Tuesday. This northeasterly flow will transport a colder airmass
over the area for Tuesday resulting in cooler high temperatures
area-wide. High temperatures Tuesday are expected to be in the
low to mid 40s well inland, but likely only in the mid to upper
30s closer to the lake under partly cloudy skies. Conditions will
feel even cooler than these values, however, as winds continue to
gust up to 25 to 30 mph during the day.



214 PM CDT

Tuesday night through Monday...

Overview...Temperatures look to be slightly cooler to near normal
through the extended.  I have uncertainty about how the Friday
night/Saturday system will evolve, but most if not all of the
forecast area should see precip.

Cooler than normal conditions continue Tuesday night with moderating
temperatures Thursday as an upper level ridge begins to push east.
Quiet and near normal temperatures continue Friday under a broad
high pressure ridge.

The next low forms over the Southern Plains Friday night, and the
low weakens as it passes over the Mid Mississippi Valley Saturday
night.  An upper level wave passes over the region while the low
passes to our south, bringing precip to the region.  Guidance
differs on how far northeast the precip shield will reach, and I`m
expecting mainly rain Saturday.  There could be a period of heavier
rain Saturday evening before the forcing and precip shift east.  The
ECMWF suggests precip may linger into Sunday morning, while the GFS
has the system falling about quicker.



For the 06Z TAFs...

The element of interest for the TAFs remains winds for today and
tonight. Northeast winds through daybreak will show occasional
gusts into the lower to mid 20s knots. A slight increase is
expected after daybreak with frequent gusts into the mid 20s and
sporadic into the upper 20s. Winds will ease very slowly tonight.

Confidence is high in wind speeds and gusts, while confidence in
wind direction is medium-high. There is likely to be some
direction fluctuation within the northeast quadrant of the
compass, and could back as far as 020 degrees at ORD and MDW at

While a few 1000-3000 ft clouds are possible today and tonight,
the flow off the lake will generally remain dry enough to prevent
low clouds.



101 AM CDT

Strong northeast flow will continue over the lake today with a
gradual weakening tonight. Gusts to around 30 kt will be frequent
across the south today, and occasional for central and northern
parts of the lake. Frequent wave action to near 10 ft with
occasional higher is forecast today in the Illinois and Indiana

With low pressure deepening off the Northeast U.S. shore on
Wednesday, the winds over the region will turn more due north and
remain somewhat elevated (15-20 kt gusts). This likely will
continue Small Craft Advisory waves, or at least near it, in the
Indiana and possibly the Illinois nearshore through the day
Wednesday. Ridging will then move over the lake during Wendesday
night-Friday bringing quieter conditions.

The next low is expected to move eastward into the Ohio River
Valley this weekend, bringing stiff east to northeast winds once



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




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