Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 201805

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
Issued by National Weather Service Lincoln IL
1259 PM CDT Tue Mar 20 2018

328 AM CDT

Through tonight...

Generally quiet, but blustery, weather expected today.

Brisk northeasterly winds should continue through the day today as
low pressure moves through the Upper Ohio Valley while strong high
pressure remains parked over Ontario.  A complex series of
shortwaves over the Middle Mississippi and Upper Missouri Valleys
are spreading increasing and thickening cirrus over the region, but
will, otherwise, have little impact on local weather conditions.
With persistent flow off of Lake Michigan, some increasing lower
level cloudiness is expected across nern IL/nwrn IN through the day
as well as keeping temperatures 5 to 10 degrees below seasonal
normal levels today.  Highs closer to the lake should top out in the
middle to upper 30s, while only reaching the low to middle 40s well
inland.  Lows tonight should be in the middle to upper 20s under
mostly cloudy skies.


328 AM CDT

Wednesday through Monday...

Little change has been made to the going longer term forecast as
general trends remain consistent with previous forecasts.  The
latest longer range model runs continue to indicate a period of dry
weather into Friday night.  Temperatures should remain a bit below
normal through Wednesday, but then trend closer to seasonal normal
levels as the upper level pattern trends more progressive with upper
level ridging moving out of the Rockies and over the Central Plains.

The longer range models are beginning to come into better agreement
on handling the next system to impact weather over the local area,
with low pressure developing over the Central Plains Friday night
and then tracking through the Middle Mississippi Valley Saturday and
then continuing through the Ohio Valley Saturday night and Sunday.
There are still some timing and intensity differences among the
models, but the general track is coming into a little better
agreement with the low center moving through srn IL/IN.  Pcpn is
likely with the system across the entire CWA, with the main concern
being p-type.  Thermal profiles are looking marginal for snow and
much of the pcpn being rain or a rain/snow mix, though there may be
short periods of wet snow during the diurnal min temp hours.  By
Sunday, the ECMWF continues to trend slower with upper ridging
building across the region behind the exiting system, so there is
still some concern that some pcpn could linger into Sunday morning.
there should be a short dry period as the upper ridge quickly moves
across the area, but another wet period looks to be setting up for
Sunday night and into early next week shortwave energy lifts through
developing swly flow aloft ahead of a longwave trough deepening over
the Rockies.


For the 18Z TAFs...

VFR conditions are gernally forecast to continue across the northeast
IL airports through Wednesday. Gusty NE winds will prevail through
early evening with gusts of 22-28 kts. Also still concerned there
may be some MVFR stratocumulus cloud potential due to flow off Lake
Michigan this afternoon at ORD, MDW and GYY.

Northeast winds around 15 kts with gusts of 22-28 kts continues
through early evening due to 998 mb low pressure over the mid
Atlantic states.
Confidence is highest in the 030-040 degrees direction for today.
Late this afternoon into this evening, guidance is indicating slight
backing to 010 to 020 direction with NNE winds of 10-14 kts tonight
into Wednesday. Some guidance shows wind gusts of 15-20 kts on Wed

Broken to overcast mid-high clouds of 15-25k ft to prevail through
Wed, though guidance showing these clouds decreasing from the west
late Wed afternoon. The NE flow off the lake has developed patches
of 2-3k ft clouds and carried few-scattered stratocumulus clouds
through Wednesday. Can not rule out brief broken MVFR ceilings at
ORD, MDW and GYY this afternoon, but as winds veer more northerly
tonight, this will become less likely tonight and Wed. ILX


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...IN nearshore waters until 10 PM

     Small Craft Advisory...IL nearshore waters until 4 PM Wednesday.




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