Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 122328

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
528 PM CST Mon Feb 12 2018

215 PM CST

Through Tomorrow...

Quiet weather expected for the short term forecast period.

High pressure is building across the Upper Mississippi Valley and
will build east across the Great lakes region overnight tonight.
Generally light nnely winds will shirt to sely overnight. The main
issue of note will be increasing mid-level cloudiness overnight,
which will help limit radiational cooling over the fresh snow
pack. So, even with light winds and a dry air mass at the lower
levels, only expect that temperatures will drop into the single
digits overnight tonight. Through the day tomorrow, low level
flow will continue to shift to more southerly through the day as
low pressure develops over the western plains. Increasing low
level warm advection should allow temperatures to rebound back to
the lower 30s.  No precipitation is expected through tomorrow.


223 PM CST

Tuesday night through Monday...

Dry conditions expected at the start of the period, as WAA
continues across much of the region. This warming trend into the
middle part of the week will bring warmer temps to the area,
however, still not overly confident with high temps with current
snow pack in place and possible cloud cover. Nonetheless, above
normal temps appear likely across the CWA, especially south of
I-80. Confidence lowers going into Thursday with the arrival of a
front from the north and developing low pressure to the
south/southwest. These temp trends will need to be monitored as
its quite possible temps could be lower Wednesday into Thursday.
This could be problematic as precip chances increase late
Wednesday into Wednesday evening, and then again Thursday morning.
Thermal profiles Thursday morning would support a mix of precip
types, and if temps are around freezing, freezing rain would be
something to monitor for especially along/north of I-88. However,
guidance varying with pattern and precip chances during this time.
Will also keep an eye on rainfall amounts during this period,
especially during the day Thursday. This would be concerning given
the current snowpack in place. As this system progresses through
the region Thursday night into Friday, it is appearing that colder
air will filter in. This would support a transition back towards
a wintry mix/snow, before this system and precip depart Friday.
Dry and colder weather return by the weekend, before warmth
returns on Sunday. Model guidance varying significantly during
this time frame, but most showing an active weather pattern that
would support multiple periods of precip into early next week.
Whether that would be liquid or frozen is still unknown at this
time, but will be another period to keep a close eye on.



For the 00Z TAFs...

VFR conditions will prevail through the period. Surprisingly, a
lake breeze formed Monday afternoon and caused winds to flip more
easterly and a bit a stronger. Despite a favorable wind direction
for a lake breeze Tuesday, thinking the OVC conditions should
prevent one from forming.

- Izzi


223 PM CST

High pressure expected to move across the Great Lakes region
tonight, with winds diminishing and likely becoming variable
across much of the lake. This high does depart to the east early
on Tuesday, and will see winds quickly turn to the south, while
speeds increase. This steady increase in winds will result in
speeds up to 30 kt, especially across the north half. At this
time, speeds should generally stay confined to 30 kt, but it is
still quite possible for a period of gales late Tuesday into
Tuesday evening. Will keep winds to 30 kt, but will also make
mention of occasional gales, mainly over the north half. This
similar pattern of southerly winds will likely continue into the
middle part of the week.






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