Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 150829

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
329 AM CDT Sun Apr 15 2018

318 AM CDT

Through tonight...

Low pressure over Central Indiana will reach the Eastern Great Lakes
around midnight tonight. Widespread showers continue this morning.
Areas north of I-88, especially along the IL/WI state line, will see
a wintry mix, and the mix will likely contain periods of freezing
rain with up to an tenth of an inch of ice possible. The freezing
rain will likely cause difficult if not dangerous travel conditions
this morning.

The column will slowly cool allowing rain to become snow early this
afternoon in the Winter Weather Advisory area.  I agree with the
previous shift that while light snow will continue tonight, the main
hazard is freezing rain, which will end early this afternoon with
the Winter Weather Advisory.

Areas along and east of the I-55 corridor may see dry periods this
afternoon, but near term models continue to show scattered showers
will form this afternoon. As such, I kept a chance of precip going
through the afternoon. The rain/snow line will slowly shift
southeast through this evening, and brief periods of sleet are
possible during the transition. Light snow continues overnight as
the upper level low rotates over the region.

Up to an inch of snow is possible north of a Polo to Woodstock, IL
line. All other areas should see less than a half inch of snow
through Monday morning.



318 AM CDT

Monday through Saturday...

Overview...Snow ends Monday, but another system may bring a wintry
mix to the region Tuesday night and mid week.  Temps warm to near
normal late this week.

Vorticity streamers on the upper level trough`s backside rotate
through Monday morning leading to more light snow showers. Little to
no accumulation is expected.

High pressure builds overhead Monday night/Tuesday allowing temps to
rise into the 40s-50s.  The next system moves into Southeast Iowa
Wednesday morning. Warm air aloft will allow snowflakes to fully
melt, but surface temps below freezing along the IL/WI state line
will be favorable for freezing rain. Surface temps warm Wednesday
morning as the warm sector shifts north turning all precip to rain.
Gusty southwest winds accompany max temps in the upper 40s along the
IL/WI state line to low 60s south of I-80.

Another cold air push follows the low Wednesday night, and rain will
either mix or completely turn over to snow. High pressure late this
week brings another stretch of drier and near normal temperature
days. A low passes over the Southern Mississippi Valley over the
weekend, and its precip shield may extend over the forecast area.



For the 06Z TAFs...

Forecast period will see continued precip chances across the
terminals with reduced vis, low ceilings, and varying winds.
System moving across the region providing steady rain across the
terminals early this morning, with this trend likely to continue
for much of the morning. In the near term, expect rain for the
terminals. However, RFD could occasionally see a mix of rain or
sleet over the next several hours. Think rain would be the more
prevailing precip type, but will continue to monitor trends.
Steadier precip exits closer to midday, but think more showery
development will take its place this afternoon into the evening.
All rain for most of the day, but this will transition over to all
snow by the late afternoon and evening. Do have lower confidence
with snow trends later this evening, but will monitor for possible
lower vis than currently forecast. IFR ceilings are likely for
much of the period and do think periods of LIFR ceilings are
possible, but confidence is lower with these ceilings. Stronger
northeast winds will continue this morning, before a diminishing
trend occurs later this morning. A shift over to the northwest
will then occur later today.



328 AM CDT

Strong winds will persist across much of the lake today into
tonight, as the lake remains in between strong low pressure to the
southeast and strong high pressure over southern Canada. While
the strongest winds will be across the northern portions of the
lake, gales are still anticipated over much of the lake this
morning, including the Illinois nearshore. Winds do diminish over
the southern portions of the lake through midday, but remain
elevated over the north half. Have maintained strongest winds of
gales to 45 kt over the northern parts of the lake, however,
continue to monitor the possibility for occasional storm force
winds later this morning into early afternoon. Have not issued a
storm warning for this location as expect these higher winds to be
sporadic, and should not last too long in anyone location. Did
include occasional wording in the open waters forecast though. In
this location, do also expect gales to last longer into tonight,
and have extended the gale warning. Will need to monitor later
trends and guidance, as it`s possible that these gales could last
slightly longer.



IL...Lakeshore Flood Warning...ILZ006-ILZ014 until 10 AM Sunday.

     Winter Weather Advisory...ILZ003-ILZ004-ILZ005-ILZ006 until 1 PM

LM...Gale Warning...LMZ740-LMZ741-LMZ742-LMZ777-LMZ779 until 10 AM

     Small Craft Advisory...IN nearshore waters until 5 PM Sunday.




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