Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/01/22

Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 513 PM CST Mon Feb 28 2022

.SHORT TERM...
Issued at 242 PM CST Mon Feb 28 2022

Through Wednesday night...

Gusty and mild southwest winds have set up across the area this
afternoon in response to the approach of a clipper system moving
eastward across the Upper Midwest. The boundary layer has become
well mixed (mixing heights up to 2500 feet AGL per an AMDAR
sounding out of MDW) in the warm sector this afternoon, and this
has supported warmer and breezy than expected conditions this
afternoon. Wind speeds will ease and lose their gustiness with
sunset this evening. Temperatures overnight should remain largely
above freezing across most of the area under partly cloudy skies.

The clipper system moving across the Upper Midwest this afternoon
is expected to drop a cold front southward down Lake Michigan
Tuesday morning, then into far northern IL by early Tuesday
afternoon. Temperatures ahead of this approaching boundary will
again be quite mild Tuesday with westerly winds. However, with the
passage of the cold front winds will turn northeasterly and
temperature will drop through the afternoon as much cooler air
shifts in off the lake. Areas well inland and south of I-80 will
be the warmest on Tuesday, with highs one again in the 50s under
partly sunny skies. Farther northeast towards Lake Michgian early
day highs in the low to mid 40s are anticipated, with readings
dropping into the upper 30s by late afternoon. A deck of lower
clouds may also shift in off the lake over portions of
northeastern IL late in the day and into the evening.

Conditions look to quickly improve (at least temporarily) across
the area on Wednesday as the next upper level impulse drives
another weak surface wave of low pressure eastward across WI.
Forecast guidance is in good agreement now in this resulting in
the Tuesday`s cold front shifting back north over the area as a
warm front for Wednesday. With winds expected to turn west-
southwestward once again, temperatures should warm into the 50s
across the entire area (could even have some 60 degree readings
south of I-80). Unfortunately, however, this warm-up will be short
lived as yet another cold frontal passage is expected by early
Wednesday evening. Breezy northeasterly winds and cooling
temperatures will again set up following this cold front for
Wednesday night.

Precipitation chances on Wednesday into Wednesday night will be
low, but not zero. The best potential for any light rain looks to
be north of the area in WI, but we certainly cannot rule out a
brief sprinkle or light rain shower making it into far northern
parts of IL during the day as the mid-level impulse shifts over
southern WI. At the present time we continue to leave the chances
for rain out of the forecast.

KJB

&&

.LONG TERM...
Issued at 319 PM CST Mon Feb 28 2022

Thursday through Monday...

The main weather story during the extend period continues to be
the expected shift towards more active weather pattern across
region next weekend, following a temporary shift to colder
weather on Thursday.

A large area of surface high pressure will build east-
southeastward out of the Prairie Providences of Canada, into the
Great Lakes Wednesday night into Thursday. East-northeasterly
winds in advance of this surface high will keep conditions rather
chilly across the area on Thursday, with highs only in the 30s,
under mainly cloudy skies. We will have to watch for the
possibility for a period of light snow late Thursday into
Thursday evening as warm air advection begins to ramp up over the
area in advance of low pressure taking shape over the central High
Plains. We currently continue to advertise a dry forecast for
this period, but I would not be surprised if we need to add a
chance for some light snow with later forecast updates.

Temperatures should begin to moderate some on Friday as warm air
advection continues overhead in advance of our next storm system
taking shape over the Plains. Unfortunately, easterly winds off
the lake will keep conditions cool over northeastern IL Friday.
This developing storm system over the Plains will be our primary
weather maker going into weekend.

Model and ensemble forecast guidance all support the idea of a
decent storm system shifting northeastward into the westerly
Great Lakes region late Saturday into Saturday night as a potent
mid-level impulse ejects out of the long wave trough setting up
over the western CONUS. While timing and track uncertainties
continue with this system, there is strong support that this
system will track to the northwest of the area late Saturday,
placing the forecast area in the warm sector.

The chances for showers will begin to increase across the area as
early as Friday night as warm moisture advection begins to
overtop a sharping warm frontal boundary setting up over central
IL. This warm front will shift northward into the area sometime
during the the day Saturday, with mild and breezy conditions
setting up to its south. Our best potential for more substantial
showers and thunderstorms with this system looks to be late in the
day Saturday and into Saturday evening as the systems cold front
approaches the area. Our chances of showers and storms will then
likely wane at some point late Saturday night following the cold
frontal passage. Depending on the actual evolution and timing of
this storm system, we could have some stronger storms nearby with
the cold frontal passage Saturday evening. This will have to be
monitored as we get closer to the event.

The active weather pattern looks to continue late Sunday into
Monday as a potential second impulse ejects out of the western
CONUS trough and shifts across the central CONUS. This may result
in yet another period of decent precipitation in our area
sometime late Sunday into Monday, but confidence on timing and
track of this second wave is rather low at this timescale.

KJB

&&

.AVIATION...
For the 00Z TAFs...

Breezy southwest winds will continue abating over the coming hours
and give way to speeds from 5 to 8 kt overnight. Broken VFR cloud
cover based near 25kft will spread over the terminals overnight.
Tomorrow, initially southwest winds will become northeasterly in
the wake of a cold front coming off Lake Michigan. Opted to
maintain the inherited timing of the wind shift af 18Z at the
Chicago terminals, and have introduced a timing of 21Z at DPA. At
RFD, winds should remain weak through most of the day but
gradually become northeasterly by mid-afternoon. At least
scattered MVFR clouds may attempt to work off Lake Michigan toward
the end of the TAF period, with perhaps a better chance after
about 03Z. For now, will maintain the inherited SCT020 at 18Z and
will reevaluate with the 00Z guidance for the 03Z AMD and eventual
06Z TAF package.

Borchardt

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...IL nearshore waters until 6 PM Monday.

&&

$$

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