Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 11/30/21

Area Forecast Discussion

National Weather Service Chicago/Romeoville, IL

 552 PM CST Mon Nov 29 2021

.SHORT TERM...
Issued at 212 PM CST Mon Nov 29 2021

Through Tuesday night...

Quick-moving area of low pressure across NW Wisconsin has pushed a
warm front east of the Mississippi River where temperatures have
risen into the low to mid 50s (reminiscent of the situation a few
days ago). Temperatures across the rest of our area have warmed
into the lower 40s, but with dewpoints in the teens and 20s, the
wet bulb freezing line is near I-90 at this hour. Mping reports
and returns from TORD suggest there`s light snow falling out of a
4-5 kft cloud deck across NE Illinois. Recent AMDAR data also
suggest that lapse rates in the 800-600 mb layer have indeed
steepened up a bit, and brief convective instability is indicated
through this afternoon as the surface low swings into Wisconsin.

Indications point to the main rapid saturation occurring over the
lake and into lower Michigan into this evening, but continue to
suspect there may be a brief window through the rest of the
afternoon where the combination of intense lift, mid-level
instability, and dynamic cooling could support some additional snow
shower development near and NE of I-90. Given how warm we got
today, don`t envision accumulations or impacts with road temps
near 40.

The surface low will pass east of our longitude late this evening,
dragging a cold front through the region. The cold advection push
doesn`t look as intense as the past system, and currently not
seeing signs of overly gusty northwest winds. We turn somewhat
mild on Tuesday with highs rising back into the mid and upper 40s
under what looks to be a decent amount of sunshine, but clouds
thicken up rapidly again late Tuesday night with the approach of
yet another disturbance embedded within the fast northwest flow
aloft. Guidance today indicates just enough moisture with this
next system to justify some low-grade PoPs towards sunrise
Wednesday south of I-80. Thermal profiles suggest perhaps some
snow to start, but warming low-levels should trend things quickly
over to a cold rain into Wednesday morning.

Carlaw

&&

.LONG TERM...
Issued at 231 PM CST Mon Nov 29 2021

Wednesday through Monday...

Overall flow will remain from the northwest in the long term, at
least through this weekend and into Monday. This will continue to
allow short-wave "clippers" to continue to move through our region,
bringing the chance for precipitation. One such wave is expected
Wednesday morning, bringing a chance for initial rain-snow mix,
switching over to rain as low-level southwesterly flow pushes our
wet bulb to above zero. Southwesterly winds will become gusty,
advecting in warmer air at the surface, and allowing our highs to
climb into the upper 40s/lower 50s on Wednesday. Continued southerly
flow Thursday will continue to create above normal temperatures,
with lows around 40, and highs in the mid to upper 50s.

Another clipper will be close to my forecast area Friday morning.
Present guidance keeps precipitation to our north, but a slight
shift in this system`s path will increase our chances for
precipitation. Winds are expected to turn northerly Thursday
overnight, allowing temperatures to drop back into the mid to upper
30s Friday morning, with highs in the lower 50s.

Winds will remain northerly through Saturday into Saturday night.
This will bring our temperatures into the more seasonal range of
upper 20s/lower 30s for lows, and around 40 for highs. Long range
models are attempting to bring a surface low over us sometime this
weekend, with main time of concern Sunday into Sunday night, but
exact track and timing of this surface system is still spread out
among the models. Winds are forecast to presently remain from the
north into Sunday morning, so lows in the mid to upper 20s are
forecast for Sunday morning, and highs in the upper 30s to near 40.
Temperatures are expected to remain cool on Monday.

BKL

&&

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

Light precipitation is falling over the Chicago terminals this
evening but most of it isn`t quite reaching the ground. However,
heavier radar returns upstream suggest that we could see a light
sprinkle or flurry in the vicinity of the Chicago terminals through
about 02Z. Following this chance, the remainder of the TAF period
will be dry.

Wind gusts of 20+ kt are also only expected through around 02Z
across the metro before winds die down to around 10 kts for the
remainder of the night as they continue to veer reaching WNW
overnight. Mid to high level cigs will be seen tonight with clear
skies by morning as an awfully dry air mass pushes in from the
northwest. Winds will ramp up again pretty quickly through
Tuesday morning but won`t be quite as strong as they were today
gusting to around 16 kts through the afternoon and dropping to under
10 kts shortly after sunset.

Doom

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...Winthrop Harbor to Gary IN until 3 AM
     Tuesday.

     Small Craft Advisory...Gary to Michigan City IN until 3 PM
     Tuesday.

&&

$$

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