Downers Grove, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

980
FXUS63 KLOT 130501
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1101 PM CST Tue Nov 12 2024

.KEY MESSAGES...

- Rain will develop late Wednesday afternoon, continue Wednesday
  night with linger showers Thursday morning.

- Temperatures will be near to above average through early next
  week.

- A pattern toward cooler and wetter conditions may materialize
  toward the end of the month.

&&

.DISCUSSION...
Issued at 145 PM CST Tue Nov 12 2024

Through Wednesday night:

The cloud cover is slowly scattering out across northern IL this
afternoon and this trend will continue into early this evening,
though still some uncertainty as to how fast the cloud cover
across east central IL, south of I-80, will scatter out.
Assuming the clouds do dissipate, generally clear skies are
expected this evening and then increasing high clouds will
spread across the area tonight into Wednesday. Low temps tonight
will generally be in the lower/mid 30s, but warmer in Chicago
and perhaps along the IL shore with southeasterly winds.

The next system will arrive Wednesday evening with low pressure
moving across the area Wednesday night into Thursday morning.
Moisture surges north ahead of this system Wednesday afternoon
into Wednesday evening with precipitable water values just over
one inch. This may translate into a narrow axis of heavier rain,
especially east of I-55. Model QPF amounts vary but WPC QPF
amounts are generally in the quarter to half inch range and this
seems reasonable for now. With the surface low expected to be
overhead early Thursday morning, there may be some fog issues
but visibilities may be dependent on any continuing rain. But
if the precip were to end, or diminish to a drizzle, fog will
need to be monitored with later forecasts but for now, did not
include any fog mention.

Ahead of the rain, southeast winds may gust into the 20-25 mph
range on Wednesday as highs reach the lower/mid 50s for most
areas. Perhaps a few upper 50s if more sunshine breaks through
the clouds. Temps will be generally steady in the upper 40s/
lower 50s Wednesday night. cms

Thursday through Tuesday:

Low clouds and lingering showers will define Thursday as the low
pressure system meanders away. Highs will be limited to the low to
mid 50s, which when combined with breezy northwest winds, will
complete a somewhat chilly day. Thursday night, clouds will be slow
to clear and keep temperatures in the upper 30s to lower 40s in
spite of the arrival of a pocket of relatively cool low-level air
characterized by 850mb temperatures between +1 to +2C. With that
said, marginal instability over Lake Michigan and only gradually
lowering inversion heights (by virtue of the back edge of the upper-
level trough axis taking time to move east of our area) may allow
for a few lake effect rain showers in northwestern Indiana overnight.

Friday into the weekend, a deep trough is expected to dig into the
southwestern United States causing expansive ridging to develop over
the Great Lakes. As a result, temperatures will gradually inch
upward with each day, with highs nearing the 60 degree mark by
Sunday. With time, the upper-level trough is expected evolve
eastward, though exactly how and when remains a source of varianace
among ensemble model guidance owing to different phasing
opportunities amongst a myriad of embedded upper-level shortwaves.
It will be interesting to see if and how the forthcoming tropical
cyclone in the Caribbean influences the overarching pattern toward
the end of the month, given the dominant upper-level jet stream and
embedded shortwaves will be close by. For what it is worth, ensemble
model guidance is steadfast in advertising a pattern shift toward
cooler, and perhaps "wetter," conditions across the Great Lakes
toward the end of the month, consistent with the forecast for the
North Atlantic Oscillation (NAO) to trend negative.

Borchardt

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1101 PM CST Tue Nov 12 2024

Aviation Forecast Concerns for the 06Z TAFs:

- Breezy southeast winds with gusts around 20 kt Wednesday.

- Rain develops by early evening, with deterioration of cig/vis
  into IFR and possibly LIFR Wednesday night.

High pressure centered northeast of the Great Lakes and low
pressure moving from the Plains into IL will maintain southeast
winds across the terminals through the period. Winds will
become breezy with gusts around 20 kt during the day Wednesday
and possibly briefly higher early Wednesday evening before
easing. The track of the low looks to be near/just south of the
terminals later Wednesday night, lending lower confidence in
wind directions (though speed should be decreasing) late in the
forecast period.

VFR high clouds will increase in coverage and thicken overnight
into Wednesday, with clouds lowering more quickly toward evening
as rain develops from the south/southwest. Rain looks to arrive
across the terminals in the 00-02Z time frame, with model
guidance in good agreement in depicting a rapid deterioration to
IFR by mid-late evening and potentially a period of LIFR after
midnight.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 9 PM CST Wednesday for Winthrop
     Harbor to Wilmette Harbor IL.

     Small Craft Advisory until noon CST Wednesday for Wilmette
     Harbor to Calumet Harbor IL-Calumet Harbor to Gary IN.

&&

$$

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