229
FXUS63 KLOT 080527
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1227 AM CDT Wed Apr 8 2026

.KEY MESSAGES...

- 20-30% chance for a period of wintry mix tonight, mainly north
  of I-80.

- Gusty south-southwest winds on Wednesday with gusts peaking
  around 30-40 mph.

- Mild with periods of showers and some storms Wednesday night
  into at least Friday, and again from later in the weekend into
  early next week.

&&

.DISCUSSION...
Issued at 223 PM CDT Tue Apr 7 2026

A surface high continues to drift across the Great Lakes this
afternoon resulting in mostly sunny skies and light easterly
winds. However, the sun is not helping temperatures much with
most areas sitting in the mid to upper 30s to around 40 and
those readings are not expected to improve much before sunset.

Heading into tonight, the subtle shortwave trough noted in
water vapor imagery over the WY, NE, and SD borders will pivot
into the area after midnight. Mid-level warm advection will
increase as the wave approaches and winds aloft turn
southwesterly which will also begin to advect the area of
showers in southern IA and MO into northern IL. With
temperatures expected to dip near to just below freezing
(28-32F) as the showers arrive, the dominant precipitation type
should be snow. Though, as temperatures warm overnight
(especially aloft) the snow should transition to rain but not
before a brief period of sleet tries to mix in. Despite decent
agreement in guidance, the marginal moisture profiles make the
coverage of any precipitation tonight low confidence
particularly with southward extent. Therefore, have opted to
maintain the slight to chance (20- 30%) POPs mainly focused
north of I-80 tonight with the main area of wintry mix favored
near the IL-WI line.

Precipitation tonight will taper by daybreak Wednesday
resulting in another dry day for us. In fact, with the
aforementioned warm advection temperatures on Wednesday will
rebound nicely into the mid to upper 60s areawide. Winds will
also be on the increase Wednesday as a surface low begins to
approach the northern Great Lakes. South- southwesterly Gusts
are currently forecast to peak around 30-40 mph Wednesday
afternoon, but if skies are able to clear out and deeper mixing
is achieved then locally higher gusts could be realized.

While we enjoy another mild spring day on Wednesday, an upper
low will be across the northern Plains towards the Great Lakes
with its associated surface low. Attached to the low will be a
cold front that will be stretching from WI to KS that will move
into northern IL and eventually northwest IN Wednesday night.
Initially some scattered showers (and perhaps even a couple of
thunderstorms) should be ongoing along the front, but as the
front moves into our area the drier air in place looks to cause
the showers to become more isolated with time. Thus rain chances
look to wane by Thursday morning. However, the front is
expected to stall somewhere in our area Thursday morning and
will serve as the breading ground for more showers and
thunderstorms Thursday afternoon/evening as a trailing shortwave
dives out of the northern Plains. While the stout southwest
winds should advect in some better moisture to help destabilize
the atmosphere Thursday afternoon, forecast soundings continue
to show CAPE profiles being rather meager. So suspect that there
will be some scattered thunderstorms Thursday afternoon and
evening, but the threat for severe weather looks low given the
weaker instability and modest wind shear around 30-35 kts.

The frontal boundary should begin to slowly meander southward
Thursday night into Friday with showers and embedded
thunderstorms expected to linger along the boundary as it does
so. In fact, with storm motions expected to be parallel to the
frontal boundary conditions do look favorable for training
convection which could result in localized threat for flash
flooding especially if storms overlap areas that saw heavy
rainfall this past weekend. Outside of the rain, temperatures
for Thursday look to be seasonably warm again with highs in the
60s to lower 70s (warmest south of the frontal boundary).
Though, Friday will be a bit cooler due to northeast winds so
highs will only be in the mid 50s to lower 60s inland with highs
in the 40s near the lake.

Looking into this weekend, guidance has been trending drier for
Saturday as the frontal boundary is now forecast to get shoved
into the Ohio River Valley as mid-level ridging slides overhead.
However, broad upper-level ridging is forecast to develop in
the western CONUS which will be sending several shortwaves at
the Great Lakes this weekend into the early part of next week.
Depending on how strong the ridge becomes Saturday will
determine if the leading shortwaves are able to be shunted into
WI or if they will make a pass over portions of northern IL
and/or northwest IN Saturday night and bring us more chances for
showers and thunderstorms. Given that this is low confidence
have opted to maintain the offered 20-40% POPs Saturday night
into Sunday for the northern half of the area, but suspect most
areas will be dry especially with southward extent. Regardless
on how Saturday night plays out, the aforementioned ridge is
forecast to drift east on Sunday which should allow a more of
the shortwaves (and any associated storm systems) to move into
the region particularly during the Sunday night and Monday
timeframe. Though, guidance does vary greatly on exactly when
this next system will arrive so there is a chance that Sunday
remains dry as well with rain not arriving until sometime Monday
morning. Due to the lower confidence in how this all shakes out
we recommend keeping an eye on the forecast going forward.

Yack

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1227 AM CDT Wed Apr 8 2026

Key Aviation Messages for the current TAF period:

- Light rain, and potentially some snow mixed in, moves over
  northern Illinois early this morning.

- Gusty southeast winds will switch to the southwest around
  midday. Max wind gusts this afternoon are expected to exceed
  30 knots.

- Better chances for rain overnight tomorrow night.

A band of precipitation has crossed the Mississippi and will
continue to move east through around 09Z. Surface temperatures
have remained above freezing out west, so for now the
expectation is for the dominant precip type to be rain. However,
those temperatures are only just above freezing. It would not
be surprising if some snow or even an ice pellet were to mixed
in. The good news is that surface temperatures are expected to
slowly warm through the night, which helps add confidence that
any frozen precip should be for a limited window and be fairly
non-impactful.

Winds remain out of the southeast and will become fairly gusty
after sunrise. By midday, winds are expected to turn to the
south and eventually southwest in the early afternoon. Gusts 25
to 30 knots can be expected through the day, but peak wind
gusts in excess of 30 knots can be expected in the afternoon.

As a surface low moves eastward over southern Canada tomorrow
night, it will send a front across the upper midwest and drive
another line of showers across the region. There is a non-zero
chance for thunder, but the probability was too low to include
in the TAF.

DK

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory from 7 AM this morning to 4 AM CDT
     Thursday for the IL nearshore waters.

     Small Craft Advisory from 7 AM this morning to 7 AM CDT
     Thursday for the IN nearshore waters.

&&

$$

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