211
FXUS63 KLOT 141737
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
1237 PM CDT Sat Jun 14 2025

.KEY MESSAGES...

- Chance for showers this morning, mainly southeast of a
  Livingston County to Jasper County line

- Temperatures will increase this weekend and into next week,
  accompanied by increasing shower/storm chances by midweek.

- Severe weather is possible next week, particularly Wednesday,
  with multiple rounds of thunderstorms possible Monday through
  Wednesday night.

&&

.DISCUSSION...
Issued at 302 AM CDT Sat Jun 14 2025

Through Sunday:

KLOT radar is showing diminishing shower coverage over the
southeastern portions of the forecast area. These showers are
situated along and just north of a quasi-stationary boundary
from St. Louis, MO to Lafayette, IN. This boundary is associated
with an upper level low sitting over eastern
Missouri/southwestern Illinois. Over the next 6 to 12 hours,
this low is expected to weaken as it slowly moves east over
southern Illinois. Its gradual movement will help nudge the
surface boundary southeast of the forecast area through the
morning. Showers are expected to linger through the morning and
into the early afternoon mainly along and southeast of a
Livingston County to Jasper County line. Weak forcing should
help keep rain rates low, though with over two inches of
precipitable water there remains a chance for a downpour to
focus over an area that received rainfall last night which
result in ponding in flood prone areas. Lastly, model soundings
do show an a sliver of instability late this morning and into
the afternoon. However, those soundings are fairly capped and
not expected to break that cap until the showers move southeast
of the area. Perhaps an isolated thunderstorm or two develops,
but the better instability will be to the south along the
boundary as it slinks away from the forecast area through the
day.

An upper level high will strengthen over New Mexico and build a
ridge into the Plains today. Drier air and increasing
subsidence moving into the forecast area ahead of the ridge is
expected to reduce cloud cover this afternoon, at least to the
west. Temperature are expected to reach he lower 80s for areas
west of the Fox Valley which should receive more sunshine.
However, as cloud cover is expected to linger for much of the
day closer to the lake and over northwestern Indiana, that (and
northeast winds over the lake) should help cap high temperatures
for those areas in the mid to upper 70s. Cloud cover will
continue to erode tonight as dry conditions prevail and low
temperatures in the upper 50s/low 60s are expected.

As a weak upper level pattern remains, most of Sunday should
stay dry. Clearer skies should allow for more of the forecast
area to warm up solidly into the 80s, though northeast winds off
of the lake will help keep the lake shoreline in the 70s.
Models keep suggesting a very weak upper level short wave that
develops and moves down the ridge from southeastern Minnesota to
southern Wisconsin. Combine that with diurnal heating and there
is a slight (less than 25 percent) chance for some showers and
thunderstorms on Sunday afternoon in northwest Illinois and
along the Wisconsin stateline. There is better confidence for
the showers and storms to be northwest of the Rockford Metro
area, but whether or not it materializes will depend on the
movement of that wave and how close to the forecast area it gets
before the sunsets and a less favorable time of day for storms.

DK

Sunday Night through Friday:

Guidance remains in good agreement in depicting a more zonal
flow pattern in the mid-upper levels to start next week. Surface
high pressure stretching from the Great Lakes through New
England drifts slowly to the east Sunday night into Monday,
while warm, moist southerly return flow develops off of the
western Gulf into the Plains and upper Midwest/Mississippi
Valley. Models depict several low-amplitude short wave
disturbances tracking eastward across the region along the
southern periphery of stronger jet winds, which should modulate
diurnal thunderstorm initiation across the upper Midwest and
development of a few MCSs, which could affect our forecast area.
Various models show quite a bit of differences in details with
these low-amplitude waves, not surprisingly, leading to fairly
low confidence in exact timing and placement of them and any
organized convective complexes they produce.

Global ensembles continue to indicate a more amplified mid-
level short wave tracking across the central and northern
Rockies and onto the Plains late Tuesday and into the Midwest
Wednesday/Wednesday night. While some differences remain with
the timing and strength of this feature, the general trends
support an area of surface low pressure lifting northeast across
the upper Midwest Wednesday with attendant synoptic increases
in low-level warm sector theta-E, instability and vertical wind
profiles. This pattern appears supportive of heightened severe
thunderstorm potential within the region on Wednesday, which
will continue to be monitored for a possible severe weather
threat in or close to the WFO LOT forecast area.

Ridging in the wake of the more amplified mid-week system may
ease the periodic shower and thunderstorm threat for at least a
portion of the latter half of the week, though there is some
indication that the main upper ridge axis will set up to our
west keeping us along the southern periphery of additional
shower/thunderstorm threats across the upper Midwest.

Temperatures are forecast to warm into the mid-upper 80s early
next week, with 90 not out of reach especially Tuesday and
Wednesday. This will be dependent on thunderstorm trends and
affects of any outflow boundaries, however, lending somewhat
lower confidence to current forecast highs. Humidity levels will
be on the rise through mid-week as well.

Ratzer

&&

.AVIATION /18Z TAFS THROUGH 00Z MONDAY/...
Issued at 1237 PM CDT Sat Jun 14 2025

Only forecast concern is mvfr cigs early this afternoon. Mvfr
cigs across the Chicago terminals and areas south of the
terminals will lift to low vfr over the next few hours and also
begin to scatter out, dissipating this evening. Increasing high
level clouds are expected tonight into Sunday.

Northeast winds around 10kt will diminish this evening and are
expected to become light and variable across most of the area
tonight, becoming northeast again Sunday morning.

There is a small chance for a few showers across northwest IL
and RFD Sunday morning. Confidence is too low to include any
mention with this forecast. cms

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

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