Schererville, Indiana 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

956
FXUS63 KLOT 160023
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
723 PM CDT Fri Aug 15 2025

.KEY MESSAGES...

- Uncomfortable heat and humidity this weekend into early next
  week. Daily heat indices could top 100 degrees particularly
  near and south of I-80 Saturday through Monday.

- Periodic thunderstorm chances tonight through Tuesday, but
  many dry hours are likely too. The strongest storms will be
  capable of gusty winds and flash flooding.

- A cooler (seasonable temperatures), less humid, and mainly dry
  stretch appears likely from the middle of next week into the
  following weekend.

&&

.MESOSCALE...
Issued at 723 PM CDT Fri Aug 15 2025

MCS crossing the Mississippi River has begun weakening fairly
precipitously with warming cloud tops and a marked decrease in
lightning. While storms are weakening, there`s still a fairly
strong meso-high and cold pool which should be able to support
some strong wind gusts along the outflow that is surging out
ahead of the storms. While KMLI recent measured a 46kt gusts,
the gusts are expected to gradually diminish as cold pool/meso
high slowly weakens and as outflow further outpaces the
weakening convection. The threat of severe wind gusts into our
western CWA is decreasing, but plan to hang onto the severe
thunderstorm watch a bit longer to ensure the threat has indeed
ended.

- Izzi

&&

.DISCUSSION...
Issued at 321 PM CDT Fri Aug 15 2025

Through Saturday:

A cluster of strong thunderstorms recently developed west-
northwest of our area in parts of north central IA early this
afternoon in association with an MCV. This activity may tend to
weaken and slow some as it shifts eastward towards northwestern
IL later this afternoon as it begins to outrun the better
instability and the main driving impulse still residing west of
our area. However, in spite of this, we cannot rule out this
activity moving into far northwest parts of the area (in and
around the Rockford area) in the 7 to 9 pm timeframe with a
strong gusty wind and heavy rain threat.

Steepening mid-level lapse rates and increased moistening along
the nose of a veering west-southwesterly low-level jet later
this evening into tonight will likely foster additional
thunderstorm development with the approaching MCV disturbance as
it shifts into southern WI and northern IL. Accordingly, we
have opted to bump POPs up into the 30 to 50 percent range
across most of the area through the night. The main threats
from these storms tonight will continue to be strong gusty
winds (up to 60 mph) and torrential downpours. Some of this
activity may linger into early Saturday morning before the main
impulse shifts east of the area.

Considerable uncertainty continues regarding convective trends
and temperatures/heat indices Saturday afternoon owing to the
lingering impacts from the early morning convection. In spite of
this uncertainty, there are signals that the impulse over
southern WY late this afternoon may spark of additional showers
and thunderstorms Saturday afternoon as it tracks into our
region. We currently put the probabilities for these afternoon
storms at about 40%. Assuming these storms do materialize, 25-30
kt of effective bulk shear will support the potential for
multicell clusters capable of producing damaging wind gusts.
Torrential rainfall would also be possible with these storms,
which could result in localized flash flooding into Saturday
night, particularly in any areas that experience multiple rounds
of storms.

Outside of the storms, temperatures will be hot and humid on
Saturday. The combination of temperatures in the upper 80s to
the mid 90s (hottest south of I-80) will push peak heat index
values into the 95 to 105 Saturday afternoon. The hottest
temperatures and heat indices are expected to largely remain
south of I-80. Portions of this region could need a heat
advisory for Saturday afternoon, particularly if heat indices
top 105. While this remains plausible, we have opted to hold off
an any heat headline at this time. This was largely due to
lingering uncertainties in if convective trends tonight into
early Saturday morning impact temperature recovery during the
day.

KJB


Saturday Night through Friday:

The forecast for Saturday night through Sunday continues to be
one of lower confidence due to uncertainty in the coverage of
storms tonight and Saturday and where their respective outflow
boundary`s will set up. That said, the general thinking for
Saturday night is that a cluster of thunderstorms should develop
in southern WI and drift into the area overnight (if storms are
not already ongoing from Saturday afternoon) as a shortwave
disturbance rounds the ridge that will be centered over central
MO. Given that these storms should be generating along a
northwest-southeast oriented outflow boundary and shear vectors
will also be parallel to this boundary, there is a good chance
that storms will train over the same locations Saturday night
until the aforementioned wave exits. While there is uncertainty
as to where exactly the training convection will set up, the
nearly 2.0 inch PWATs will make these storms capable of
producing torrential rainfall which could result in flash
flooding.

Heading into Sunday, a lull should develop as the
aforementioned storms move out of the area after mid-morning on
Sunday. As the storms exit, they will force the outflow to surge
inland as a backdoor front. Exactly how far west this
outflow/front surges remains unclear at this time, but the
general thinking is that it should be near the Fox Valley by
Sunday afternoon. Given that this outflow/front looks to be the
main driver for any new thunderstorm development Sunday
afternoon, the bulk of any storms that do develop should be to
the west of this boundary (to the west of the Fox Valley).
However, forecast soundings do show a very weak cap developing
Sunday afternoon which may limit the coverage of storms. For now
have decided to maintain the previously advertised 20% POPs but
suspect a fair amount of dry hours will occur on Sunday
especially near the lake. Furthermore, any storms that do
develop will have the potential to produce gusty winds and
torrential rainfall which could result in flash flooding given
the 25-30 kts of shear and nearly 2.0 inch PWATs respectively.

Outside of the storms, Sunday will also be another warm and
humid day especially inland of the aforementioned front/outflow
boundary. Temperatures on Sunday are currently forecast to top
out in the lower to mid-90s (80s near the lake) and with dew
points forecast to be in the 70s, heat indices could once again
get into the 100-105F range inland of the lake. Though, if
storms develop prior to peak heating then these readings could
turn out to be lower than forecast. Regardless, those with
outdoor plans should take precautions to protect themselves from
the heat such as staying hydrated and taking frequent breaks in
the shade and/or air conditioning.

Broad troughing is forecast to develop across the Upper Midwest
Sunday night into Monday which is expected to push the ridge
southward into Gulf Coast through the middle of next week as the
trough moves into the Great Lakes. As a result, a cold front is
expected to move through the Great Lakes region Monday through
Tuesday bringing with it more chances for scatted showers and
thunderstorms. While the lingering humid air mass will likely
keep a heavy rain threat in play, the weakening wind shear does
look to lower the severe threat for Monday and Tuesday. With the
front generally forecast to exit our area Tuesday night rain
chances should taper by Wednesday morning, however, if the front
is slower to exit then a few showers/storms could develop south
of the Kankakee River Valley on Wednesday.

In the wake of the front, notably cooler and less humid
conditions are forecast to establish across the Great Lakes as
the broad troughing to our east generates northwest flow aloft.
Therefore, expect high temperatures to reside in the 80s from
the middle of next week into the following weekend with more
comfortable humidity levels (dew points in the 60s). While rain
chances behind this front look limited due to dryer mid-level
air, another front is forecast to dive into the Great Lakes
sometime next weekend which could result in a period of showers
and possibly thunderstorms but this is very low confidence at
this time.

Yack

&&

.AVIATION /00Z TAFS THROUGH 06Z SUNDAY/...
Issued at 653 PM CDT Fri Aug 15 2025

Forecast concerns include...

Chance of thunderstorms through the period.
Wind directions Saturday.
Possible mvfr cigs Saturday morning.

Current cluster of thunderstorms over far eastern IA is slowly
turning to the southeast early this evening. Confidence remains
low for how much further to the southeast it may turn as well as
how far to the east it may persist. Guidance trends from this
morning`s runs seem to have a better handle on this activity
than current model runs and they suggest a slow weakening trend
as it moves across west central IL. Current trends would suggest
the bulk of thunder would remain mainly south of terminals and
for now have included only prob shower mention for the Chicago
terminals but maintained prob thunder for RFD. There is an
outflow boundary ahead of this activity and that will need to be
monitored for a possible brief wind shift to the northwest.

Attention then shifts to another cluster of thunderstorms near
the Twin Cities. Model guidance seems to be handling this a bit
better and suggests an overall southeast turn tonight with this
activity likely reaching the terminals in the predawn hours to
around daybreak Saturday morning. Confidence is also low but
have adjusted prob thunder timing to better account for this
potential. Some guidance also redevelops thunderstorms across
far northeast IL/southern Lake Michigan and then into northwest
IN through mid morning Saturday. Its possible tempo thunder may
eventually be needed during this time period.

Convective trends for Saturday afternoon/evening are more
uncertain and dependent on the morning convection. If the
morning is active with thunderstorms, its possible that the
afternoon may be a lull in the precipitation with additional
thunderstorm chances Saturday night. Too much uncertainty to go
dry and maintained prob thunder, but adjusted it a few hours
later.

Generally southerly winds under 10kts are expected tonight,
possibly south/southwest at times. If thunderstorms do move
across the area early Saturday morning, a period of south/
southeast winds would be expected mid/late Saturday morning,
before turning back to the south/southwest. However, changes to
the wind forecasts can be expected based on convective trends.

Brief ifr/lifr cigs/vis can be expected with any strong
thunderstorms. If thunderstorms do move across the area Saturday
morning, there may be a period of low mvfr cigs near Lake
Michigan but confidence is also low. cms

&&

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

&&

$$

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