Peotone Weather
National Weather Service Forecast for: Peotone, IL
Issued by: National Weather Service Chicago/Romeoville, IL
Updated: Sat, 24-Jul-2021 2:42pm CDT

Peotone, IL
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The zone forecast data for ILZ108 (Eastern Will) will be displayed
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Partly Cloudy
Partly Cloudy


Mostly Sunny
Mostly Sunny

Partly Cloudy
Partly Cloudy

Thunder storm
Thunder storm

Partly Cloudy
Partly Cloudy

Partly Cloudy
Partly Cloudy
  Hi ≈90°F Hi >85°F Hi ≈90°F Hi ≈90°F Hi ≈85°F Hi <85°F Hi <85°F

Thunder storm
Thunder storm
Partly Cloudy
Partly Cloudy
Mostly Clear
Mostly Clear
Thunder storm
Thunder storm
Thunder storm
Thunder storm
Partly Cloudy
Partly Cloudy
Lo ≈70°F Lo >65°F Lo >65°F Lo ≈70°F Lo <75°F Lo ≈65°F Lo ≈65°F  


Partly cloudy with a 60 percent chance of showers and thunderstorms. Some thunderstorms may be severe. Lows around 70. Southwest winds 10 to 15 mph in the evening becoming west and decreasing to around 5 mph after midnight.
Partly cloudy. Hazy. Highs around 90. Northwest winds 5 to 10 mph.
Sunday Night
Partly cloudy in the evening then clearing. Lows in the upper 60s. Northwest winds 5 to 10 mph.
Sunny. Highs in the upper 80s. Northwest winds around 5 mph.
Monday Night
Clear. Lows in the upper 60s. South winds around 5 mph.
Mostly sunny. Highs around 90.
Tuesday Night
Mostly clear. Lows around 70.
Mostly sunny in the morning then becoming partly cloudy. Highs around 90.
Wednesday Night
Mostly clear in the evening, then partly cloudy with a 30 percent chance of showers and thunderstorms after midnight. Lows in the lower 70s.
Partly cloudy. A 30 percent chance of showers and thunderstorms. Highs in the mid 80s.
Thursday Night
Partly cloudy. A 30 percent chance of showers and thunderstorms. Lows in the mid 60s.
Partly cloudy. Highs in the lower 80s.
Friday Night
Partly cloudy. Lows in the mid 60s.
Partly cloudy. Highs in the lower 80s.


Forecast from NOAA-NWS for Peotone, IL. (Zone forecast for Eastern Will)

FXUS63 KLOT 241935

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
235 PM CDT Sat Jul 24 2021

1123 AM CDT

Only notable forecast update this morning was to bump PoPs up along
and south of I-80 through the late morning hours to account for a
few isentropic upglide/warm-air advection-driven showers that have
moved into LaSalle and Livingston counties. This activity is
expected to fade within the next hour or two. Otherwise, the overall
thinking regarding today`s forecast remains unchanged.

The earlier showers and storms across southern Minnesota, northeast
Iowa, and southern Wisconsin have faded as expected as they ran into
a considerable amount of convective inhibition. Outflow from this
activity is currently racing into southeast Wisconsin and
northeast Illinois, and may cause a few spotty showers and maybe
even a transient thunderstorm to sprout along it as it continues
southeastward, but poor lapse rates and a relative lack of upper-
level support for forcing as it outruns a modest mid-level
shortwave should prevent anything more substantial from developing
along this outflow.

The main timing for thunderstorms is still expected to come later
this afternoon and evening. Convective initiation is favored to
occur during the mid-afternoon hours after diurnal heating and the
aforementioned shortwave have had time to steepen lapse rates a bit.
Some guidance like the HRRR holds off on thunderstorms developing
until later in the afternoon, but a closer look reveals that
these models are overdoing the degree of mixing and hence
underdoing surface dew points, resulting in convective
temperatures not getting breached until later in the day. The
guidance that has a better handle on the low-mid 70s surface dew
points tends to start firing storms up across our northern
counties between 20 and 22Z.

The predominant threat with these storms still appears to be
damaging winds owing to 1000-1500 J/kg of DCAPE materializing by
the late afternoon. However, there is still some potential for
large hail and tornadoes later today as well, particularly if any
supercellular structures are able to form within what`s looking to
be a broken line of storms consisting of largely multi-cell and
bowing segment storm modes. PWATs pushing 2" will also support
torrential downpours within any storms that develop today, and the
efficient rainfall rates may lead to some localized minor flooding
occurring in some spots.



235 PM CDT

Through Sunday night...

The primary focus for today is on the potential for severe
thunderstorms. For information about that, please reference the AFD
update above and any subsequent mesoscale discussions that are
issued this afternoon and evening. A mesoscale discussion
covering at least the next few hours will be issued soon.

The hot and humid conditions are the other ongoing story of the day.
Current temperatures in the lower 90s and dew points as high as the
upper 70s are producing oppressive conditions across the region with
peak heat indices reaching triple digits in some spots. While the
thunderstorms that move through the area will cool things down for a
bit, there will be no reprieve from the soupy humidity until
tomorrow as dew points will only begin to fall at a good clip in
wake of the true cold frontal passage, which won`t occur until
overnight tonight. The new air mass being ushered in by the cold
front is not exactly going to be a cooler air mass. While some
degree of cloud cover is expected tomorrow, the strong late July Sun
will allow for us to warm up into the lower 90s again in most
locations. However, with dew points falling as low as the mid 50s by
mid-afternoon tomorrow, peak heat indices won`t be more than 2-3
degrees higher than tomorrow`s maximum temperatures in most cases.

While we should be precipitation-free tomorrow, HRRR-Smoke runs
suggest that a greater quantity of smoke will be transported into
the area tomorrow behind the aforementioned cold front. Some of
this smoke will likely be brought down closer to ground level,
resulting in hazy conditions across the area for yet another day.



235 PM CDT

Thinking regarding the forecast from Monday through Friday
remains unchanged, and the below discussion that was issued
overnight remains valid.

Monday through Friday...

July`s last full week will start hot with highs of 90 or a little
over for many communities Monday through Wednesday. High dew
points return Tuesday bringing potential for heat index readings
to near 100, mainly on Wednesday. A strong cold front is
projected on or near Thursday with potential for thunderstorms
just prior to and during that transition.

Weak high pressure of 1016 mb will be over the area Monday. With
light and variable winds, dew points will start nudging up, but
still favor the drier ECMWF over the GFS on Monday, as the GFS
just seems too moist for the setup. With ample sun Monday,
temperatures could overperform a couple more degrees, with some
93-94 readings possible. A lake breeze will develop Monday.

A 500 mb ridge of 597 dam will become established over the lee
side of the Rockies into the High Plains for Tuesday and
Wednesday, with disturbed northwest flow on its periphery into
the Great Lakes region. The focus for any convective initiation
looks at this time to be well north of the area Tuesday and into
the day Wednesday, anchored more toward the upper jet streak and
associated short waves, and by Wednesday also a developing
surface front. With low-level flow becoming southwesterly on
Tuesday, the high dew point reservoir to our south will be steered
back into the area, inevitably aided by evapotranspiration from
mature crops. This may make the air mass a little more difficult
to substantially heat (i.e. 93+ readings), as well as any
returning smoke from fires. Nonetheless, with 850 mb temperatures
of 19-22C predicted, hard to see why highs both Tuesday and
Wednesday would not reach lower 90s with very warm nights. The
signature for highest dew points (widespread mid 70s) is
Wednesday, and this is the day we will have to keep an eye on for
potential Heavy Advisory criteria.

The approach of the frontal system Wednesday night, as well as
south-southeast steering flow, result in increasing storm chances
and those continuing into Thursday due to model spread on timing.
Not surprisingly in such a pattern, the parameter space is there
for some severe threat in the Great Lakes region, including
possibly an MCS Wednesday Night, but far too away to hang one`s
hat on much at this time. The surface front continues to be more
agreed upon in global guidance over the past two days in shoving
southward through the area during Thursday. This looks to bring at
least a short episode of cooler temperatures and drier weather at
the end of next week (possibly later Thursday, likely Friday, and
possibly all of Saturday).



For the 18Z TAFs...

The primary concerns for the terminals continue to focus on the
favored timing for strong thunderstorms this afternoon.

A minor disturbance is currently shifting eastward across IL, and
is producing a few widely scattered showers south of the Chicago
area terminals. This activity is expected to remain south of the
terminals, but a few storms may develop into northwestern IN over
the next couple hours. Otherwise, our main attention this
afternoon is focused on a surface cold front, which is currently
extends northeastward from northeastern IA into the Green Bay, WI
area. Thunderstorms are expected to develop ahead of this front
after 3 PM as this front approaches southeastern WI. These storms
may develop right overhead, our just north of the terminals over
southern WI and far northern IL before tracking southeastward
across the area late this afternoon into the evening. The best
timing for these storms impacting the Chicago area terminals
continues to be in the 21 to 01z timeframe, with a slightly
earlier time at RFD. Strong northerly wind gusts, potentially in
excess of 50 kt will be possible with these strong storms as they
shift across the area.

The storms will end at the terminals after about 01z as they
shift south. However, the storms may continue to impact southward
departures and arrivals through the evening as they continue
shifting into central parts of IL and IN. The surface front will
lag the storms by a considerable amount. Before it passes, there
could to a few isolated or scattered showers or even a storm in
the early to mid evening near ORD and MDW, but confidence
continues to be very low with this possibility. Otherwise, there
is some potential for some reduced visibilities in fog late
tonight with diminishing low-level flow and continued high
moisture. On Sunday, the west-northwesterly winds will increase.





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NWS LOT Office Area Forecast Discussion