Peotone Weather

National Weather Service Forecast for: 2 Miles SE Peotone, IL Issued by: National Weather Service Chicago/Romeoville, IL

Updated: Tue, 03-Oct-2023 6:50am CDT

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Peotone, IL

Today Sunny Wednesday Partly Sunny Thursday Showers And T-Storms Friday Chance Rain Showers Saturday Slight Chance Rain Showers Sunday Mostly Sunny Columbus Day Mostly Sunny   Hi 87 °F ↓ Hi 82 °F ↓ Hi 72 °F Hi 61 °F Hi 55 °F Hi 56 °F Hi 59 °F     Tonight Mostly Cloudy Wednesday Night Showers And T-Storms Thursday Night Chance Showers And T-Storms Friday Night Chance Rain Showers Saturday Night Mostly Clear Sunday Night Partly Cloudy Monday Night Partly Cloudy   Lo 66 °F Lo 62 °F Lo 50 °F Lo 42 °F Lo 37 °F Lo 39 °F Lo 40 °F

Forecast from NOAA-NWS for 2 Miles SE Peotone, IL.

000
FXUS63 KLOT 031038
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
538 AM CDT Tue Oct 3 2023

.SHORT TERM...
Issued at 311 AM CDT Tue Oct 3 2023

Through Thursday...

Today will be another unseasonably warm day with most guidance
showing 925mb temps 1-2C warmer than Monday. While some high
cloudiness could filter sunshine a bit this afternoon, still seems
likely that temps will end up at least a degree or two warmer than
Monday, mostly in the mid-upper 80s. A stout enough south wind
should result in warm right up to the lakefront, with the one
possible exception being some slight lake cooling along the Lake
Co. IL shoreline this afternoon.

Increasing mid-high level cloudiness combined with a tighter
gradient keeping south winds up around 10 mph tonight, will likely
result in an even warmer night tonight than the past couple of
nights. Lows may struggle to get below 70 in the Chicago urban
heat island with mid-upper 60 across most of the CWA. Just to
offer up some perspective, normal highs this time of year are in
the upper 60s.

Upper ridge responsible for our recent warmth will begin to move
eastward over the next 24-48 hours which will allow a bifurcated
upper trough to make some eastward progress. There are some
differences in guidance in handling of this trough, likely due in
part to how/how much the northern stream shortwave interacts with
the southern stream shortwave. This does lead to some differences
to our sensible weather, mainly with respect to timing of rain
chances ending Thursday.

Temperature-wise, Wednesday should be another unseasonably warm
day, particularly southeast half or so of the CWA where some
filtered sunshine is possible. Given the very warm start to the
day and gusty southwest winds, it shouldn`t be too hard for highs
to get into the 80s near and southeast I-55. Farther northwest,
thicker cloud cover and possibly some afternoon showers should
keep temps a bit cooler (but still well above average).

A wave or two of showers and possibly a couple thunderstorms are
expected to impact the CWA sometime in the Wednesday afternoon
through Thursday time frame. GFS and NAM are slower with the upper
trough`s eastward progression and hang up the surface front
resulting in a more prolonged rain event that lingers into the
afternoon Thursday. ECMWF and GEM are more progressive with the
trough and front and would favor rain ending from the northwest
overnight Wednesday night into Thursday morning. Given the model
spread, didn`t make any adjustments to NBM POPs Thursday, but if
the more progressive solutions pan out then much of the day
Thursday will end up dry, especially northwest of I-55.

Mid level lapse and resultant instability should be on the lower
end of the spectrum, but most guidance does still have a few
hundred J/Kg of MUCAPE, which certainly is enough to justify at
least a chance of thunderstorms. There`s pretty good model
agreement that a jet streak emanating from the southern stream
trough will translate quickly northeastward across the region
Wednesday night. Pretty significant differences between ECMWF and
GFS with GFS showing a ~145kt h250 jet streak with ECMWF closer to
115kt at h250. It is probably worth acknowledging that if things
fall into place just right, then there could be a locally heavy
rainfall threat Wednesday night into Thursday morning. This would
hinge on the front/trough moving more slowly and the stronger jet
streak and associated frontogenetic circulation solutions verifying.

- Izzi

&&

.LONG TERM...
Issued at 311 AM CDT Tue Oct 3 2023

Thursday night through Monday...

Key Forecast Messages:

* Windy and much cooler on Friday with scattered showers possible
  in the afternoon into the evening

* Lake effect showers Friday night into Saturday into parts of
  northwest Indiana could be heavy at times with embedded
  thunderstorms

A majority of the model guidance dries things out pretty quickly
on Thursday night. That said, there remains some timing difference
in the cold front passage, with a slower fropa likely to hold
back a sliver of limited instability into the evening that could
keep the threat for scattered showers and maybe a thunderstorm
going for the southeast ~1/3 of the CWA.

On Friday-Friday evening, a deep mid-upper level trough will pivot
overhead, with a secondary cold front approaching at the surface.
Stout mid-level height falls should compensate for the much drier
low-level air mass to generate widely scattered showers, with some
upside potential coverage wise if there`s a bit more moisture
available. Steepening low to mid-level lapse rates from the
strong cold advection suggest low topped convective showers and
even some potential for graupel in more robust cores, given the
low freezing levels that will be in place. Shower activity should
peak during the afternoon with daytime heating and then wane in
the evening. Aside from the shower potential, blustery northwest
winds gusting up to 30 mph and highs in the upper 50s to mid 60s
will add to the fall-like feel.

Attention will then turn to what at this vantage point appears to
be an impressive lake effect rain setup for parts of northwest
Indiana and southwest lower Michigan. The current forecast winds
(and convergence orientation) from northwest to north-northwest
should favor northeastern Lake County IN and particularly Porter
County. With the open lake buoys still in the mid to upper 60s and
850 mb temps plunging to near 0C, lake surface to 850 mb delta T
will be near 20C, lake induced equilibrium levels forecast to push
25kft, and lake induced CAPE up to 1500 J/kg, if not a bit
higher. These all check boxes for heavy rain in a single dominant
band (if that occurs) and embedded thunderstorms, warranting the
inclusion of slight chance thunder mention. The height of the lake
effect rain should be later Friday evening into Saturday morning,
followed by decreased intensity during the afternoon and through
Saturday night as ELs diminish.

For the rest of the CWA, the main story later Friday night and
through the weekend will be the continued much cooler, autumnal
air mass. Lows will dip into the low-mid 40s Friday night and then
highs on Saturday will only be in the mid-upper 50s with a
healthy strato-Cu deck and blustery northwesterly winds. Cyclonic
flow aloft on the back-side of the trough and a just tight enough
pressure gradient may limit the threat for frost Saturday night
into early Sunday, but the air mass will still support lows in the
mid to upper 30s outside of Chicago and the immediate lakefront.
Sunday will be similar to Saturday except with winds a bit
lighter. A slow moderating trend will then begin to start next
work week.

Castro

&&

.AVIATION...
Issued at 538 AM CDT Tue Oct 3 2023
For the 12Z TAFs...

Concerns:

* None of significance.

Dry, VFR conditions will prevail through the current 24-30 hour
TAF period. Light southerly winds early this morning will increase
by the late morning to near/around 10 kt from a 180-200 degree
direction, with at least occasional 15-20 kt gusts at RFD this
afternoon. On Wednesday morning, expect 10-15 kt south-southwest
winds (190-210 deg) gusting up to ~20 kt by 14-15z.

Castro

&&

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

$$

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