Chester, Indiana Weather Forecast Discussion

125
FXUS61 KILN 210538
AFDILN
Area Forecast Discussion
National Weather Service Wilmington OH
138 AM EDT Sun Sep 21 2025
.SYNOPSIS...
Rain and storm chances return today and will continue on and off
through at least midweek. A stagnant pattern is likely to evolve
toward the end of the week as well, with periodic chances for rain
lingering into next weekend. Above normal temperatures will continue
through early this week before a wetter and cooler pattern develops
midweek and beyond.
&&
.NEAR TERM /THROUGH TODAY/...
Mainly dry conditions should prevail in the local area through
sunrise with a gradual increase in overall cloud cover toward
daybreak and beyond. With light SE sfc flow setting up and a bit
more in the way of better LL moisture, temps will be a few degrees
warmer early this morning than has been the case recently, with lows
bottoming out in the lower to mid 60s.
Deeper moisture will advect into the local area this morning into
the afternoon, with broad SW flow becoming established with the
approach of a midlevel S/W into the daytime. Forcing will increase
rather abruptly into the afternoon, with an expectation for scattered
SHRA/TSRA to develop and move to the NE from this afternoon through
early evening. Some moderate instby (MLCAPE ~1200 J/kg), combined
with sufficient deep-layer flow/shear to support some organization,
will promote several multicell clusters to develop and become the
predominant storm mode by mid afternoon. Isolated gusty winds will be
possible in the strongest activity given the relatively supportive
LL thermodynamic environment (DCAPE approaching 1000 J/kg) and modest
shear contributing to weak linear organization with the storms. Given
this setup, a severe storm or two cannot be completely ruled out.
The environment and forcing should be fairly uniform across the local
area, so this activity will be possible just about anywhere through
the heart of the daytime, although it should be most widespread
near/E of I-75 by early evening. Loss of diurnally-driven instby (as
well as stabilizing effect of earlier storms) toward/past sunset
should yield a decrease in coverage of activity toward late evening.
This being said, with the primary trof axis still hanging back to
the W, some forcing will remain in place amidst an amply-saturated
environment overnight into Monday morning, so some ISO SHRA may
linger through tonight into Monday morning, particularly near/W of
I-75.
Highs today will still be above normal (lower 80s W to around 90
degrees E), but should be several degrees cooler than has been the
case in the recent pattern, owing to more widespread cloud cover and
SCT afternoon SHRA/TSRA. SW winds of 10-15kts will gust close to
20kts at times this afternoon outside of storms.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
There will certainly be a decrease in coverage of SHRA tonight owing
to a temporary reduction in forcing and large-scale ascent, as well
as loss of diurnally-enhanced instby. However, a few SHRA may linger
during the overnight, particularly toward daybreak in EC IN and WC
OH. Temps again dip into the lower to mid 60s amidst scattered to
broken sky cover tonight, with clearer skies favored SE of I-71.
Large-scale ascent due to more robust jet dynamics will increase
through the day Monday amidst continued moisture advection and PWs
trending well above normal. Amidst an uncapped environment, SCT to
numerous SHRA/TSRA are expected by mid morning through the remainder
of the short term period, with several rounds of activity possible
for any one location. Coverage should be maximized during the
afternoon and evening, alongside an accompanying low-end severe risk
once again. A few strong storms with gusty winds will be possible,
with an ISO severe storm possible. However, most locales will simply
receive some much-needed rainfall (with potential of an inch or more
in some spots) along with some rumbles from time-to-time. But the
rainy/stormy day Monday will certainly be a departure from the recent
pattern of dry conditions and ample sunshine.
Highs Monday top out in the upper 70s in WC OH to mid 80s in the
lower Scioto Valley and NE KY.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
QPF maximum expected Monday night in our fa as the base of the
shortwave trough ejects through the Ohio Valley. CAPE will gradually
diminish overnight, but there still may be some convection around
that will help with some localized enhancements in rainfall. Given
the extremely dry antecedent soil conditions, hydro concerns remain
very limited.
Synoptically, an elongated longwave trough covers a large portion of
the central and eastern CONUS. Global models remain in agreement
that this troughing feature remains intact across the Ohio Valley
through the entire work week, but does become modified in
shape/orientation over time. The modification and placement of this
trough will certainly have an impact on rain chances, but also
influence humidity and temperature values. Based on latest guidance,
the ILN fa does remain on the eastern periphery of the mean trough
axis through at least the middle of the work week. This will keep a
southwesterly flow pattern intact and thus usher in a more humid air
mass. The trough remains very slow to propagate eastward, so we may
not be on the back end of this trough through the entire forecast
period (which would provide cooler/drier air and lower chances for
rain). Thus, daily rain chances remain possible during the entire
extended forecast period given this synoptic pattern. However, this
does not necessarily mean that everyone will observe measurable
rainfall each day.
High temperatures will trend near normal during the beginning of the
work week, but may dip a few degrees below normals near the end of
the week as the base of the longwave trough will be in closer
proximity to us.
&&
.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
VFR conditions will continue through the morning hours with the
exception of some brief MVFR VSBYs at KLUK due to river valley BR
around daybreak. Winds around 5kts or less will increase by mid
morning through the afternoon out of the SW to 10-15kts, with gusts
to 20kts possible outside of SHRA/TSRA. Southerly winds at 5kts or
less are expected once again by the end of the period.
The main item of interest for today is going to be SCT SHRA/TSRA by
the afternoon, with PROB30s included for each of the sites to account
for the potential. Was not confident enough to add a TEMPO in just
yet, but certainly it may eventually be warranted for a few of the
sites. The main concern with this activity is going to be sudden
changes in wind speed/direction as well as VSBY.
Coverage of activity will decrease toward/beyond 00z, although
certainly some ISO SHRA may linger at times through daybreak Monday.
OUTLOOK...Thunderstorms are possible through Thursday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...KC
NEAR TERM...KC
SHORT TERM...KC
LONG TERM...Clark
AVIATION...KC

NWS ILN Office Area Forecast Discussion