Chesterfield, Indiana Weather Forecast Discussion

215
FXUS63 KIND 200135
AFDIND
Area Forecast Discussion
National Weather Service Indianapolis IN
935 PM EDT Fri Sep 19 2025
.KEY MESSAGES...
- Very warm temperatures persist into Saturday
- Chances for showers and a few thunderstorms arrive as early as
  late tonight into Saturday
- Milder conditions Sunday onward with daily potential for showers
  and storms next week
&&
.FORECAST UPDATE...
Issued at 935 PM EDT Fri Sep 19 2025
Only minor changes to the forecast with this update. First, added
more weight to short-term high-resolution guidance to better capture
the rapid post-sunset drop in temperatures that observations are
showing. Second, trimmed back PoPs a bit since recent radar
presentation has not been impressive and various CAMs are less
enthusiastic about precipitation overnight. Kept at least slight
PoPs across our western and northwestern counties, however, as weak
large-scale forcing arrives overnight. Some shower/storm
redevelopment is possible but should remain isolated in nature.
&&
.SHORT TERM (This evening through Saturday)...
Issued at 317 PM EDT Fri Sep 19 2025
The first rainfall chances in several days will move into the area
later tonight as an upper level low that has been blocked to our
west finally progresses eastward toward the region.
A few showers and perhaps a thunderstorm will be possible after
about midnight tonight, and chances will linger into Saturday as the
trough axis sits overhead and modest instability develops, though
coverage and intensity should be limited. Better precipitation
chances will hold off until the long term as moisture transport into
the region will be fairly weak until at least early Sunday.
Low level temperatures and thicknesses suggest one more quite warm
day on Saturday despite the increasing cloud cover and precipitation
chances, with highs climbing into the mid to upper 80s across the
area.
&&
.LONG TERM (Saturday night through Friday)...
Issued at 317 PM EDT Fri Sep 19 2025
A fairly dramatic pattern shift will continue into the long term as
the blocking ridge that brought dry and hot weather this week will
be replaced by two upper level waves that look to merge into a large
closed low that will persist somewhere across the region into the
eastern CONUS throughout much of next week.
This will lead to significantly milder temperatures and and an
unsettled forecast with daily chances for showers and a few
thunderstorms.
Model differences in the handling of this upper low do result in
lower precipitation chances with time due to increasing uncertainty,
but chances will be necessary most basically every period during the
long term, with thunder probabilities largely diurnally driven.
Probability matched mean progs and model precipitable water values
suggest a couple of periods, especially Sunday into Monday, when
some more widespread showers will be possible, along with brief
heavy downpours as PWAT values exceed climatological 90th
percentile. Total rainfall through the period may be enough to put a
dent in recently intensified drought conditions locally, though
likely not quite enough to completely erase long term moisture
deficits that now run as high as 5 or more inches in spots over the
past 60-90 days.
Temperatures will be as much as 10 to 15 degrees cooler next week,
depending upon the position of the low, as the exact position will
determine degree of cloud cover and precipitation, which will
significantly impact the resultant insolation.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 733 PM EDT Fri Sep 19 2025
Impacts:
- Scattered showers and thunderstorms after 19z Saturday.
Discussion:
VFR conditions expected through tonight.
Clouds have increased over the past few hours and will continue to
do so. Most terminals have a BKN to OVC deck at 25k ft. Expect
ceilings to lower through the course of the night. A few showers are
possible by LAF overnight as well.
Shower and eventually thunderstorm probabilities increase during the
day on Saturday, especially after 19z. Most terminals will have a
chance of seeing a storm, with the best probabilities (40 percent)
near LAF...lower probabilities elsewhere.
Winds will remain light and variable tonight, becoming southerly
during the day Saturday and remaining under 10kt.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Eckhoff
SHORT TERM...Nield
LONG TERM...Nield
AVIATION...Eckhoff

NWS IND Office Area Forecast Discussion