558 FXUS63 KIND 211629 AFDINDArea Forecast Discussion National Weather Service Indianapolis IN 1229 PM EDT Sun Sep 21 2025
.KEY MESSAGES...
- Scattered showers and thunderstorms today becoming numerous tonight
- Isolated severe storms with damaging winds possible this afternoon into early evening
- Milder with daily chances for showers and a few t-storms next week
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.FORECAST UPDATE... Issued at 1018 AM EDT Sun Sep 21 2025
Some mid level subsidence ahead of the next wave, partially observed on the 12Z ILX sounding and better observed on IND ACARs soundings has led to a decrease in coverage of precipitation across a majority of Indiana this morning. This should continue into the afternoon, with only isolated showers and a few thunderstorms, mostly due to a highly saturated PBL and weak low level lift. This also matches latest trends in the CAMs showing very little QPF west of I-69 this afternoon. Precipitation chances are still expected to ramp up overnight with isolated strong storms.
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.SHORT TERM (Today and tonight)... Issued at 306 AM EDT Sun Sep 21 2025
Central Indiana will remain under the influence of a large upper trough throughout the short term period. This will keep chances for showers and thunderstorms around.
Early This Morning...
An initial piece of upper energy is aiding scattered to numerous showers and a few thunderstorms moving northeast across the area this morning. These will continue to move northeast through the predawn hours and could bring some brief heavy rain to parts of the area.
Additional convection across western Kentucky is weakening, but will have to watch to see if any holds together to reach the southwest forecast area before 12Z.
Will generally have up to likely PoPs across the area to cover the above.
Today...
Will keep some lower PoPs around this morning in case weak forcing manages to spark some convection, but higher coverage of convection should occur this afternoon as additional weak forcing moves in during the peak of instability.
The weak forcing should keep coverage below the numerous (likely) category. Instability is decent but shear looks weak. Low level lapse rates will steepen up this afternoon. Soundings show dry low levels, and this has the potential to enhance downdrafts. Thus, feel an isolated severe storm with damaging winds is possible this afternoon.
Thanks to increased cloud cover, highs today will be a little cooler than previous days, with readings in the lower and middle 80s expected.
Tonight...
The afternoon`s convection may linger into the early evening before weakening/moving east of the area.
Forcing will ramp up overnight as an upper level jet moves to the northwest of the area, and upper heights fall as the upper trough moves closer. Moisture will be plentiful, with southwest winds bringing a flow of moisture into the area through the night.
Loss of heating will lower the lapse rates and should keep the isolated severe storm threat confined to early evening.
With the expected forcing and moisture, will go with likely category or higher PoPs most areas overnight.
Clouds/rain will keep temperatures in the 60s for lows.
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.LONG TERM (Monday through Saturday)... Issued at 306 AM EDT Sun Sep 21 2025
A much different week is expected this week than last, with near constant chances for showers and a few thunderstorms, and significantly milder temperatures.
Early in the week, a frontal zone will gradually sink into the region as multiple upper level disturbances move through the area, while a large upper closed low gradually develops and persists somewhere in the eastern half of the CONUS later in the week and into the weekend.
Differences in placement and movement of the upper low with time result in greater uncertainty and thus lower rain chances later in the week, but suffice to say rain chances will be present basically every period through at least Saturday. Total rainfall through the week may be enough to put a substantial dent in longer term rainfall deficits, though perhaps not enough to erase them completely.
Temperatures will be substantially cooler this week, particularly mid to late week, as a result of the closed low and associated cloud cover/precipitation, with max/min temperatures much nearer climatological normals in the mid 50s and mid 70s.
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.AVIATION (18Z TAF Issuance)... Issued at 1215 PM EDT Sun Sep 21 2025
Impacts:
- Scattered convection possible this evening - Numerous showers and some storms overnight and continue through tomorrow - MVFR ceilings possible tomorrow
Discussion:
The main area of showers and thunderstorms has moved off to the north. There is a chance for an isoalted shower this afternoon, but coverage was too low to include in the TAF at this time. Addtional showers and thunderstorms are possible this evening. More widespread showers will move in overnight tonight with occaisional MVFR VIS and CIGs
Drier low levels will keep prevailing ceilings outside of rain in VFR through 06Z Monday, then some MVFR ceilings may develop by 12Z Monday.
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.IND WATCHES/WARNINGS/ADVISORIES... None. &&
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UPDATE...Updike SHORT TERM...50 LONG TERM...Nield AVIATION...Updike
NWS IND Office Area Forecast Discussion