363 FXUS63 KIND 211043 AFDINDArea Forecast Discussion National Weather Service Indianapolis IN 643 AM 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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.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 (12Z TAF Issuance)... Issued at 642 AM EDT Sun Sep 21 2025
Impacts:
- Scattered convection continues at times through the day - More numerous showers and some storms overnight - Some fog early, mainly at KHUF - Wind gusts near 20kt this afternoon
Discussion:
Fog/stratus will linger early at KHUF and cannot be ruled out briefly at KLAF/KBMG very early in the period.
The main area of showers and thunderstorms will be north of the TAF sites by valid time, but isolated showers will persist early in the period. Additional scattered showers and a few thunderstorms will develop this afternoon and continue into early evening.
More widespread showers will move in overnight tonight.
Drier low levels will keep ceilings outside of convection 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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SHORT TERM...50 LONG TERM...Nield AVIATION...50
NWS IND Office Area Forecast Discussion