580 FXUS63 KIND 230730 AFDINDArea Forecast Discussion National Weather Service Indianapolis IN 330 AM EDT Tue Sep 23 2025
.KEY MESSAGES...
- Dense fog this morning
- Milder with daily chances for showers and a few thunderstorms through Thursday
- Dry yet warm Friday into next week
&&
.SHORT TERM (Today and tonight)... Issued at 329 AM EDT Tue Sep 23 2025
Early This Morning...
Fog continues to expand across central Indiana with many sites are already near or at one quarter of a mile. This will continue through the remainder of the predawn hours, but there may be some variability at times. Will let the Dense Fog Advisory continue as is.
Rain showers have been staying just south of the forecast area, so will keep a dry forecast.
Today...
The fog will gradually mix out this morning. Current advisory is through 9 AM, but this may have to be extended per latest hourly guidance. Will keep a close eye and adjust if necessary.
Clouds may linger for a while as the fog mixes out, the clouds from an approaching system will be on the increase. Thus, there may not be a lot of sunshine today.
Thunderstorms to the northwest of the area overnight should dissipate before reaching the area this morning. However, outflow from these may reach portions of the northwest forecast area this afternoon. Some weak forcing from an upper wave may interact with this to produce some showers or storms. Will have some PoPs north to account for this.
High temperatures will depend on how fast morning clouds break up and how fast the arrival of clouds this afternoon occurs. Readings could reach the lower 80s if enough sun gets through.
Tonight...
Better chances for rain arrive tonight as some stronger upper energy moves in from the west. Moisture will be plentiful with 850mb winds still bringing in moisture from the southwest. The forcing and moisture should be enough to go with likely or higher PoPs most areas overnight.
The orientation of the 850mb winds should keep the highest rainfall amounts south of central Indiana, but far southern areas have the potential for some locally heavy rain. HREF Probability Matched Means show near 2 inches possible there.
Lows will be in the 60s thanks to rain and clouds.
&&
.LONG TERM (Wednesday through Monday)... Issued at 329 AM EDT Tue Sep 23 2025
Wednesday through Thursday Night...
Broad and multi-faceted upper trough will begin its final act for Indiana as the long term starts. This elongated, positively-tilted and very slowly progressing wave will likely induce weak surface low pressure near the local region Wednesday into Wednesday night. Corresponding increasing chances and amounts of rainfall should be focused near and south of the I-70 corridor, with the quasi-stationary short wave...possibly allowing additional widespread 1.00 to 1.50 inches of rain in these areas, and mainly moderate rainfall amounts farther north/northwest. At least isolated thunder could include a few strong storms over mainly southern portions of Indiana, through generally late day hours...after the surface circulation has had a chance to advect unseasonably high dewpoints into southern counties, and better wind shear arrives with the upper wave.
Lingering rain chances into Thursday reflect what should be drizzle and a few lighter showers as the trough axis finally crosses the Hoosier state. Near to slightly below normal afternoon highs in the low to mid-70s will be the rule thanks to considerable cloudiness...and light easterly breezes that will back to northwesterly as the surface trough departs. At least moderate humidity Wednesday...will begin to transition to more seasonable levels Wednesday night amid the backed flow. Overnight lows will consequently trend from around 60F Wednesday night to about 5 degrees lower by dawn Friday.
Friday through Monday...
Like a flipped switch...central Indiana will quietly return to what will likely be an extended dry period starting Friday. To the south of an increasingly active northern jet across southern Canada...will be another subtropical upper ridge, building northward into the Midwest for the weekend. Although, at least through the long term period, often light northwest or northeasterly breezes will mitigate potential heat under the 570 dm 1000-500 thickness.
Friday will be the mildest (ample-sun) day, as weak high pressure under a zonal ridge brings mid-70s for most of the CWA. Light westerly breezes Saturday, courtesy of a storm system crossing southern Canada, should return highs to around 80F. Reestablishment of surface high pressure early next week over the southern Great Lakes should help maintain near normal overnights and more warm afternoons around 80F amid lighter northeasterly flow under mostly sunny skies. The normal max/min at Indianapolis through the long term period is 74/53.
&&
.AVIATION (06Z TAF Issuance)... Issued at 1157 PM EDT Mon Sep 22 2025
Impacts:
- Fog developing for all TAF sites...locally dense
Discussion:
Widespread fog development is expected across central Indiana tonight...with variations possible through all flight rules. Mid to high clouds slowly crossing mainly southern portions of the region with the corresponding upper wave may partially mitigate fog intensity at times. Following a rainy Monday, now near-zero dewpoint depressions and mainly calm winds are providing higher confidence in fog developing and thickening through pre-dawn hours.
While lower confidence continues for flight rules prior to 08Z when initial fog development may yield visibility fluctuations...IFR/LIFR VIS and/or CIGs is expected at KLAF/KHUF/KBMG during the 07Z-12Z period. MVFR/IFR is more likely at KIND, yet brief LIFR cannot be ruled out either.
FG/FG+ may be slow to lift/dissipate Tuesday morning...with MVFR conditions potentially until 14Z-16Z at KLAF/KHUF/KBMG. FG will likely lift to MVFR stratus...before scattering to VFR by 18Z. Near-calm winds will continue overnight...then become southerly around 5KT after dawn.
&&
.IND WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 9 AM EDT this morning for INZ021- 028>031-035>049-051>057-060>065-067>072.
&&
$$
SHORT TERM...50 LONG TERM...AGM AVIATION...AGM
NWS IND Office Area Forecast Discussion