textproduct: Indianapolis

KEY MESSAGES

- Rain chances late this afternoon/evening north of I-70.

- Cooler but still mild on Friday and Saturday.

- Rain chances return Friday Night, with greatest chances expected Saturday night into Sunday.

- Mild and wetter pattern likely early-mid next week.

DISCUSSION (This evening through Thursday)

Issued at 312 PM EDT Thu Oct 29 2026

Rest of this afternoon and tonight...

Widely scattered convection has developed in the last couple of hours in northern portions of Indiana. This activity is along the edge of the primary theta-e ridge and on the southern periphery of an upper trough moving through the Great Lakes. Instability is meager at best, with SBCAPE values running 500 j/kg or less in a corridor extending SW from this activity into NE IL. CAMs have been all over the place with this activity with earlier runs of the HRRR more bullish than recent runs, and other CAMs such as the RRFS similarly backing off from the 00Z runs. Earlier had bumped up pops to chance with added isolated TS given forecast soundings showing just enough CAPE to warrant the inclusion. Present satellite indications are that southward development is underway across NE IL and this activity would move into the northern portions of central IN before diminishing between 00-02Z. In the wake of an associated cold front, winds will shift to the N-NE ushering in much drier air into central IN into early Friday.

Friday and Friday night...

Elevated convection will form tonight over the central Plains associated with a modest low level jet impinging on a stationary boundary. This activity is expected to shift eastward on Friday following the low level jet axis while weakening over IA and northern IL. Clouds associated with the anvil blow off from these storms combined with the large cirrus shield associated with southern stream shortwave trough approaching from the SW will lead to increasing clouds across central Indiana. In fact, it will be the start of many days of less sun that we've seen in quite some time. As a result of the increasing cloud cover, and weak CAA associated with high pressure centered over the eastern Great Lakes, high temps will be 5-10 degrees cooler than Thursday. By Friday night, there remains some signal that some of the remnant elevated convection, running on almost no instability, will shift into far NW portions of central IN. Therefore, have opted to carry low PoPs across this area starting after 06Z Saturday. Copious mid-high level clouds across the rest of central Indiana will keep overnight lows in the 50s.

Saturday into Sunday...

Light showers and/or sprinkles will be possible across northern portions of central Indiana associated with the remnant elevated convection. Otherwise, overcast skies are expected Saturday thanks to approaching, yet weakening, lead southern stream shortwave trough and copious mid-high level cloud cover. Due to the degree and thickness of cloud cover, high temperatures have been notched down a cat from previous forecast with temperatures struggling to get out of the 60s despite Sat morning lows in the 50s.

A secondary and stronger shortwave trough (currently just west of the Baja CA peninsula) will move E-NE across central Indiana Saturday night into Sunday. The OP Euro remains the outlier compared to the remainder of model guidance showing generally scattered light showers late Saturday night into Sunday morning. With the majority of model guidance showing between 0.25 and 0.50 inch of QPF (greater south), upgraded PoPs to likely seems the most prudent forecast.

Sunday night into Monday night...

There remains uncertainty in exactly how the phasing of the two shortwave troughs will occur over the intermountain west. Nonetheless, mid-upper level ridging is expected to commence in the wake of the shortwave trough that shifts east of the forecast area by early Monday. There is some signal given nearly saturated low levels and modest WAA that drizzle or light rain will develop and persist during this period so NBM low pops seem reasonable. High temps on Monday could easily be 1-2 cats cooler if low clouds and drizzle occur through the day.

Tuesday into Thursday....

The GFS has come in line with other medium range guidance showing a more progressive solution with the primary phased trough over the plains. Ahead of this trough, ridging will continue to build over the eastern CONUS. There is considerable uncertainty regarding how strong the ridge will build and therefore the speed of the upper trough over the Plains as it pushes towards the MS valley and central Indiana. Slower solutions suggest that any precip threat will hold off until late Wed, while faster solutions showing precip potential as early as Tuesday night. NBM seems overly aggressive with likely PoPs early Wednesday given this is still 6 days out. High temperatures are likely to be again well above normal in the 70s on Tuesday with greater uncertainty for Wed-Thurs based on timing/extent of precip. As far as the threat for TS and severe weather, the kinematics will be more than sufficient for some severe threat, however model soundings continue to suggest very poor lapse rates in the mid levels with little to no deep layer instability. For now, will maintain no mention of TS in the forecast.

AVIATION (18Z TAF Issuance)

Issued at 104 PM EDT Thu Oct 29 2026

Impacts:

- Gusty winds from SW diminishing late afternoon.

- Scattered showers in vicinity of KLAF/KIND late afternoon/early evening.

Discussion:

Gusty SW winds from 18-22 kt will continue this afternoon before diminishing this evening between 21-23Z with commencement of nocturnal cooling and approaching cold front. Wind shift associated with cold front will move across the terminals between 23-04Z (around 02Z at IND) with north wind speeds expected to be under 10 kts given the aforementioned nocturnal cooling limiting any gust potential.

Associated with the frontal passage prior to 02Z, there will be sufficient instability and forcing along and just ahead of the cold front that widely scattered convective showers are expected in the vicinity of KLAF and KIND. An isolated thunderstorm is also possible at KLAF, but chances are low enough to not warrant inclusion in the TAF.

In the wake of the cold front, a few hour window of lower VFR ceilings are expected to move across the terminals overnight before scattering out occurs after midnight. As high pressure builds into the Great Lakes through Friday, winds will shift to E-NE direction with increasing high clouds expected during Friday afternoon.

IND WATCHES/WARNINGS/ADVISORIES

None.