textproduct: Indianapolis

KEY MESSAGES

- Hotter and more humid air arrives Sunday and persists through much of next week

- Isolated thunderstorms may return mid to late week next week

DISCUSSION (This evening through Saturday)

Issued at 250 PM EDT Sat Aug 29 2026

Deep high pressure across the southern Mississippi Valley, embedded within an Omega Block pattern will keep broad ridging across the eastern CONUS through much of the forecast period. Despite the stagnate upper level pattern, the overall forecast will fluctuate some as low level disturbances develop over the upper Mississippi Valley this weekend into next week.

Initially, temperatures will remain seasonal as the ridge axis remains to the west, thus highs today are expected to be in the low to mid 80s with lows in the low 60s overnight. Also of note will be an increase in cloud cover over the Ohio Valley today through tonight. An 850mb jet will aid in maintaining convection as it moves into the Great Lakes region. Upper level cloud debris will spill over into the region, leading to 50-70 percent upper level cloud cover by this evening. With the ridge still strongly established, a majority of this convection will likely dissipate as it nears the Indiana area, but a few isolated cells could reach NW portions of central Indiana tonight. PoPs have been kept at 10 percent or lower, but may warrant an increase if observations dictate.

The low level troughing associated with the 850mb jet will become more diffuse as it pushes deeper into the upper high, but will still have enough organization to push the low level flow towards southerly. In return, temperatures will increase Sunday through mid week, starting in the upper 80s and reaching the low to mid 90s by Wednesday. This in combination with increasing dew points towards the upper 60s to low 70s will push heat index values near 100 during the middle of next week. Heat advisories will be likely over portions of central Indiana next week, but there are still some uncertainties with maximum daily temperatures (see next paragraph).

The main source of uncertainty will be the amplitude of the aforementioned ridge over the lower Great Lakes and Ohio Valley. WAA Sunday and Monday should aid in building the ridge some, but diabatic processes from upstream convection and upper level water vapor will mitigate pressure rises. Confidence in convection on the northern periphery of the ridge is high, but how far south this area of convection reaches is where confidence wanes. Currently the expectation is for a majority of any precipitation next week to remain north of the area, but the margin for error is small. Any rainfall and associated cloud cover that does occur will limit diurnal temperature gains, thus temperature gradients across the state could be significant some days.

AVIATION (00Z TAF Issuance)

Issued at 652 PM EDT Sat Aug 29 2026

Impacts:

- None expected

Discussion:

High level clouds will continue through much of the period, with scattered to perhaps broken mid clouds above 10000FT. A few cumulus are possible on Sunday.

An area of showers across northeast Illinois will continue to weaken as it moves into drier air, so no impacts are expected from it this evening. Sprinkles may move in overnight near KLAF.

Clouds should help keep fog at bay overnight, but there is a nonzero chance of fog, mainly at KHUF and KBMG.

IND WATCHES/WARNINGS/ADVISORIES

None.