textproduct: Indianapolis

KEY MESSAGES

- Areas of fog possible this morning, locally dense fog cannot be ruled out near valleys or rivers

- Low rain chances return tonight, scattered to numerous showers and storms are expected on Wednesday

- Localized flash flooding is possible on Wednesday

- Turning generally milder and drier late week into the weekend, chance for showers and storms on Saturday

DISCUSSION (Today through Monday)

Issued at 301 AM EDT Tue Aug 18 2026

Today...

Surface high pressure across the region will provide quiet weather conditions. Light winds combined with damp soils from recent rainfall has led to fog development in some areas this morning. Locally dense fog cannot be completely ruled out near valleys or rivers through daybreak. Look for fog to quickly mix out in typical diurnal fashion after daybreak. Partly cloudy skies are then expected during the day under large scale subsidence. Weak cold air advection behind a cold front which moved through on Monday supports slightly cooler than normal highs in the upper 70s to low 80s today.

Tonight through Wednesday night...

Embedded shortwaves within longwave troughing aloft will provide opportunities for convection towards the middle of this week. Low rain chances return as early as tonight with an approaching disturbance. Most guidance generally suggest lingering subsidence induced dry air from the departing surface high late today greatly limits the potential for precipitation. This along with marginal forcing in place keeps POPs around 20 percent or lower through the overnight. Expect greater rain chances during the day Wednesday once stronger forcing and deeper moisture returns. Model variability leads to some uncertainty regarding convective coverage. However, daytime heating and an embedded shortwave moving across an abundantly moist environment favors at least scattered convection by the afternoon.

Severe weather is not expected due to limited instability. Steep low- level lapse rates and DCAPE values approaching 600 to 700 J/KG could still result in a few strong sub-severe wind gusts. An isolated damaging wind gust cannot be entirely ruled out if sufficient destabilization occurs. The greater concern appears to be localized flash flooding given soils remain saturated from recent rainfall. Model guidance also suggest the potential for training storms as a weak west to east oriented cold front slowly pushes south late in the day. The weak surface boundary meandering and another embedded shortwave moving through keeps precipitation chances in the forecast overnight. Loss of daytime heating should result in less convective coverage though.

Thursday through early next week...

A weak frontal boundary meandering near south-central Indiana on Thursday will keep low precipitation chances in the forecast. Further north, surface high pressure begins to build in providing mostly quiet weather conditions. Look for the surface high to build further south Thursday night into Friday resulting in quiet weather conditions. Another embedded disturbance moves in on Saturday supporting at least low rain chances with sufficient moisture advecting into central Indiana. Long range guidance generally depicts surface high pressure building in once again late weekend into early next week. Large scale subsidence supports mundane weather conditions.

AVIATION (06Z TAF Issuance)

Issued at 108 AM EDT Tue Aug 18 2026

Impacts:

- Patchy fog this morning

Discussion:

Light northwesterly winds this morning along with damp soils from prior rainfall will promote patchy fog development at the outlying TAF sites between 07-13Z. Look for winds to remain light through the period. NW winds will become westerly later today and eventually S/SW this evening into tonight.

IND WATCHES/WARNINGS/ADVISORIES

None.