textproduct: Indianapolis

KEY MESSAGES

- Heat Advisory in effect for all of central Indiana from Tuesday afternoon through Thursday evening

- Increasingly hot and humid conditions through the middle of this week. Heat index values on Tuesday and Wednesday may reach the low 100s.

- Isolated to scattered thunderstorms will be possible at times Thursday through the weekend.

FORECAST UPDATE

Issued at 956 AM EDT Mon Aug 31 2026

The forecast remains in good shape with only minor adjustments needed. Upper ridging and surface high pressure centered south of the region will continue to promote dry weather conditions with partly cloudy skies. Southwest flow around the surface high will promote warming temperatures today. Look for highs generally in the upper 80s to low 90s across much of central Indiana. A subtle mid- upper level impulse tracking along the northern periphery of the ridge will enhance cloud cover at times, mainly across the northern half of the area.

DISCUSSION (Today through Sunday)

Issued at 241 AM EDT Mon Aug 31 2026

Surface analysis early this morning shows strong high pressure off the Carolina coast, providing warm and humid southerly flow within the lower levels. A frontal boundary was found from western MN across NB to KS and the TX panhandle. Aloft, water vapor showed ridging in place over upper midwest. a plume of tropical moisture continued to stream across the American SW to NB and MN before diving SE to IN/OH and NY. This upper level moisture continued to produce the high cloud cover across Central Indiana.

Today and Tonight...

More dry weather is expected today and tonight as forecast soundings suggest dry lower and middle levels with the warm but humid S-SW flow in place. Forecast soundings show the upper level moisture continuing to linger across the area through the day, but clearing tonight as the steering flow aloft becomes more westerly, pushing those high clouds across the Great Lakes instead of into Indiana. Thus a partly sunny day and a mostly clear night will be expected. Again highs around 90, persistence, will be expected. Warmer temps will be possible across southern parts of Central Indiana where cloud cover will be less substantial.

Tuesday and Wednesday...

Hot and humid weather looks in store for both Tuesday and Wednesday. Strong upper level high pressure will be stretching across the southern plains and Ohio Valley, keeping cloud cover and the upper flow across the Great Lakes. Forecast soundings on both days suggest a very dry and very hot column, with 700mb temps near 12C. Surface high pressure anchored over the southeastern states will continue to provide hot and humid southerly flow. 850mb temps near 22C will allow for highs in the mid 90s on Tuesday and Wednesday. Should this stay the course, Heat advisories will be needed.

Thursday through Friday...

Weak ridging within the upper flow is expected to build across the upper midwest, allowing NW flow to begin to develop across Central Indiana by Friday. Strong upper level high pressure will be centered over KS and MO. A weak wave is suggested to pass across northern Indiana on Thursday, followed by a stronger wave on Friday afternoon into Friday Night.

A weak frontal boundary will be in the vicinity of Central Indiana on Thursday, passing south of our area on Friday Night. This along with an expected hot, humid and unstable air mass in place will continue the need for at least chance pops during that time.

Saturday and Sunday...

The strong upper level high pressure system is suggested to strengthen and retrograde west on Saturday into Sunday, centering over western KS and eastern CO. This will result in a strong ridge over the CONUS, with monsoon like Pacific flow arriving over So Cal and NV before shooting north to Montana and Central CA before before turning quickly south the western Great Lakes into Indiana. Again, embedded waves within this flow are expected to ridge ride to Indiana, providing some upper support. Lee Side flow will provide some subsidence across the eastern Great Lakes, resulting in a stronger surface high there, and should the earlier front make it far south, cooler easterly flow arriving across Central Indiana for Saturday and Sunday. At the moment, forecast soundings show best saturation on Saturday Night, with a cooler and dry sounding on Sunday. Thus for now, pops will be needed on Saturday and Saturday Night, and confidence remains low for Sunday.

AVIATION (18Z TAF Issuance)

Issued at 116 PM EDT Mon Aug 31 2026

Impacts:

- Occasional southwesterly wind gusts between 16-22 kt this afternoon, primarily near KIND

Discussion:

VFR conditions are expected through the period with high pressure remaining dominant. Southwesterly winds will generally remain around or below 10 kt, but occasional wind gusts up to 16-22 kt are possible this afternoon.

IND WATCHES/WARNINGS/ADVISORIES

Heat Advisory from 2 PM Tuesday to 8 PM EDT Thursday for INZ021- 028>031-035>049-051>057-060>065-067>072.