textproduct: Indianapolis

KEY MESSAGES

- Very warm through Tuesday with highs in the mid to upper 80s

- Scattered severe storms possible both Monday and Tuesday with damaging winds, large hail and localized flooding

- Storms will end Wednesday as the front shifts south, but unsettled weather may return late week into next weekend

DISCUSSION (Today through Saturday)

Issued at 250 AM EDT Sun May 17 2026

A deep upper level trough will develop across the Intermountain West by early in the week promoting an amp-lified regime aloft and downstream ridging over the eastern part of the country. This will bring a very warm and unstable airmass into the Ohio Valley today through the first half of the upcoming week. The ridge will gradually flatten as the trough shifts east enabling a strong cold front to track into the region by late Tuesday. While there will be periodic chances for thunderstorms throughout the first half of the week...the greatest potential for severe weather and heavy rainfall will come Tuesday afternoon and night as a strong cold front crosses the region. High pressure will bring a briefly drier period midweek before greater uncertainty develops late week into the holiday weekend as the front tries to lift back north into the region.

Today through Tuesday Night

Mid and high level cloud debris lingered over the region early this morning with a warm front extending across the southern half of the forecast area. 06Z temperatures were in the 60s.

The atmosphere was worked over substantially from the storms Saturday afternoon with the current ACARS sounding from KIND showing very little instability present above a boundary layer inversion. Convection has recently fired near KCVG in vicinity of the warm front and in tandem with a weak wave aloft. There remains some potential for isolated storms to build back to the W/NW along the front into the eastern part of the forecast area over the next few hours and will keep low precip chances to account. The warm front will continue its northward lift through daybreak and should be north of the forecast area by mid to late morning.

Once the front moves north of the region...any low convective risk will be over for the day as the forecast area settles into the warm sector with a strong mid level cap near 750mb. Diminishing clouds and increasing winds as the pressure gradient tightens will set the stage for a rapid influx of much warmer air into the region for this afternoon. Low level thermals support highs rising into the mid and upper 80s with plenty of sunshine. Deeper subsidence will be advected north into the region tonight which will keep skies mainly clear with warm overnight readings.

Robust convective development will take place late today into this evening over the northern Plains and upper Mississippi Valley shifting east in a weakening state through the night. The remnants of the line will approach the Wabash Valley by midday Monday with the possibility for convection to redevelop along the old boundary Monday afternoon within a warm and unstable airmass over the forecast area. Model soundings show steepening mid level lapse rates with modest instability and sufficient shear that would support the risk for the strongest cells to produce damaging winds and large hail as it moves across the forecast area. Localized flooding will be a threat as well with ample low level moisture present highlighted by PWATs approaching 1.75 inches. High temperatures will be tricky and dependent on timing of the convection. Mid to upper 80s will be possible if storms hold off until later in the afternoon but any earlier arrival will limit temp rises.

Showers may linger Monday night focused over the southern half of the forecast area but the overall trend will be for drier conditions as weak ridging aloft briefly develops across the region. The ridging will be as the eastward expansion of the western trough will flatten the flow aloft Tuesday and finally allow the cold front to make solid eastward progression into the area by late day. A highly unstable airmass across the region will interact with the approaching front and an increasing low level jet to initiate robust convection across the forecast area Tuesday afternoon and evening. Steep mid level lapse rates above 7C/km and dry adiabatic flow through the boundary layer are supportive of a damaging wind risk. Large hail will be a threat with any stronger core owing to the plentiful instability within the hail growth zone. Low level thermals again support temperatures well into the 80s prior to convective development.

Convection will continue Tuesday night as the front sags southeast. Flooding is likely to become a greater concern as the low level jet veers to more of a westerly direction with the potential for cells to backbuild along the boundary overnight.

Wednesday through Saturday

Convection is likely to be ongoing Wednesday morning but will gradually end from northwest to southeast during the day as the front moves into the Tennessee Valley and high pressure builds into the Great Lakes. Model consensus is beginning to hone in on the possibility that the boundary becomes stalled across the Tennessee Valley through Thursday. The high passing to the north should keep mainly dry and cooler conditions across the region but the potential nearby presence of the front to the south will likely warrant maintaining low precip chances across far southern portions of the forecast area. Highs both Wednesday and Thursday will slide back into the upper 60s and low 70s for most of the area.

Lower confidence exists late week into next weekend as the departure of the high pressure to the east and the development of a split flow regime aloft may allow for the aforementioned front to lift back into the region which would introduce the potential for at least scattered convection Friday and continuing into the holiday weekend. The presence of a broad ensemble spread makes employing any detail regarding the timing and coverage of any rainfall challenging at this point. Highs will return to the mid and upper 70s for next weekend.

AVIATION (12Z TAF Issuance)

Issued at 615 AM EDT Sun May 17 2026

Impacts:

- Southerly gusts peaking at 20 to 25kt this afternoon

Discussion:

A warm front draped across the region will shift north of the terminals this morning with S/SW winds becoming gusty by late morning as a tighter pressure gradient develops. May see some flat diurnal cu under a well noted cap this afternoon. Cu and wind gusts will both diminish towards sunset with southerly winds remaining near 10kts overnight. Cannot rule out the potential for marginal LLWS late tonight as the low level jet strengthens over the area. Confidence is too low to include in the forecast at this time but will monitor trends throughout the day.

IND WATCHES/WARNINGS/ADVISORIES

None.