textproduct: Indianapolis

KEY MESSAGES

- Gusty winds up to 35 mph this afternoon

- Scattered showers and thunderstorms tonight and again on Wednesday

- A few strong storms cannot be ruled out with a low threat for localized flooding, primarily Wednesday afternoon

- Rain chances again Friday into Saturday and early next week

- Above normal temperatures through early next week

MESOSCALE UPDATE

Issued at 847 PM EDT Tue Apr 21 2026

Elevated convection rooted between 800-700mb will continue to progress E-SE around 35 kts across northern portions of central Indiana through midnight. This activity formed ahead of a weak shortwave trough and modest deep moisture convergence and in a region of steep mid level lapse rates (7.5 to 8.5 C/KM).

Recent observed sounding from ILX shows a nice inverted V sounding beneath marginal instability (600-700 j/kg) with 700 j/kg of DCAPE. Activity in northern Indiana has shown no signs of producing strong winds, but surface analysis trends the last 2 hrs show a cold pool/pressure rise max centered over N-NE portions of IN into far NW OH. As a result, TS activity has been developing a little more of a southward component to its vector. Activity is going to be gradually moving into a progressively drier environment with decreasing buoyancy owing to cooling boundary layer. Meanwhile, an increasing W- SW low level jet over 40 kts centered about 1.5 km AGL is noted on the recent KVWX VWP. This low level jet is forecast to intensify and develop across central Indiana through 03Z. On the southern fringes of the modest instability there may exist a narrow corridor both spatially and temporally for a strong/isolated damaging wind gust or two through 04Z before thermodynamics/low level lapse rates become prohibitively small to warrant any additional wind potential the remainder of the night. The threat for hail will continue to diminish as the corridor of steepest mid level lapse rates outruns the convection with the KILX 00Z sounding showing around 7.5 C/KM. Thus only small hail is possible in the strongest precip cores.

DISCUSSION (This evening through Tuesday)

Issued at 307 PM EDT Tue Apr 21 2026

Strong southwesterly flow has quickly warmed temperatures into the 70s this afternoon. Diurnal mixing combined with a tight MSLP gradient is promoting strong wind gusts up to 35 mph. A weak cold front associated with a low pressure system will approach the area later this evening into the overnight hours. Modest forcing and destabilization along or just ahead of the boundary supports the potential for scattered showers and thunderstorms. Severe weather is unlikely due to diurnal stabilization into the overnight hours, but strong wind gusts and small hail are possible in any loosely organized storms.

The aforementioned front will likely stall near northern Indiana tonight. This along with any remnant boundaries from convection later today may support additional thunderstorm development on Wednesday. Confidence in thunderstorm coverage for Wednesday remains low due to forcing primarily being driven by mesoscale features. Models also depict varying solutions, but generally show the greatest chance for convection over the northern half of central IN during the afternoon.

There does appear to be a non-zero threat for a stray strong to severe thunderstorm Wednesday afternoon. Shallow inverted V sounding profiles with mid-level dry air suggest the potential for strong downbursts. These would likely be sub-severe for the most part, but can't rule out an isolated damaging wind gust. Small hail is also possible given daytime heating and moisture advection will promote modest to moderate instability. Weak deep-layer shear will largely limit the threat for severe hail, but cannot completely rule it out either in any loosely organized storms. Localized flooding appears possible due to slow storm motions and some potential for training to occur.

Thursday through early next week...

Upper ridging centered over the region should provide quiet weather on Thursday while the aforementioned stalled diffuse front begins to lift northward as a warm front. Deep upper troughing across western portions of the United States will then eject multiple impulses towards the region late this week through early next week. The greatest precipitation chances are still on Friday when a low pressure system and associated cold front push into the area. Severe weather is not expected at this time due to limited instability and deep layer wind shear, but a few strong storms cannot be ruled out. Rain chances range from 60 to 80 percent.

The cold front may stall near central Indiana on Saturday keeping low chances for rain or storms in the forecast. The primary forcing would likely be driven by the diffuse front so confidence is limited as some guidance has the boundary south of central Indiana on Saturday while others keep it near south-central Indiana. The greatest precipitation chances are across the south and east, but POPs will likely need to be refined once guidance becomes better aligned on the placement of the front. Sunday should be dry with most guidance depicting weak surface high pressure building in behind the departing front.

Slightly higher rain chances return towards early next week when long range guidance suggest another developing low pressure system could move towards the region. Specific details remain highly uncertain as there is a large spread in model solutions, but there does appear to be a low chance for severe weather. This setup will continue to be monitored closely. Temperatures are expected to remain above normal during the period.

AVIATION (00Z TAF Issuance)

Issued at 746 PM EDT Tue Apr 21 2026

Impacts:

- Scattered showers with chances of TS developing mid evening lasting into early Wednesday. - LLWS late this evening through Wednesday early morning. - MVFR ceilings developing Wednesday morning. - Chances of thunderstorms Wednesday afternoon.

Discussion:

Wind gusts have peaked at all the terminals earlier this afternoon and will continue to diminish through 03Z. However, winds aloft will increase during this same time period leading to the development of LLWS AOB 020 at all terminals except at KLAF. The LLWS is expected to weaken later tonight as the winds aloft diminish to under 40 kts. Surface winds will remain generally W-SW under 15 kts through Wednesday.

A weak upper disturbance will continue to support showers with isolated to widely scattered TS overnight. This activity will be near KLAF through 03Z then eventually near KIND after the cargo ops tonight. However, as the activity moves further south, the threat for TS diminishes and have removed any TS chance wording for KHUF/KBMG with further weakening trends towards daybreak with loss of forcing.

In the wake of the convection, MVFR ceilings are expected to develop at all terminals except KBMG and last through early afternoon. With gradual clearing, sufficient instability may develop for scattered TS to form after 20Z. For now went with a broad brush PROB30 for TS at all terminals through 00Z.

IND WATCHES/WARNINGS/ADVISORIES

None.