textproduct: Indianapolis

KEY MESSAGES

- Showers and a few t-storms tonight, gusty winds possible

- Dry and seasonable Wednesday through Friday

- Warming trend this weekend and into next week, above normal temperatures likely

FORECAST UPDATE

Issued at 1009 AM EDT Tue May 12 2026

The forecast for today looks on track as winds turn southerly and increasing warm air advection ahead of an approaching front allows for surface temperatures to warm into the mid to upper 70s. Main focus for this update will be on the thunderstorm and severe potential later this evening and overnight tonight. Current satellite and ACARs soundings depict a very dry environment currently; however upstream observations show increasing moisture advection ahead of the front...enough to support thunderstorm activity as seen in Iowa this morning. Will be watching how afternoon mixing into a dry layer aloft slows the moisture advection this afternoon, however CAMs does depict deeper moistening through the column near and after sunset as mixing wanes and moisture advection increases just ahead of the front. Latest CAMs show an arrival time of storms around 10PM in Northwestern portions of Central Indiana; however if storms to the northwest develop a cold pool, they may arrive earlier in the evening. If an earlier arrival time occurs when the atmosphere is a bit more unstable, the severe potential may increase. Due to this being an overnight threat, expect the severe/thunder potential to decrease through the night as the line of showers and storms tracks southeast. With such dry lower levels, thinking the largest threat will be strong winds with any shower or thunderstorm. The entire atmosphere looks only marginal to support any type of severe weather due to marginal lapse rates, moisture, and instability, but the threat is still non zero despite not being overly concerned. Greatest threat for a thunderstorm looks to be along and north of I-70, especially in NW Indiana after sunset. Rainfall amounts should be fairly light overall, despite brief periods of heavier rainfall rates. Thinking drier air ahead of the storms will limit the overall heavy rain threat, especially as showers and storms weaken through the night.

DISCUSSION (Today through Monday)

Issued at 130 AM EDT Tue May 12 2026

Overview.

Surface high pressure currently centered over the Great Lakes continues to dominate the weather pattern across central Indiana. This feature is providing clear skies, light winds, and comfortable, near-normal temperatures. Atmospheric moisture profiles remain quite dry, ensuring a quiet night ahead with excellent radiational cooling. Rain chances then arrive tonight as a low-pressure disturbance over the northern Plains tracks eastward. Dry and quiet weather is then expected through the early weekend when the next upper level wave brings low rain chances.

Tuesday through Wednesday.

The primary focus for impactful weather arrives Tuesday night as a cold front sweeps through the region. High-resolution forecast models indicate that mid and high-level cloud cover will thicken during the afternoon and evening hours today ahead of the approaching boundary. Widespread rain showers and a few embedded thunderstorms are expected to overspread central Indiana tonight, persisting into the early morning hours of Wednesday.

Meteorologically, moisture transport will improve as low-level wind profiles shift to the southwest ahead of the front late today. Any severe weather potential is heavily constrained by a lack of atmospheric instability. Despite the lack of robust instability, strong winds aloft within the lower kilometers of the atmosphere could be efficiently transferred to the surface. Consequently, the main hazard with these showers will be sporadic, sub-severe wind gusts, along with brief heavy downpours and lightning.

Precipitation will taper off rapidly from west to east on Wednesday morning as the cold front departs. Strongly building high pressure behind the front will clear out remaining cloud cover by Wednesday afternoon. Cooler, drier air filtering into the region will keep daytime temperatures near or slightly below seasonal averages, with highs generally resting in the upper 60s to lower 70s.

Thursday through Monday.

A prolonged period of tranquil and increasingly warm weather is expected late this week and through the early weekend. Surface high pressure will firmly establish itself over the Ohio Valley on Thursday and Friday, promoting mostly sunny skies, light winds, and highly favorable outdoor conditions.

By the weekend, a significant shift in the upper-level atmospheric pattern will take place. Both global deterministic models and ensemble clusters exhibit strong consensus regarding the amplification of a prominent upper-level ridge of high pressure across the eastern half of the US. Strong warm air advection on the backside of the departing surface high will draw an unseasonably warm airmass into Indiana. High temperatures are projected to climb from the low 70s on Friday into the lower to mid- 80s by Saturday through Monday, which is well above normal for the middle of May.

While a few individual model simulations attempt to introduce isolated showers over the weekend via weak, localized atmospheric disturbances, ensemble means suggest that the capping influence and sinking air associated with the building upper-level ridge will suppress most convective development. Furthermore, low-level moisture return looks quite subtle, which will limit the instability necessary for widespread storms. Therefore, the forecast maintains only 20-30 percent chances for rain.

AVIATION (12Z TAF Issuance)

Issued at 545 AM EDT Tue May 12 2026

Impacts:

- Wind shift from north to southwest this morning - MVFR to briefly IFR vsbys due to SHRA after 03Z - LLWS after 03Z - Southwesterly gusts up to 25kts after 17Z

Discussion:

VFR conditions expected through much of the TAF period. Cigs will gradually fall during the day today as upper level moisture begins to increase ahead of likely rainfall late this evening into tonight. Earliest chances for rainfall look to be around 01Z at LAF with chances increasing through 04Z. Brief MVFR to IFR vsbys will be possible at times with cigs expected to remain VFR. There may also be a few rumbles of thunder, but confidence is too low to mention in the TAF at this time. In addition to the rain, a strengthening LLJ will introduce LLWS from 03Z onwards. Rain chances then look to end towards 09Z with cigs around 050. Northeasterly winds will gradually become more easterly then southwesterly during the morning hours with a few gusts up to 25kts after 17Z.

IND WATCHES/WARNINGS/ADVISORIES

None.