textproduct: Indianapolis

KEY MESSAGES

- Cooler and rainy today with isolated thunderstorms possible.

- Heavy rain could result in localized flooding of low lying and agricultural areas.

- Largely below normal temperatures this upcoming week, with multiple chances for more rain on Friday Night and again on Sunday.

DISCUSSION (This evening through Tuesday)

Issued at 311 PM EDT Tue May 5 2026

Steady rain has overspread much of central Indiana as of 2pm, though a break in the rain is taking shape towards the Illinois state line. This should gradually fill in as broad forcing aloft arrives from the west. Guidance is in excellent agreement showing widespread rain through the evening and into the overnight. Additionally, some weak instability may creep far enough north to allow for embedded convection capable of thunder. Overall, instability is only a couple hundred J/Kg in the most aggressive solutions...so we will keep the mention of thunder to a minimum.

Model soundings indicate a fairly deep warm cloud layer (around 10000 feet) with a mostly saturated column. As such, warm rain processes with abundant moisture (PWATS around 1.25 inches) should allow for efficient rainfall production today. Any embedded convective element could allow for rather heavy rainfall rates despite meager radar appearance. Therefore localized flooding is our primary hazard today. Flash flooding is less of a concern, as rainfall rates shouldn't be high enough for that. Slower inundation of low-lying areas and roadways is more probable. Most guidance shows between 1-2 inches of additional rainfall through tonight, with the highest amounts along and south of I-70.

Tonight

Additionally, winds have turned northerly behind a cold front that is moving southward this afternoon. Temperatures have dropped around 5 degrees with the frontal passage and a slow drop is expected into tonight. Lows in the 40s are likely for much of the region by sunrise Wednesday. Cloud cover will take longer to clear out than the rain which should help limit radiational cooling. However, should clearing occur then patchy fog cannot be ruled out.

Wednesday

Partly to mostly cloudy skies prevail on Wednesday within the post- frontal environment. Temperatures are expected to be cool, roughly 10-15 degrees below average for this time of the year (average highs in the low 70s). Surface high pressure building in will keep winds rather light.

Thursday

Surface high pressure is firmly established by Wednesday night, and ideal radiative cooling conditions look to be present. Clear skies, light winds, and a subsident atmosphere should promote temperatures into the upper 30s by sunrise Thursday. Patchy frost and fog may be possible, mainly in rural areas where cooling potential is greatest. Light winds and sunny skies will allow for a steep diurnal curve, with temperatures rebounding nicely to near 60s by the afternoon.

High pressure begins departing to the east Thursday night, allowing for southwesterly flow to develop. Winds at the surface remain light, however, under a stable boundary layer. As such, another night with good radiative cooling potential is likely Thursday night. Lows in the low 40s appear likely.

Friday onward

Southwesterly flow intensifies on Friday with warmer weather expected. Highs near 70 return for much of the area. Though low- level flow is out of the southwest, broad northwesterly upper-level flow remains in place. Ensemble guidance shows a shortwave trough diving southeastward late Friday. With little surface reflection, mass response is limited. Nevertheless, enough moisture should lift northward to allow for scattered showers and thunderstorms. Model soundings do not show a lot of instability, a couple hundred J/Kg at most, but enough for the mention of isolated thunder.

Broad troughing persists into the weekend and potential early next week. As such, near to below average temperatures are favored. Ensemble guidance is hinting at a return to a warmer weather pattern around mid-month, though the signal isn't very clear at the moment.

AVIATION (18Z TAF Issuance)

Issued at 158 PM EDT Tue May 5 2026

Impacts:

- MVFR conditions with rain today. An isolated thunderstorm possible. - IFR ceilings at times through this evening.

Discussion:

Rain has overspread central Indiana and is redeveloping upstream across Illinois as well. As such, rain is expected to continue at all the TAF sites this afternoon into the evening hours. As the lower atmospheric moisture increases, IFR ceilings are likely to develop this afternoon continuing into the evening. Rain ends around 06z with gradual improvement in sky cover thereafter. There is a low probability of thunder (under 20 percent) but will not be mentioned in the TAFs for now.

Winds are becoming northerly as a cold front slowly drops southward across Indiana. Speeds have been under 10kt so far, but a period of 10-13kt winds is possible for a few hours this evening. Winds diminish once again overnight into the day Wednesday.

VFR conditions return Wednesday morning although SCT to BKN skies persist through the day.

IND WATCHES/WARNINGS/ADVISORIES

None.