textproduct: Indianapolis

KEY MESSAGES

- Low relative humidity this afternoon will create minor fire weather concerns, though light winds will keep risks limited

- Rain likely Saturday night into Sunday due to tropical remnants, total amounts trending down

DISCUSSION (Today through Thursday)

Issued at 130 AM EDT Fri Oct 9 2026

Today Through Saturday.

Surface high pressure centered across the Upper Midwest will build southeastward into the Great Lakes region on Friday. Large-scale subsidence within the building ridge axis will maintain mostly clear skies. A weak wave aloft will bring some saturation towards 15kft, especially across the northern counties, so will bump up sky cover a bit, but otherwise expect only minimal cloud cover. The boundary layer isn't expected to be quite as deep today, but very dry air within it will allow for another day of crashing dew points during the afternoon hours with the potential for pockets of sub 20 percent RH. With the shallower boundary layer, wind gusts will be less frequent compared to the last few days.

On Saturday, the surface high will shift toward the Mid-Atlantic coast, returning southerly low-level flow to the Ohio Valley. Model soundings from the GFS and ECMWF display a gradual increase in upper- level moisture, with cirrus filtering into the region ahead of an advancing Central Plains trough and the eventual tropical remnants. Warm air advection in the 925mb to 850mb layer will boost afternoon high temperatures into the mid 70s to around 80. Deep-layer dry air will remain intact through much of the daytime, keeping PoPs below 10% through Saturday afternoon. Low-level moisture return will begin to ramp up Saturday night, with surface dewpoints climbing into the upper 50s as the pressure gradient tightens ahead of the approaching trough and remnants.

Sunday Through Thursday.

Model guidance over the past 24 hours has trended toward a slightly faster and more southeasterly track regarding the tropical remnants of Hurricane Isaias as the system interacts with a mid-level shortwave crossing the Midwest. Recent runs of the GFS, ECMWF, and their respective ensemble means show the primary moisture plume and associated moisture advection shifting east into the Upper Ohio Valley and Appalachian region. Consequently, lower-level deformation and dynamic forcing over central Indiana appear weaker, resulting in lower total rainfall projections. Trough passage and a mid-level dry slot will clear precipitation out from west to east by Sunday afternoon. Highs on Sunday will range from the upper 60s to lower 70s under lingering cloud cover.

Brief mid-level ridging and surface high pressure will establish dry and warm conditions Monday and Tuesday. Return southwesterly flow will push high temperatures into the upper 70s to lower 80s on Monday, falling back into the mid 70s on Tuesday ahead of an approaching northern stream trough.

A more significant synoptic pattern transition is indicated in medium-range ensemble guidance for Wednesday into Thursday. Guidance depicts a deep longwave trough amplifying over the Central CONUS, driving a strong surface cyclone through the Upper Midwest and sweeping a robust cold front across the Ohio Valley. Strong upper- level jet dynamics and deep thermal contrast will support robust dynamic forcing, introducing increasing rain chances late Wednesday into Thursday. Ensemble ensemble cluster analysis indicates strong cold air advection behind the frontal boundary.

AVIATION (06Z TAF Issuance)

Issued at 130 AM EDT Fri Oct 9 2026

Impacts:

-None

Discussion:

VFR conditions expected through the TAF period with gradually increasing cloud cover during the daytime hours today as high cirrus moves in from the northwest. There could be a few showers near LAF but with the dry surface air, expect any rain to remain northwest of the terminal. Northerly winds will become southwesterly by mid- morning with speeds generally at or below 10kt.

IND WATCHES/WARNINGS/ADVISORIES

None.