725
FXUS63 KIND 081006
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
606 AM EDT Thu Oct 8 2026

.KEY MESSAGES...

- Slightly elevated fire weather danger today and Friday due to low
  relative humidity and dry ground conditions

- Widespread rain and cooler temperatures expected Saturday night
  into Sunday from tropical moisture remnants

&&

.DISCUSSION (Today through Wednesday)...
Issued at 134 AM EDT Thu Oct 8 2026

Today Through Friday.

An upper-level shortwave trough tracking across the Upper Great
Lakes has pushed dry surface boundary south across central Indiana
over the last few hours with the wind direction now generally
westerly to northwesterly across the forecast area. Diurnal heating
will deepen the boundary layer to around 4kft, but weaker winds at
the top of the boundary layer will keep wind gusts more towards
15mph this afternoon and evening. Very dry mid-level air entraining
into the boundary layer will cause minimum relative humidity values
to drop into the 20 to 30 percent range during the afternoon.
Combined with 10-hour fuel moisture values near 10 to 12 percent
from antecedent dry conditions, slightly elevated fire weather
danger is expected but the lighter winds will limit any higher-end
impacts. High temperatures will top out in the upper 70s. High
pressure building in behind the trough tonight will yield clear
skies and light winds, favoring strong radiational cooling with
overnight lows dropping into the upper 40s to low 50s.

On Friday, surface high pressure shifts eastward across the eastern
Great Lakes, establishing a light easterly to southeasterly low-
level flow regime across the Ohio Valley. Model soundings from the
GFS and ECMWF show persistent subsidence aloft keeping column
moisture low, with PWATs under 0.60 inches. Mostly clear skies will
allow afternoon highs to reach the mid 70s. Southeasterly return
flow increases slightly Friday night as the surface high exits
toward the Mid-Atlantic. Increasing upper-level cloudiness ahead of
the approaching tropical system will keep Friday night lows slightly
warmer, ranging from the upper 40s in the east to lower 50s in the
west.

Saturday Through Wednesday.

Primary focus for the long term period centers on the interaction
between a Central Plains mid-level trough and tropical moisture
associated with the remnants of Hurricane Isaias. Deterministic
and ensemble guidance, including the GFS, ECMWF, GEFS, and EPS,
demonstrate solid consensus in the remnants traveling north into
the Ohio Valley bringing abundant tropical moisture both near the
surface and aloft. High temperatures Saturday will reach the mid
70s under thickening cloud cover.

Precipitation will develop rapidly late Saturday evening and peak
overnight into Sunday morning as strong isentropic lift is maximized
beneath the right-rear quadrant of an accelerating Great Lakes jet
streak. Dynamic cooling and widespread rainfall will keep Sunday
high temperatures suppressed in the upper 60s, while elevated
surface dewpoints hold Sunday night lows in the upper 50s.
Ensemble probabilities for 24-hour rainfall exceeding 0.75 inches
exceed 70 percent across central and southern Indiana, supporting
the potential for a 1.0 to 1.5 inch rainfall event if the track
remains near to what the NHC is currently forecasting. There are
some signs that the track may shift a bit to the southeast which
will keep the axis of heavier rain focused closer to the Ohio
River, but we continue to monitor the trends.

Rain will taper off from west to east Sunday evening as the tropical
moisture core shifts toward the Mid-Atlantic and a mid-level dry
slot moves in behind the exiting trough axis. Transient mid-level
ridging and surface high pressure build in on Monday, allowing warm
southwesterly flow to push high temperatures back into the upper 70s
under mostly sunny skies.

By Tuesday and Wednesday, a deeper northern stream trough is
forecast to amplify over the Great Lakes region, sweeping a strong
cold front across central Indiana Tuesday. Cold air advection behind
the boundary will bring temperatures closer to normal by Wednesday.
Confidence on any precipitation with this frontal passage remains
fairly low with only modest forcing with the system.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 605 AM EDT Thu Oct 8 2026

Impacts:

-Northwesterly gusts up to 20kt this afternoon

Discussion:

VFR conditions expected through the TAF period with clear skies and
northwesterly winds. There will be a few gusts up to 20kt at IND and
LAF this afternoon, mainly from 18Z to 00Z before winds drop to near
calm after sunset.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

AVIATION...White
DISCUSSION...White