309
FXUS63 KIND 151352
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
Issued by National Weather Service Louisville KY
952 AM EDT Thu Oct 15 2026

.KEY MESSAGES...

- Showers and thunderstorms today, with isolated severe storms
  capable of damaging winds this afternoon and evening

- Strong post-frontal northwest winds will gust between 25 and 35
  mph on Friday

- Widespread frost and localized freeze conditions are likely
  Saturday night into Sunday morning

&&

.FORECAST UPDATE...
Issued at 933 AM EDT Thu Oct 15 2026

The forecast remains in good shape this morning with no
significant changes needed. Expect mostly quiet weather
conditions through the early afternoon hours before a low pressure
system moves through the region bringing increasing rain and storm
chances late this afternoon into the overnight hours. The isolated
severe weather threat remains in play from mid afternoon into this
evening with more details on the overall threat in the discussion
below. The primary threats are isolated damaging wind gusts and
the potential for a brief tornado.

&&

.DISCUSSION (Today through Wednesday)...
Issued at 131 AM EDT Thu Oct 15 2026

Today through Friday.

As of early this morning, the front that brought rain to central
Indiana is south of the forecast area, but as the next low pressure
system moves in from the Central Plains later this morning, that
front is expected to push back to the north. Ahead of the boundary,
poleward moisture advection characterized by an 850 mb low-level jet
of 40-50 kt will lift surface dew points into the low-to-mid 60s,
creating a short window in the mid to late afternoon hours where
MLCAPE could reach 750 to 1250 J/kg along and south of the I-70
corridor by early afternoon. Kinematic fields are quite robust, with
500 mb mid-level flow around 50-60 kt yielding effective bulk shear
of 45-55 kt. This deep-layer shear will favor organized multi-cell
clusters and linear segments capable of bowing along with an
increasing threat for a few discrete supercells late this afternoon
into the evening.

Low-level 0-1 km storm-relative helicity values of 100-150 m2/s2
will support an isolated brief spin-up along the warm front, but
that threat will be conditional on the front location and extent of
daytime warming. Thus the dominant convective hazard will be
damaging straight-line downdraft winds up to 60 mph via momentum
transport with the tornado threat being secondary. HREF ensemble
members (HRRR, FV3, and ARW) depict initial convective development
across west-central Indiana between 18Z and 20Z, progressing
across the Indianapolis metro area between 21Z and 00Z, and
exiting eastern counties by 02Z-04Z with the potential that this
occurs over 2 rounds through the day QPF will average between
0.50 and 1.00 inches; localized training could produce minor
nuisance ponding in poor drainage areas, but the progressive
motion of the system will mitigate widespread flash flood
concerns.

The cold front will push southeast of the forecast area by 03Z,
bringing an end to heavier precipitation with lingering light rain
through the night. Cold air advection will ensue overnight as 850 mb
temperatures plummet from +12C to near +1C by Friday afternoon. The
tight pressure gradient between the departing surface low over
eastern Canada and a Canadian high building into the Plains will
generate efficient boundary-layer momentum transfer. Diurnal mixing
into the 850-800 mb layer will tap into 35-40 kt ambient flow,
supporting sustained northwest winds of 18-25 mph with frequent
gusts of 25-35 mph Friday afternoon. Cyclonic flow and steep low-
level lapse rates will foster an extensive stratocumulus deck,
particularly across the northern two-thirds of the CWA. Highs on
Friday will remain suppressed, ranging from the upper 50s north to
the lower 60s south. Winds Friday night should keep frost
formation limited even as temperatures drop into the mid to upper
30s, but sheltered areas could see some frost ahead of a
widespread frost Saturday night.

Saturday Through Wednesday.

A broad longwave trough will anchor across the eastern CONUS on
Saturday as a strong  surface anticyclone shifts from the Upper
Mississippi Valley southeastward across the Ohio Valley through
Sunday. The core of the cold pool will sit overhead Saturday,
keeping 850 mb temperatures around 0C to +2C. Despite clearing skies
and subsidence, daytime highs on Saturday will struggle to reach out
of the mid 50s, 10-15 degrees below normal.

Saturday night into Sunday morning represents the primary frost and
low-end freeze window of the period. The surface high center will
settle directly over central Indiana by 09Z Sunday, decoupling the
boundary layer and yielding calm winds, clear skies, and a very dry
ambient air mass with dew points in the upper 20s to low 30s. Strong
radiational cooling will cause overnight minimum temperatures to
drop into the lower to mid-30s across the entire forecast area, with
rural drainage basins and traditional cold spots likely dropping near
freezing. Widespread frost is expected across central Indiana, and
freeze conditions are probable in sheltered rural areas. Frost and
freeze headlines will likely be required as confidence remains high
across deterministic GFS, ECMWF, and their respective ensemble
suites.

The anticyclone will drift eastward toward the Mid-Atlantic on
Sunday, allowing insolation to rebound highs into the upper 50s and
lower 60s. Lows Sunday night will remain cool, in the upper 30s to
lower 40s, with patchy frost confined to far eastern rural valleys
before low-level winds back to the south.

For Monday through Wednesday, the synoptic pattern transitions as
upper-level ridging builds over the eastern states and a deep trough
carves out over the western CONUS. Steady south-southwesterly return
flow will drive a significant warm air advection regime across the
Ohio Valley. 850 mb temperatures will moderate to +10C to +13C,
pushing daytime highs into the lower 70s on Monday and mid-70s on
Tuesday. Overnight lows will moderate into the upper 40s to mid-50s.

Medium-range guidance indicates an ejecting northern-stream
shortwave trough will drag an associated surface cold front toward
the Lower Great Lakes and Ohio Valley Tuesday night into Wednesday.
Moisture convergence ahead of this boundary will raise precipitable
water values back above 1.25 inches, supporting chance to likely
PoPs for rain showers and isolated embedded thunderstorms late
Tuesday night through Wednesday afternoon. Displaced upper-level
dynamic support and marginal instability currently suggest a low
probability of severe weather with this mid-week frontal passage.
Temperatures on Wednesday will run in the upper 60s to lower 70s
ahead of the front.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 552 AM EDT Thu Oct 15 2026

Impacts:

- MVFR to IFR cigs are expected for much of this TAF period
- Showers and storms expected this afternoon, confidence highest at
  HUF and BMG
- Additional showers tonight, coverage decreasing after 06Z
- Wind shifts through the period
- Wind gusts 15-20kt tonight, up to 25kt after 15Z Friday

Discussion:

MVFR cigs are expected for much of the day with periods of VFR ahead
of the next round of rain during the afternoon hours. Confidence is
highest in the 19Z to 00Z timeframe towards BMG and HUF where both
brief gusty winds and lightning are possible. The lightning
potential looks lower for LAF and IND with thunder chances
decreasing after 02Z. Vsbys should remain VFR outside of stronger
showers and storms. Easterly winds this morning will become
southerly this afternoon, and westerly during the evening before
finally turning to the northwest during the overnight into Friday.
Gusts are expected to start late this evening outside of convection
and continue through the remainder of the TAF period with peak gusts
up to 25kt after 15Z Friday.


&&

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

$$

UPDATE...Melo
AVIATION...White
DISCUSSION...White