955
FXUS63 KIND 171725
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
125 PM EDT Sat Oct 17 2026

.KEY MESSAGES...

- Widespread frost and localized freezing temperatures tonight
- A Freeze Warning is in effect for much of eastern and portions of
  central Indiana, Frost Advisory elsewhere
- Dry and quiet weather through the next 7 days with temperatures
  rebounding well above normal by midweek

&&

.DISCUSSION (This evening through Saturday)...
Issued at 124 PM EDT Sat Oct 17 2026

Tonight Through Sunday Night.

Surface high pressure centered across the Mid-Mississippi Valley
this afternoon will drift east across Indiana tonight, establishing
optimal conditions for boundary layer decoupling. Strong synoptic
subsidence in the wake of the exiting upper trough will maintain
clear skies. Light and variable to calm winds are anticipated across
the entire forecast area after 02Z with temperatures rapidly
dropping out of the mid 50s and into the low 40s by late this
evening.

The primary forecast challenge continues to center on overnight
minimum temperatures and associated frost/freeze headlines. The
aforementioned efficient radiational cooling will allow for
temperatures to drop into the low to mid 30s across all of central
Indiana with uncertainty remaining as to where the best chances for
sub-freezing temperatures will be. As of early this afternoon, dew
points remain generally at or above 32 but expect at least some
additional drops as northerly to northeasterly flow continues. NBM
continues to run on the cooler side of most hi-res guidance with the
Canadian and its associated ensemble pushing down the mean, but with
such efficient radiational cooling expected the Canadian may be
closer to reality than the HRRR/NAM. The WRF-ARW which similarly
handles efficient radiational cooling shows temperatures near to
below freezing for much of central Indiana. Thus, generally expect
all areas to see a widespread frost with more rural areas to see
temperatures at or below freezing. Urban areas will end up a degree
or two above, but with the uncertainty as to where the freeze will
occur, not planning on adjusting the headlines at this time.

By Sunday, the surface anticyclone center slips eastward into the
upper Ohio Valley and central Appalachians. Low-level flow will back
to the south-southwest at 5 to 10 mph by afternoon. Model soundings
show a dry atmospheric column with precipitable water values under
0.35 inches, supporting abundant sunshine. Boundary layer mixing up
to approximately 900mb where temperatures recover to 6C to 8C will
allow afternoon maximum temperatures to rebound into the lower to
mid 60s. For Sunday night, modest south-southwesterly return flow
will keep the boundary layer slightly mixed, holding minimum
temperatures in the upper 30s to lower 40s and precluding
significant frost concerns outside of isolated sheltered depressions.

Monday Through Saturday.

The medium-range period will be characterized by a stagnant, highly
amplified synoptic regime featuring ridging over the eastern third
of the CONUS and a deep closed trough digging into the Western
States. With surface high pressure anchored off the Mid-Atlantic
coast, persistent low-level southwesterly flow will advect a much
milder continental airmass northward. 850mb temperatures are
forecast to warm from 9C on Monday to near 13C to 15C by Wednesday
and Thursday. Under mostly sunny to partly cloudy skies, daytime
highs will peak in the upper 60s to lower 70s on Monday, reaching
the mid to upper 70s Tuesday through Thursday, which is roughly 10
to 15 degrees above seasonal normals. Overnight lows will
concurrently moderate into the 40s Monday night and the lower to mid
50s for the remainder of the week.

Dry weather will dominate the regional sensible weather through at
least Thursday night due to deep-layer subsidence, strong capping
around 800mb, and the diversion of synoptic moisture plumes well
northwest into the Upper Midwest. Toward the Friday and Saturday
timeframe, deterministic solutions diverge regarding the ejection
speed of the western trough into the northern Plains. There are some
signs that there may be a decaying frontal boundary nearing the area
by late Friday but confidence is low in any precipitation chances
with the strong ridging in place ahead of time.

&&

.AVIATION (18Z TAF Issuance)...
Issued at 124 PM EDT Sat Oct 17 2026

Impacts:

-None

Discussion:

VFR conditions through the TAF period with clear skies expected as
high pressure moves overhead. Northeasterly winds of 5-10kt will
gradually drop to calm after 00Z with winds then gradually becoming
southerly again after 12Z Sunday.

&&

.IND WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from 2 AM to 9 AM EDT Sunday for INZ021-028-029-
035-043>045-047-051>055-060>064-067>072.

Freeze Warning from 2 AM to 9 AM EDT Sunday for INZ030-031-
036>042-046-048-049-056-057-065.

&&

$$

AVIATION...White
DISCUSSION...White