589
FXUS63 KIND 171326
AFDIND

Area Forecast Discussion
National Weather Service Indianapolis IN
926 AM EDT Sat Oct 17 2026

.KEY MESSAGES...

- Widespread frost with localized sub-freezing temperatures
  tonight into Sunday morning. A Freeze Warning has been issued
  for northeastern counties, with a Frost Advisory everywhere
  else.

- Dry conditions expected through the 7 day forecast. Temperatures
  are expected to Sunday onward with warmer then normal
  temperatures next week.

&&

.FORECAST UPDATE...
Issued at 926 AM EDT Sat Oct 17 2026

No major changes needed to the ongoing forecast with conditions
generally evolving as expected. Temperatures have begun to rise out
of the upper 30s after a chilly start to the day. There have been a
few wind gusts up to 15 mph this morning, but as the high pressure
moves overhead, expect wind speeds to continue to fall through the
day. Continued CAA will help to counteract the expected full sun
today with highs topping out in the mid 50s across central Indiana.

No changes currently planned for the overnight headlines, but will
continue to monitor the latest model trends.

&&

.DISCUSSION (Today through Friday)...
Issued at 222 AM EDT Sat Oct 17 2026

Through Sunday Morning:

Most of the forecast period will be rather stagnant as the upper low
associated with yesterday`s trough passage will detach from the flow
and become cutoff over the Eastern Coast. This in combination with a
weak split flow upper jet will keep mid to upper level conditions
fairly similar through the weekend and into next week. While the
bulk of the forecast will remain similar, slight fluctuations in
surface pressure over the next 5-7 days will still lead to slightly
different temperatures and wind speed/direction over the forecast
period.

CAA will be strong through the morning hours, dropping dew points
into the low 30s across northern portions of the area. Even though
skies are clearing, brisk surface winds of 7-10kt will keep the PBL
fairly mixed limiting diurnal cooling and saturation enough to
mitigate frost formation for most areas. Sheltered areas over far NE
central Indiana may see some patchy frost, but this will not be
abundant enough to warrant headlines. Western portions of the
forecast areas may fail to fall below 40 this morning as downstream
cloud cover from Lake Michigan increasing downwelling longwave.

Continued CAA over the next 24 hours will lead to height rises
beneath 850mb and therefor building high pressure through most of
today. The centroid of this surface high is expected to overlap with
the core of the mid level polar airmass late today and tonight of
which will result in our coldest temperatures of the season. Frost
looks definite for most of central Indiana on Sunday morning, but
there is still some uncertainty in below freezing temperatures.
Ensembles are starting to become more aligned on timing of the
surface high passage of which should result in below freezing
temperatures over northern and northeaster central Indiana tomorrow
morning. A Freeze Warning has been issued for these areas, with a
Frost Advisory for the remaining counties.

Remainder of Sunday through Thursday:

The surface high will push off to the east on Sunday, allowing for
weak S/SE flow to develop over the Ohio Valley. This along with
mostly clear skies will lead to a slight rebound in temperatures
with highs on Sunday expected to be in the low 60s. Clear skies and
dry surface conditions will continue large diurnal swings, but there
should be enough of an air mass change to keep temperatures above
freezing Sunday night into Monday morning. Frost potential will
remain high, but headlines will depend if any hard freezes occur
tonight.

Upper level riding will continue to build throughout the beginning
of next week leading to subsidence and dry conditions. Continued S/SW
flow west of the surface high will maintain the steady warming trend
early next week as well. 850mb temperatures are expected to increase
above 10C by Tuesday. This along with dry adiabatic lapse rates in
the PBL should lead to daily temperature above seasonal normals
Monday through Wednesday. Expect large diurnal swings to continue
with lows in the 40s.

&&

.AVIATION (12Z TAF Issuance)...
Issued at 619 AM EDT Sat Oct 17 2026

Impacts:

-None

Discussion:

Northerly winds off of Lake Michigan will continue few to
scattered clouds around 4000ft at KLAF through the morning. This
could reach KHUF, but confidence is too low to include at this
time.

While gusts will not be abundant a few isolated gusts to
20MPH will be possible this morning out of the NNE. This has not
been included in this issuance due to low confidence, but is
something that may be added in later updates.

As high pressure increases this evening, winds will slowly calm,
with a predominant direction out of the ENE at 2-4MPH overnight.


&&

.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.

&&

$$

UPDATE...White
AVIATION...Updike
DISCUSSION...Updike