484
FXUS63 KIWX 300935
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
535 AM EDT Tue Sep 30 2025

.KEY MESSAGES...

- Much above normal temperatures to continue today with highs
  in the low to mid 80s.

- Cooling slightly for Wednesday and Thursday but high
  temperatures are expected back into the lower to middle 80s
  for Friday into the weekend.

- Dry weather continues through the remainder of the week.

&&

.DISCUSSION...
Issued at 234 AM EDT Tue Sep 30 2025

Mid level ridging overhead offsets uplift southeast of the US and
this suppression of rain-producing systems as a result of the
ridging and antecedent dry air continues into early next week.

Riding over the top of this stalled ridging is a surface high
pressure system that ends up in southeast Canada and the
northeastern US today and Wednesday. The main change that will
result from a backdoor cold front that arrives Wednesday and
Thursday will be dry air as dew points in the 40s will become more
possible and widespread, especially on Thursday. Meanwhile,
temperatures will slowly stair step down from our mid to upper 80
degree highs, experienced Saturday through Monday, to more 70 degree
highs Wednesday and Thursday. Widespread 30 percent MinRH values and
varying amounts of 20 percent MinRH values will be present from
Tuesday through Thursday. The good thing is a majority of our winds
are expected to be light enough to restrict the spread of grass
fires. The one exception might be Wednesday when 15 to 25 mph gusts
are possible mainly along and north of US-30. Now, sometimes with
these fronts, we end up with sprinkles as low to mid level moisture
is able to fall and evaporates in a dry boundary layer. It appears
that, while some clouds will be around, not enough moisture will be
around to create rainfall.

A trough resides on the west coast of the CONUS and normally this
would be enough to get Gulf moisture and get a rain chance into the
area. However, the mid level ridging, antecedent dry air and the
tendency for the vorticity to shear out and weaken as it traverses
northward to west of the area will allow the rain chances to
evaporate before they arrive here. Finally, better Gulf moisture
arrives on the backside of a ridge in the southeastern US between
Monday and Tuesday of next week in advance of a cold front. This
pattern is usually conducive to rain, but we`ll need to see if the
60 degree dew points can, in fact, make up this way and overcome the
antecedent dry air.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 535 AM EDT Tue Sep 30 2025

No changes for the 12Z TAFs. Quiet, dry weather persists
with light and variable winds and VFR ceilings. Patchy ground
fog has developed this morning away from the terminals, with
visibilities generally around 4 to 7 miles but as low as 1 mile
in rural, low lying spots. I have continued to leave fog out of
the TAFs as it should not be operationally significant to the
terminals. Winds will be out of the northeast by the early
afternoon between 5 to 10 kts.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Johnson