217
FXUS63 KIWX 041829
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
229 PM EDT Sat Oct 4 2025

.KEY MESSAGES...

- Warm and dry conditions persist with highs in the mid to upper 80s
  once again on Sunday.

- The combination of dry conditions and gusty winds could lead to
  an elevated risk for field fires this weekend, particularly
  for Sunday.

- Rain is expected Monday night into Tuesday, with much cooler
  conditions for the middle and end of next week.

&&

.DISCUSSION...
Issued at 228 PM EDT Sat Oct 4 2025

Unseasonably warm conditions will continue through the remainder of
the weekend as pronounced mid/upper level ridging maintains its
influence.

A diurnal cu field will continue to mature through late afternoon,
with some question once again as to potential of an isolated
shower. Some weakness in mid level heights was noted yesterday
in comparison to today, and better mixed low levels today should
also gradually diminish sfc based instability over next few
hours. Weak mid level subsidence has also had a long residence
time across the area over past few days with persistent weak
subsidence inversion, so would suspect coverage of any showers
will remain isolated enough to keep PoPs below gridded forecast
mention. By late afternoon, any isolated shower/sprinkle
potential should be limited to far northern Indiana/southern
Lower Michigan as warmer mid level temps build in from the south
with better sfc based CIN. Quiet conditions expected for
tonight, with mins tonight similar to that of yesterday morning
given weak low level thermal advection over the past 18 hours.

The fire weather risk for Sunday continues to be the primary
forecast concern for the short term. A lead upper level short wave
will race across Upper Midwest on Sunday with deepening sfc
reflection of this wave reaching western Ontario by Sunday evening.
Deepening of this system will augment low level height gradient
for Sunday. Guidance still suggests a deep boundary layer
Sunday afternoon with boundary layer averaged winds of 15 to 20
knots, maximizing across northwest half of the area. Some very
weak low level CAA working in from the south may result in max
temps slightly cooler than yesterday. This southerly flow will
also allow some weak low level dry air advection to work in from
the lower Ohio Rvr Valley with dew points expected to mix out
into the lower 50s Sunday afternoon (possibly a bit lower for
localized areas). The above should result in minimum RHs from 25
to 35 percent, but would not be surprised if localized areas
drop to around 20 percent (particularly for areas in higher
drought categories across NE IN/NW OH). One factor that could
alleviate higher end fire weather concerns for Sunday is that
the strongest sfc wind gusts to 20 to 25 mph are expected across
the northwest, and not in areas experiencing the most
significant drought conditions.

For late Sunday night into Monday, upper ridge will be dampened by
the departing Ontario short wave, but then attention will turn
to a larger scale negative upper height anomaly digging across
south central Canada which will allow cold frontal boundary to
sink toward southern Great Lakes Monday night into Tuesday. Best
pre-frontal moisture transport still looks to affect areas from
southern Indiana into central Ohio, while low level fgen
forcing remains divorced from this deeper moisture through
Monday evening. The wildcard in this forecast will be the
strength of mid/upper level wave shifting east from the northern
Rockies later Tuesday into early Wednesday. The GFS
deterministic remains an outlier in terms of strength of this
wave and resultant uptick in fgen forcing. Still feel that
EPS/GEFS idea of greatest potential of greater than 0.50" inches
of rain would be generally along/south of US 24 corridor where
best moisture transport exists, but much of precip distribution
will depend on how strong renewed fgen response is on Tuesday
with the approaching mid level trough. Low chance thunder
mention maintained despite poor mid level lapse rates and
marginal instability with guidance continuing to indicate decent
upper dynamics in right entrance region of jet streak.

Much cooler conditions for the middle of next week will moderate to
seasonable levels toward the end of this period. Additional
precip late next work week will be kept as slight chance with
marginal moisture availability with next upstream trough.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1210 PM EDT Sat Oct 4 2025

Dry environment within an upper ridge will allow VFR conditions
and just a few clouds in the 6-8 kft layer to persist this
weekend. S/SW winds will generally remain below 10 knots
otherwise.

&&

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

&&

$$

DISCUSSION...Marsili
AVIATION...Steinwedel