Mill Grove, Indiana Weather Forecast Discussion

168
FXUS63 KIWX 192328
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
728 PM EDT Fri Sep 19 2025
.KEY MESSAGES...
- Another warm day on Saturday with highs into the 80s.
- Low chances (20-40%) for showers and isolated storms enter the
  forecast into mainly western IN and southwest MI on Saturday.
- Daily chances (40-60%) for showers/storms Sunday through Tuesday.
&&
.DISCUSSION...
Issued at 214 PM EDT Fri Sep 19 2025
A persistent blocking pattern that has provided the area with upper
ridging and associated warm/dry wx gradually breaks down into this
weekend as broad troughing over the northern Plains finally releases
east into the MS River Valley and western Great Lakes. The upstream
leading warm front and moisture axis makes slow inroads into western
IN and sw MI later tonight into Saturday morning, nearing the I-69
corridor by Saturday afternoon-evening. The largely elevated nature
to the moisture advection and northwest bypass of more pronounced
vorticity advection warrants holding on to lower end PoPs (20-40%)
for scattered showers along this weak warm front. Guidance does
hint at some weak diurnal instability developing on Saturday
for a non-zero iso thunder risk west of I-69, although our
recent dry spell hints at a greater mixout of mid-late day sfc
dewpoints than modeled. Another warm day otherwise on Saturday
with at least a partly to mostly cloudy sky.
Chances for much needed rain/iso storm chances do increase Sunday
through Monday night. Deeper moisture advecting in, and numerous
vorticity maxima tracking through in broad cyclonic flow, will
provide these periodic shower/storm chances. There will be dry
stretches in between these smaller scale (convectively augmented)
mid level impulses, with ensemble guidance pointing to Sunday and
Monday aftn-night for higher measurable rain chances (50-60%).
Slight cooler highs, yet increasingly humid, the story otherwise
during these periods.
Forecast confidence quickly diminishes Tuesday through Friday as
renewed riding over southern Canada eventually cuts off an expansive
low/trough somewhere across the Mid MS and OH Valleys. Models always
struggle with these cut off, meandering, lows at this range. Opted
not to veer from daily NBM rain chances (20-50%) as a result with
the trough and frontal zone in the vicinity. Temperatures hover
pretty close to seasonal norms otherwise for the mid-late week
periods.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 728 PM EDT Fri Sep 19 2025
On east and southeast trajectories, initially the mind goes back to
a couple days ago where we advected the marine westward to get more
moisture to trap underneath the inversion, which created a few hours
of morning fog. This time, however, winds are forecast to be
stronger as a low level jet edges eastward into the area from the
slowly arriving trough to our west. So, with winds forecast to
maintain speeds above 5 kts, will leave a mention of fog out of the
TAFs. Wind speeds will need to be watched, however, because if the
inversion takes hold sooner, we could be in for another batch of fog
at least at FWA as the SREF 1 mi probabilities show for tomorrow
morning. NAM Bufkit soundings show at least the formation of shallow
fog at both sites, but cross over temps are not conducive at either
site unless radiational cooling can take effect with weaker winds.
All that aside, will be going with prevailing VFR conditions
because, while a shower or storm is possible mainly at SBN tomorrow
afternoon, the possibility of reduced flight conditions is not high
enough for its inclusion. Will be using a second group to handle the
slow veering of winds toward southerly by the late afternoon.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ005>009-012>015-017-018-022>027-032>034-103-104-116-
     203-204-216.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Steinwedel
AVIATION...Roller

NWS IWX Office Area Forecast Discussion