IWX issues Area Forecast Discussion (AFD) at Sep 30, 1:39 AM EDT054
FXUS63 KIWX 300539
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
139 AM EDT Wed Sep 30 2026
.KEY MESSAGES...
- Increasing chances (40-80%) for showers Wednesday along and
north of US 24 , best potential near Lake MI in the mid-late
afternoon. Highs will be in the upper 60s, low 70s for those
areas. South of US 24 expect highs in the mid-upper 70s with
increasing clouds.
- Rain chances (40-90%) spread eastward through Friday, with
isolated thunderstorm potential (non-severe). Highs will be in
the 70s, low 80s on Thursday and the 60s Friday.
- Dry conditions are expected this weekend into early next
week, with highs in the 60s, low 70s (warmest further south).
Overnight lows will drop into the 40s.
&&
.DISCUSSION...
Issued at 451 PM EDT Tue Sep 29 2026
Main change to the forecast was to increase rain chances Wednesday
afternoon-early evening for areas north of US 24, with the best
potential closer to Lake MI. Models have shifted southeastward with
the precipitation from previous runs, with a weak shortwave riding
the ridge stalled to our southeast. Simultaneously, moisture return
ahead of Polo remnants in the southwest and return flow around the
high coming off the Gulf take aim right into our northwest late
tonight into Wed, providing enough moisture/lift for precipitation.
Instability is still limited at the surface, with weak mid-level
lapse rates, so kept any thunder mention out for this period. Highs
north of US 24 will be in the 60s, low 70s. South of US 24, expect
mainly increasing clouds and highs in the mid-upper 70s/low 80s.
There could be a lull in precipitation after 8pm EDT as the wave
exits (subsidence) and moisture transport slows before the LLJ kicks
in again. Otherwise, we remain on the ridge/trough boundary and
continued moisture transport/warm air advection through Friday
morning, when the frontal boundary and upper trough finally press
southeastward, leaving us with some breezy northwest winds and a
gradual drying trend into the afternoon. Gradually, pops will expand
southeast Thursday afternoon-with much of the area in 60-90% chances
into Friday morning. Highs on Thursday look to be in the low-mid 70s
north of US 24, and the upper 70s, low 80s further south. Behind the
front on Friday, highs will be in the 60s.
A surface high builds in Friday afternoon into Sunday morning,
bringing a return to dry conditions. It will be cooler, with highs
in the 60s, low 70s. Flow aloft is slightly cyclonic or more zonal
during this time, with another wave (and surface low) drifting
across northern Lower and Upper MI Sunday morning, then drifting
into Ontario/Quebec by Sunday night. Most of the guidance keeps our
area dry for now, with the better forcing/precip chances further
north into MI. Troughing lingers aloft until Monday evening when
another upper ridge builds in with surface high pressure sprawling
across the GL through mid next week. High temperatures will remain
largely in the 60s, with lows in the 40s. It's possible we see
widespread lows in the upper 30s, low 40s on Monday night
(especially in MI counties).
&&
.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 130 AM EDT Wed Sep 30 2026
Light rain showers currently observed on latest radar imagery
just to the northwest of the CWA over northern IL and pushing
slowly northeastward into central MI. These showers are on the
northwestern periphery of ridging in place further south and
east. Showers look to remain light as the showers push further
southward over mainly areas near Lake Michigan and into KSBN, so
at this time think conditions will mainly remain VFR however
some slight reductions in vsbys due to rain showers may allow
for MVFR vsbys but at this time confidence remains low. At this
time KFWA looks to remain dry with the ridging in place over
south and eastern portions of the CWA.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...MCD
AVIATION...Andersen
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 30, 1:39 AM EDT---------------
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