IWX issues Area Forecast Discussion (AFD) at Sep 23, 2:11 PM EDT957
FXUS63 KIWX 231811
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
211 PM EDT Wed Sep 23 2026
.KEY MESSAGES...
- Pockets of drizzle and light rain are possible especially
along and east of Interstate 69 through early this evening.
Rainfall amounts are only expected to range from a trace to a
few hundredths of an inch.
- Seasonable cool conditions continue into the weekend with some moderation
back to temperatures around normal early next week.
- An extended period of dry weather is expected Thursday through Tuesday,
with next rain chances not until the middle of next week.
&&
.DISCUSSION...
Issued at 205 PM EDT Wed Sep 23 2026
A stagnant rex block pattern continues across the Great Lakes and
Ohio Valley today. Water vapor imagery early this afternoon indicates
two distinct short waves progressing through this pattern with the
first dropping southeast across far southern Indiana/western Kentucky
and another vort max drifting westward through the base of the northern
latitude ridge across southern Lake Michigan/SE Wisconsin. There appears
to be two distinct mid level height minima with this pattern, with
a tendency of some weak phasing through the afternoon and early
evening hours. This should result in some continued respectable low
level moisture transport from east to west across northern Indiana
and northwest Ohio through this evening. Some subtle increase
in moisture depth paired with resultant 250-500 J/kg of MUCAPE
could give rise to some isolated to scattered showers mainly
along and east of I-69 across NE Indiana/NW Ohio through this
evening. To this point, much of the precipitation has been in
the form of some patchy drizzle, and this should continue to be
the case this evening for western/central areas as the southern
Lake MI vort max begins to shift southward.
By late tonight into Thursday AM, easterly low level flow should
begin to advect drier air westward to the local area as the
Ohio Valley negative mid/upper level height anomaly begins to
become more suppressed southward. This should open the door for
some decreasing low clouds across northern half later tonight
into Thursday, but uncertainty persists with cloud cover during
the day Thursday. Guidance would suggest best chance of low
clouds lingering into Thursday afternoon would be across western
and southern portions of the forecast area. Some low level
thermal modification and likelihood of some decrease in clouds
should allow highs to be 4 to 8 degrees warmer tomorrow, but a
lower than normal confidence exists with temps tomorrow based on
the potential of that lingering low cloud cover.
Overall, very few changes are warranted for this forecast package
for Friday and beyond with a relatively stable longwave pattern
remaining in place through the weekend. This stable wave pattern
involves preference for a central CONUS ridge, with primary
negative upper height anomalies across southwest Canada and New
England. A couple of upper level short waves are expected to
eject northeast from the Pacific NW/southwest Canadian upper
trough into the Northern Plains/Upper Midwest Friday, and then
again late weekend, but persistence of the stable longwave
pattern and background mean upper ridging should result in
little in the way of notable mid/upper level forcing through the
first part of next week as these short waves dampen upstream.
Temperatures are expected to remain below normal through the
weekend in this stagnant pattern, with an opportunity for cooler
nights in the mid-upper 40s Thu night through Sat night due to
less cloud cover.
Present indications still suggest the stable wave pattern breaks
down Tuesday and beyond with more progression in the flow
developing, and the potential of more dynamic eastern Pacific waves
reaching the Upper Midwest/Great Lakes region. This likely will
represent the next notable chance of showers/embedded storms with a
potential larger scale frontal response possible by next Tue or
Wed.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 114 PM EDT Wed Sep 23 2026
Stratus persists this afternoon, but signs of improvement are
noted both in surface observations and satellite. Ceilings have
steadily risen at some stations to high-end MVFR as high
pressure to the north exerts its influence. Timing for when this
improvement occurs is low. Some degree of BKN to OVC skies
persists overnight, but medium-high confidence in VFR ceilings
owing to favorable model agreement and the aformentioned trends.
With KSBN on the northern fringe of this slow-moving low,
better chance of SCT to FEW late in the TAF period while BKN
skies linger at KFWA. Drizzle tapers off late this afternoon as
well, with very weak forcing noted overnight.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Marsili
AVIATION...Brown
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 23, 2:11 PM EDT---------------
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