IWX issues Area Forecast Discussion (AFD) at Sep 23, 12:31 PM EDT
313
FXUS63 KIWX 231631
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1231 PM EDT Tue Sep 23 2025
.KEY MESSAGES...
- An active weather period will continue through Friday with
numerous showers and scattered thunderstorms. Severe weather
is not expected at this time.
- High temperatures will range from 70 to around 80 degrees,
with lows in the 50s and 60s.
&&
.DISCUSSION...
Issued at 452 AM EDT Tue Sep 23 2025
Dense fog advisory continues this morning for northwest Ohio
counties; Hillsdale County, MI; and Indiana counties generally
along/east of I 69 in the north; then along/south of US 24
elsewhere. Visibilities have been generally been between 1-3SM with
drops to around 1/2SM or less becoming more frequent with time.
Didn't add any counties with this update as it seems most of the
area outside of the advisory is lingering 1-3SM or more (as of 9z).
Additionally, based on the latest guidance I think the
expiration time of 14z is still reasonable, and will let the day
shift decide whether to keep it going beyond that.
Otherwise, precipitation chances persist through Friday. A cold
front stemming from a surface low over central Lake MI (between
Green Bay, WI and Frankfort, MI as of 5z) will drop southeastward
today, reaching our northwest by around 4-8 pm ET. It will continue
southeastward overnight, extending from near Toledo, OH
southwestward through Lima, OH and Portland, IN by 8 am ET Wed.
Relatively zonal flow at 500mb today will gradually be replaced by a
cut off low embedded within a long trough that encompasses the
entire Great Lakes down into the central/southern plains. The center
of the low is expected to linger over Lower Michigan Wed-Thu before
it weakens and lifts northeastward out of the area Thursday night
into Friday morning. At the 300mb level we have a straight/slightly
cyclonically curved jet streak that develops over Lower MI, and
another ejecting from the central plains into IL/south and central
IN by 12z Wed...which will provide us with better synoptic forcing
for precipitation particularly where any coupling occurs. The best
DPVA associated with our 500mb trough develops over the western CWA
around 21-00z today, and depending on moisture/potential AM
precip/cloud cover we'll see between 500-1200 J/kg MUCAPE in that
region by the afternoon and early evening. With the arrival of the
surface cold front in our northwest, think we'll have a shot at some
showers and a few thunderstorms this afternoon, with the boundary
shifting southeast overnight. Have chances in the 30-50 percent
range through this afternoon, increasing to 60 to 70 percent
overnight. Thunderstorms are possible, but it will depend on how
much instability we can get this afternoon which might be more
difficult given the foggy/cloudy start (especially in the S-SE).
In regards to this morning/early afternoon chances today-I am less
confident as forcing is limited to the outflow boundary from last
night's convection until around 18-21z with arrival of the front.
For now, have 20-30 pops extending through the early afternoon
(increasing closer to 18z), with isolated thunderstorms after 15z.
As the stronger upper level forcing really strengthens with the
potentially coupled jets and DPVA from the digging trough through
Wednesday, a surface low develops somewhere in MO/Southern IL/IN
(00z Wed) and lifts northeastward into the Lower Great Lakes/NE
CONUS Thursday into Thursday night. This weak low will likely ride
up along/just south of the aforementioned stalled cold front that
becomes stationary in our far SE near Lima, OH--which puts our area
on the north/backside of the low as it passes through Ohio.
Additionally, with the upper low just north of us, we experience
several shortwaves that swing through in the wake of the main
surface low, prolonging precip chances into Friday morning.
The result of this will be likely to categorical rain chances Wed-
Thu, tapering off gradually through Friday morning. There could be
some lake enhancement behind this with north-northwest winds behind
the system, however there isn't much in the way of colder air behind
it, and height rises quickly overtake the CWA (from W to E) through
much of Friday-Saturday. If the ECMWF is right and the trough/system
exits slightly slower, we could see some pop up showers and isolated
storms South of US 24/east of I 69 Friday afternoon with peak
daytime heating and lingering upper level support. Confidence is low
in that occurring.
There is another trough that passes north with another low over
James Bay Saturday afternoon, but model guidance keeps us dry with
the best forcing north and our area being just enough under height
rises that it keeps precipitation out. Mainly have an uptick in
clouds at that time for this update. High pressure builds in for
Sunday into next Tuesday, so we'll be drying out once again.
High temperatures this week will range from the 70s to around 80
degrees, with lows in the 50s and 60s.
&&
.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
slowly dropping sout
Issued at 1231 PM EDT Tue Sep 23 2025
Showers and isolated storms will remain in the vicinity of KSBN
this afternoon near a weak mid level trough and sfc boundary.
This boundary and/or any outflows are expected to near KFWA by
late this afternoon and evening with chances for a few showers
or storms by this time. Mainly VFR outside of any convection
otherwise at each terminal into this evening, with lingering
MVFR stratocu at KFWA likely mixing out by TAF issuance.
A low pressure system, currently over the Central Plains, ejects
east through the OH Valley later tonight into Wednesday morning
with a period of rain likely clipping KFWA with at least MVFR
conditions. Lower confidence at KSBN with the bulk of the
moisture potentially bypassing south.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...MCD
AVIATION...Steinwedel
Source: IWX issues Area Forecast Discussion (AFD) at Sep 23, 12:31 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202509231631-KIWX-FXUS63-AFDIWX)
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