IWX issues Area Forecast Discussion (AFD) at Sep 24, 12:16 PM EDT918
FXUS63 KIWX 241616
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1216 PM EDT Wed Sep 24 2025
.KEY MESSAGES...
- There are chances for rain showers today (20 to 60 percent),
with the highest chances today along and south of US 24. Lower
chances persist tonight into Thursday (20 to 30 percent).
Isolated thunderstorms are possible today and Thursday, mainly
in the afternoon. Dry conditions Friday into next week.
- Dangerous swimming conditions are expected on Lake Michigan
this afternoon into Thursday morning. See the latest beach
hazards statement for details. Moderate swim risk conditions
are expected on Thursday.
- High temperatures will range from 70 to around 80 degrees
through next week, with lows in the 50s and 60s.
&&
.DISCUSSION...
Issued at 516 AM EDT Wed Sep 24 2025
An upper level low centered over Michigan this morning will linger
through Thursday evening before weakening and lifting northeastward.
As of this writing, a stationary boundary extends from SW to NE
across our CWA, from approximately Monticello, IN through around
Fort Wayne, IN and into SE Lower MI. This boundary will slowly drift
southeast through the afternoon and stall before it finally moves
east of us overnight. Meanwhile, A surface low over MO right now
will lift northeast into South/Central Indiana and Ohio through the
evening--with the bulk of it just skirting our southeastern CWA. Cut
pops from previous forecast given the convection to our southwest
has shunted moisture axis to the ESE of our area, but still have 40-
65 percent generally along/south of US 24 (especially east of I 69)
through the afternoon. We're seeing some rain showers already with
the LLJ ahead of the boundary, and as the low lifts into IN/OH
expect we'll see this continue. Isolated thunderstorms are possible
in the afternoon.
North of US 24 (and west of I 69) we'll see a lull before additional
precipitation chances move in this afternoon. I have some areas near
the lake dry this morning, but then increasing to around 20 to 30
percent for the afternoon as a shortwave pinwheels around the upper
low just to our north. Even then, models focus the best chances
further east --some of the high res models don't even have
precipitation after 15z until late afternoon (7z HRRR). With
cyclonic flow aloft and lingering low level moisture, I'm inclined
to keep at least a 20-30 percent in the NW through today with this
secondary short wave. Further east this afternoon, have around 30-50
percent.
Otherwise, there will be fog (mostly 1-3SM visibilities) around as
the stationary boundary lingers and winds are nearly calm-however
don't suspect any large areas of dense fog to develop like we saw
yesterday. As of this writing (845Z), there are only a couple sites
reporting visibility intermittently of around 1/4 to 1/2SM--and they
are more focused near Kalamazoo, MI and into St. Joseph County, MI.
Benton Harbor has occasionally dropped overnight-but not very
persistent. I wouldn't be surprised to see a brief drop to around
1/2SM or so at some sites this morning-especially further north and
west-but not enough to warrant any kind of advisory. Right now it
seems the conditions are more favorable for a low deck of stratus
(300 ft ceilings with 2.5SM Visibility reported at KSBN at 834z, in
addition to a few other sites). If anything looks to persist after
sunrise, will handle with an SPS.
Tonight into Thursday I also lowered pops (20-30 percent), with
occasional dry periods overnight. Cyclonic flow aloft continues
aloft, though the low begins to weaken and lift northeast out of the
area by Thursday afternoon. We'll see a couple additional shortwaves
around the upper low that could kick off some showers (and maybe
isolated t-storm in the late afternoon far east), but moisture may
be limited given transport is shunted east with the exiting surface
low. Still, flow is off Lake Michigan overnight tonight into
Thursday evening, and we could pull moisture from there. The air
behind these shortwaves isn't too much cooler than what we're seeing
(around 8C at 850mb), so there won't be too much in the way of lake
instability. Models still focus pops further north closest to the
better forcing, and near the lakeshore with perhaps better moisture.
By Thursday evening into Friday, a broad ridge begins forcing its
way into the southwestern portion of the CWA-so we'll see
precipitation chances come to an end there (possibly even Thu
Afternoon). I removed all pops for Thu PM/Fri as most of the high
res and the larger scale models have little if any precipitation
showing up (and limited to Thu evening in NW OH).
The ridge expands beyond Friday and by Wednesday into Thursday next
week we are solidly under a ridge that extends from Texas into
Hudson Bay...with a surface high centered over the Great Lakes. In
fact, we end up in an omega blocking pattern with lows impinging on
either side of the ridge (one over the Atlantic, another possibly in
the Dakotas/Canadian Prairies). The GFS is less pronounced with this
ridge, but still keeps our area beneath it. There are no chances for
rain through the remainder of the period.
Temperatures this week will be in the 70s and low 80s, with lows in
the 50s and low 60s.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1215 PM EDT Wed Sep 24 2025
Lingering IFR to low MVFR stratus should mix out to low VFR this
afternoon, persisting into the evening hours. This stratus deck,
and some patchy fog, may attempt to fill back in later tonight
into Thursday morning given the moist low levels. Mainly dry
otherwise through the period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement through Thursday morning for INZ103.
OH...None.
MI...Beach Hazards Statement through Thursday morning for MIZ277.
MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT
Thursday for LMZ043-046.
&&
$$
DISCUSSION...MCD
AVIATION...Steinwedel
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 24, 12:16 PM EDT---------------
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