IWX issues Area Forecast Discussion (AFD) at Sep 5, 12:25 AM EDT787
FXUS63 KIWX 050425
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1225 AM EDT Sat Sep 5 2026
.KEY MESSAGES...
- 30-60% chance for scattered thunderstorms this morning, best
chances early north of US 30. Locally damaging winds are
possible with the stronger storms, especially over northwest
Ohio.
- A dry and cooler pattern emerges Sunday through Tuesday.
&&
.UPDATE...
Issued at 955 PM EDT Fri Sep 4 2026
First signs of convection near the IL/WI border as of 0140z,
near the Rockford area. Mid level wave and a very unstable
environment in the vicinity of a sfc boundary has aided in this
development. Last several runs of the HRRR, and other available
guidance, has been in good agreement in at least scattered
convection growing upscale into areas mainly along and north of
the US 30 corridor overnight into early Saturday morning
(04-09z), primarily on the cool side of the aforementioned
frontal boundary extending east into northern IN and central OH.
The CAPE profile remains impressive, while deeper layer
shear/forcing is once again on the marginal side. The question
is how quickly this activity can organize into a cold pool
driven MCS with an associated wind and non-zero tornado threat.
Latest guidance favors portions of our ne IN and nw OH counties
for this potential (near/north of Fort Wayne area southeast to
the Van Wert/Lima/ Ottawa), though plenty of uncertainty remains
given forcing uncertainties and how quickly any bowing segment
can materialize.
&&
.DISCUSSION...
Issued at 226 PM EDT Fri Sep 4 2026
Models continue to point towards a transition to a drier and
somewhat cooler pattern, but as has been the case the past several
days confidence in the finer details of this remain uncertain.
The quasi-stationary boundary remains in place from southern WI to
northern parts of our forecast area and into Ohio with a series of
outflow boundaries from multiple clusters of storms south of the
boundary. A line of showers and storms moved off the lake and
was progressing SE, but has underwent a weakening trend over the
past hour or so. Additional storms are trying to get going along
a outflow boundary in portions of Cass Co to Jay county IN.
Expect widely scattered to scattered storms to persist ahead of
these area with a window of little/no convection. Somewhat
better upper level dynamics and another wave arrive this evening
with limited consensus on isol-sct storms re-developing, but
timing, strength and location differences persist. Will keep any
pops no higher than chance across mainly NE half of the area
this evening with a slow southward trend overnight (and
decreasing pops). Slight risk for severe continues, but
confidence in overall threat is also low as best shear likely to
remain near the front. For Saturday, wherever the front finally
settles in late AM into the afternoon will likely see at least
some isolated to maybe scattered development. Model blend is
rather messy and although tempted to make some changes, just not
enough confidence mess with anything.
Sunday through Tuesday still appear to be cooler and less humid with
more pleasant highs in the upper 70s to low 80s and lows in the 50s
as the upper level ridge retrogrades slightly to the west. This
doesn't last long with a push back northeast occuring for the second
half of the week and subsequent return to chances for convection
and/or increasing heat and humidity.
&&
.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1225 AM EDT Sat Sep 5 2026
Scattered convection over southern Lake MI and southwest MI will
attempt to organize and slide east-southeast along a frontal
zone early this morning. Confidence on whether this activity
clips KFWA and KSBN with brief gusty winds and VIS restrictions
through 09-10z remains on the low side with TEMPO/PROB30
mentions retained. Model guidance continues to suggest a period
of MVFR cigs/vis toward daybreak into the midday Saturday
otherwise with no changes made.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
UPDATE...Steinwedel
DISCUSSION...Fisher
AVIATION...Steinwedel
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 5, 12:25 AM EDT---------------
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