IWX issues Area Forecast Discussion (AFD) at Sep 1, 1:50 AM EDT828
FXUS63 KIWX 010550
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
150 AM EDT Tue Sep 1 2026
.KEY MESSAGES...
- Heat indices of 100 to 105 are forecasted Tuesday and
Wednesday afternoon in northern Indiana and northwestern Ohio.
A Heat Advisory is in effect.
- Chances for showers and isolated storms will diminish through
the afternoon.
- Isolated thunderstorms are possible Tuesday afternoon and
again Wednesday afternoon and evening, with the greatest
chances north of US Route 6. Locally gusty winds are possible,
but confidence is low on overall chances.
- Hotter and more humid conditions build through midweek,
peaking Tuesday into Wednesday when afternoon heat indices may
reach to around 100 degrees. Heat indices in the upper 90s to
around 100 may linger into Thursday mainly to the south of US
Route 30.
&&
.DISCUSSION...
Issued at 208 PM EDT Mon Aug 31 2026
Main changes from recent forecasts was somewhat higher
confidence in main axis of storms and impacts of heat/humidity
Tue-Wed.
Scattered to at times numerous showers have dotted the skies
through the morning, with the main area slowly starting to shift
east. Additional development appears to be trying to expand
in portions of NW IL to west central Lower MI in association
with a weak mid-level wave. Models doing poorly on handling
this, so confidence regarding evolution on the lower side.
Suspect at least some CIN should be in place with the morning
showers, but a pocket of clearing is noted that may help
overcome some of that. Most likely this will remain west and
north of the area, but trends will need to be watched for
possible inclusion of pops in NW areas.
Focus then shifts to concerns for heat and humidity as upper
level ridge builds north and shifts the axis of showers/storms
into WI/MI through mid week. Models seem to be leaning towards
this trend, but concerns still linger some given low confidence
in model handling of subsequent waves and pops. Also, SPC has
maintained the Marginal Risk for severe storms across the
northern half of the area (possibly overdone). After much
collaboration, it was decided to hoist a Heat Advisory from 16Z
Tue through 00Z Thu for all of northern Indiana and northwestern
Ohio where the greatest confidence exists for heat indices of
around 100 degrees to possibly as high as 105 degrees. Greatest
confidence does exist on Wed for criteria being met, but close
enough to just go with both days. Concerns could linger across
southern areas Thursday, but was decided to defer to later
forecasts.
Thereafter, additional chances for convection and/or heat
concerns will hinge on the position of the upper level ridge
resulting in sporadic pops into the weekend and somewhat cooler
temperatures.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 146 AM EDT Tue Sep 1 2026
Showers have largely diminished across northern Indiana. Some
weak renewed isentropic upglide is expected toward daybreak into
Tuesday morning, but this advective forcing appears a bit weaker
than previous few mornings. Some elevated instability will be
present, so while cannot rule out a few isolated showers and
storms across the region this morning, point probabilities are
too low for terminals for inclusion at this time. Weak warm
advection forcing continues this afternoon and some indications
in guidance of a very weak mid level short wave progressing
across the southern Great Lakes. Convective inhibition does not
look too strong to overcome today, but weakness in forcing may
be an issue in terms of convective initiation. Will continue
with dry terminal forecast at this time. VFR conditions should
persist through this period.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory from 2 PM EDT /1 PM CDT/ this afternoon to 8 PM
EDT /7 PM CDT/ Wednesday for INZ005>009-012>015-017-018-
020-022>027-032>034-103-104-116-203-204-216.
OH...Heat Advisory from 2 PM this afternoon to 8 PM EDT Wednesday
for OHZ001-002-004-005-015-016-024-025.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Fisher
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Sep 1, 1:50 AM EDT---------------
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