IWX issues Area Forecast Discussion (AFD) at Jul 13, 1:34 PM EDT680
FXUS63 KIWX 131734
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
134 PM EDT Mon Jul 13 2026
.KEY MESSAGES...
- Heat builds through the middle of the week with highs in the
upper 80s to low 90s today, and the low to mid 90s Tuesday
and Wednesday.
- Peak afternoon heat indices near or above 100 degrees on Tuesday
and Wednesday.
- The potential for showers and thunderstorms (20-40%) enters the
forecast late this week into this weekend.
&&
.DISCUSSION...
Issued at 223 AM EDT Mon Jul 13 2026
An expansive and highly anomalous mid-upper level ridge over the
Rockies and Northern Plains will fold east into the western
Great Lakes today, and the southern Great Lakes by Tuesday and
Wednesday. The surface pattern in this regime will remain
largely unchanged with high pressure in command under the
building ridge and associated subsident heat dome. The result
will be plentiful sunshine, light winds and increasingly hot and
humid conditions through Wednesday.
Whether afternoon and early evening heat indices peak into
advisory criteria (100-105F) Tuesday into Wednesday remains
uncertain given little in the way of moisture advection, and the
resulting reliance on evapotranspiration processes and more
shallow mixing depths to push sfc dewpoints up to near 70F.
With that said, latest guidance overall favors an eventual need for
a CWA-wide Heat Advisory Tuesday afternoon into Wednesday, though
opted to hold off for now per collaboration and the lingering
dewpoint spread.
The GFS remains more aggressive in breaking down the ridge and
sending a backdoor cool front into the local area by Thursday and
Friday with slightly cooler temps and non-zero (~10%) storm chances.
The ECMWF and GEM maintain stronger ridging and dry/hot conditions,
which matches latest NBM guidance. Ridge does look to fully break
down this weekend into early next week with northwest flow
potentially resulting in a frontal passage and shower/storm chances
(20-40%).
&&
.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 132 PM EDT Mon Jul 13 2026
VFR conditions are expected at the terminal. With clear skies
and light (or variable) winds, MVFR visibilities are possible
late tonight/early Tue AM, but confidence in humidity levels was
not high enough to include a mention in the TAF at this time.
Much of the guidance had 6SM or greater, with the exception of a
couple dropping to 4-5SM.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert from midnight EDT /11 PM CDT/ tonight to
midnight EDT /11 PM CDT/ Tuesday night for INZ005-012>015-
022-023-104-116-204-216.
Heat Advisory from noon EDT /11 AM CDT/ to 8 PM EDT /7 PM CDT/
Tuesday for INZ005>009-012>015-017-018-020-022>024-103-
104-116-203-204-216.
Air Quality Alert until midnight CDT Tuesday night for INZ103-
203.
OH...Heat Advisory from noon to 8 PM EDT Tuesday for OHZ001-002-004-
005-015-016.
MI...Heat Advisory from noon to 8 PM EDT Tuesday for MIZ078>081-177-
277.
MARINE...None.
&&
$$
DISCUSSION...Steinwedel
AVIATION...MCD
Source:
IWX issues Area Forecast Discussion (AFD) at Jul 13, 1:34 PM EDT---------------
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