825
FXUS63 KIWX 131733
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
133 PM EDT Sun Jul 13 2025

.KEY MESSAGES...

- Some renewed low chances of showers (20-40%) and a slight
  chance of thunderstorms (10-20%) for later today into tonight,
  mainly along and south of US Route 24.

- Brief relief from higher humidity today into Monday but peak afternoon
  heat indices return into the 90s for Tuesday and Wednesday.

- Some smoke aloft from Canadian wildfires is expected to spread
  across the region today, particularly across the Great Lakes.

- Chances of showers and a few storms return Tuesday, but
  greater chances expected by midweek.

&&

.DISCUSSION...
Issued at 356 AM EDT Sun Jul 13 2025

A couple of weak sfc troughs/cool fronts persist across the
region this morning. The first of these troughs is shifting
across northwest Ohio and far northeast Indiana, roughly
extending from Defiance OH to Marion IN as of 07Z. A few light
showers appear to be trying to develop along this weak
convergence zone. A second reinforcing sfc trough, appearing to
mark more of a low level moisture gradient, is positioned back
across northwest Indiana/SW Lower Michigan. Instability profiles
are more limited with this area of convergence however. Have
kept in "silent" 10 PoPs across NE IN/NW OH for next few hours
as expected coverage will likely be below mentionable levels.

Otherwise today, primarily low level theta-e gradient is
expected to set up across central Indiana and will be watching
the northeast evolution of a mid/upper level trough across
northern Missouri. A portion of this vort max should get
ingested by a broader northern stream trough working across the
Upper Midwest/northern Great Lakes. As this occurs, some renewed
low level moisture transport will work back northward across
the Ohio River Valley and into portions of northern
Indiana/northwest Ohio, especially along and south of the US 24
corridor into this evening. Given shearing nature of the
forcing, forecast confidence was low in the northward extent of
higher chance PoPs later this afternoon into this evening. How
quickly these features phase may dictate northward extent of
mentionable PoPs. However, given this renewed moisture
transport, sheared vorticity lifting across the area, and some
support in right entrance region of larger scale upper jet, did
maintain low-mid range chance PoPs across the south later today
PM into early Monday. A few storms are possible particularly
late afternoon into this evening with some indications in
guidance of 500-1000 J/kg sfc/near sfc based CAPE. Best coverage
may end up being late evening/early overnight, when weak low
level moisture convergence at nose of weak low level jet is
maximized. Otherwise today, some increase in clouds is expected
as low/mid level moisture transport returns, with smoke aloft
from Canadian wildfires shifting across the Great Lakes. An Air
Quality Alert remains in effect for Michigan today through
Monday morning.

Isolated shower potential could persist across the far
south/southeast into early Monday, but otherwise dry conditions
and decreasing clouds are expected in the afternoon as the
sheared positively tilted trough shifts east of the area. Large
scale mid/upper level ridging will build back into the region
Monday night. Guidance is in agreement that another cut off vort
max across the southern Plains will enter this weak steering
flow and slowly lift north to the Mid MS River Valley Tuesday
evening. This should allow a northward return of the richer low
level moisture back into the local area later Tuesday/Tuesday
night. Previous forecast already included low chance PoPs
Tuesday into early Wednesday morning which appears appropriate.
Heat and humidity will be on the increase Tuesday/Wednesday with
some low-mid 90s heat indices possible during this time.

Overall medium range guidance consensus has been consistent with
an active eastern Pacific pattern for midweek, which will
eventually allow longwave ridge to dampen, and another fropa
some time in the late Wednesday/Thursday period. This could
result in more organized convective potential heading into this
period.

The main short wave track will remain across northern tier of
states for Thursday into next weekend, which would conceptually
keep local area in fairly strong baroclinic zone resulting in
some susceptibility to additional shower/storm chances. For
this reason, have accepted the blended guidance broadbrush PoP
inclusion for much of the long term period with difficult in
timing any higher probability chances at this forecast distance.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 133 PM EDT Sun Jul 13 2025

A shortwave approaches from the southwest and provides an area of
showers and perhaps a few thunderstorms to areas south of US-24,
however, models do appear to keep the storms south of FWA so will
keep the threat out of both TAFs this time. As a result, VFR
conditions will prevail as mid level cloud decks move in for the
afternoon with the arrival of the shortwave. CIGs drop as we head
into the overnight and winds relax. A few short range models are
creating fog once again this evening, but a theta-e boundary bisects
the area into north and south regions tonight right overhead of FWA.
This environment should keep even FWA out of fog chances as well so
will continue with the prevailing VFR conditions. Winds stay under
10 kts for the period.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...Air Quality Alert until midnight EDT Monday night for
     MIZ078>081-177-277.
MARINE...None.

&&

$$

DISCUSSION...Marsili
AVIATION...Roller