209
FXUS63 KIWX 141823
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
223 PM EDT Mon Jul 14 2025

.KEY MESSAGES...

- Smoke aloft from Canadian wildfires is expected to overspread
  the Upper Great Lakes region today and into Tuesday. An Air
  Quality Alert remains in effect today for all of Michigan.
  Tomorrow, an Air Quality Action Day will be in effect for La
  Porte County, IN.

- Patchy ground fog is possible early Tuesday.

- Notable increase in humidity Tuesday and Wednesday. Heat indices
  in the 90s.

- Isolated rain/storms Tuesday afternoon south of US 30. Several
  rounds of rain/storms will be possible between Wednesday and
  Friday.

&&

.DISCUSSION...
Issued at 222 PM EDT Mon Jul 14 2025

Surface high pressure continues to keep mild temperatures,
comfortable humidity, and dry conditions across the area today. The
cold front that brought showers and a few storms to the southern
half of our area the past two days is now stalled across southern
Indiana, keeping clouds and precipitation away. Enjoy the low
dewpoints while you can today because humidity will notably increase
in the coming days. Tonight, quiet weather continues! Light winds,
clear skies, and leftover moisture near the ground will create
favorable conditions for radiation fog overnight. Patchy dense fog
will once again be possible by early Tuesday, especially in areas
south of US 30 that have had some rain over the past few days.

In addition, wildfire smoke from Canada continues to drift across
the Upper Great Lakes region. A statewide Michigan Air Quality Alert
remains in effect until midnight EDT tonight. It is possible that
smoke aloft gets down into northern Indiana and far northwest Ohio,
making for hazy skies. Surface air quality should not be impacted.
In La Porte County, IN, an Air Quality Action Day will be effect for
Tuesday, July 15th due to elevated levels of ozone caused by the
wildfire smoke.

Heat and humdiity will increase over the next few days. Southerly
low level flow and WAA wil usher in low to mid 70s dewpoints on
Tuesday and Wednesday, with a notable increase in humidity. Highs
will be in the upper 80s to low 90s, with peak heat indices in the
90s. Mid range model guidance has been persistent with an active
pattern remerging by midweek.  Isolated showers and storms will be
possible south of US 30 on Tuesday as a mid level vorticity maximum
lifts north and interacts with the still stalled frontal boundary
across central/southern Indiana. Next, a warm front will lift north
through the area Wednesday morning. With the area in the warm
sector, the aforementioned vorticity maximum will aid in
thunderstorm development as it pivots through the area Wednesday
morning. It`s possible we get a lull in precipitation during the day
with a lack for forcing, but renewed chances for rain/storms
increase Wednesday evening into the day on Thursday. More shortwaves
move through Thursday and a cold front sweeps through during the
afternoon/evening, with additional rounds of showers and storms
possible. Our typical summertime pattern of high moisture and
instability yet minimal shear looks to set up once again, so any
severe potential with these storms (esepcially on Thursday) will
likely be determined by whatever leftover mesoscale outflow
boundaries there are from piror day convection. By the weekend, dry
conditons return with zonal flow over the Upper Great Lakes.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 129 PM EDT Mon Jul 14 2025

High pressure vacates the area Tuesday morning and a shortwave
approaches from the south Tuesday afternoon. This allows for VFR
conditions through the period and for wind to stay less than 10 kts
sustained. Winds out of the west today become southeasterly Tuesday
morning. One thing that may need to be watched is for at least MVFR
BR tonight at SBN that could evolve into fog. Given low confidence,
have kept it out for now, but future shifts may want to consider it.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert from midnight tonight to midnight CDT
     Tuesday night for INZ103-203.
OH...None.
MI...Air Quality Alert until midnight EDT tonight for MIZ078>081-
     177-277.
MARINE...None.

&&

$$

DISCUSSION...Johnson
AVIATION...Roller