797
FXUS63 KIWX 020453
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1253 AM EDT Sat Aug 2 2025

.KEY MESSAGES...

- Cooler and less humid conditions this weekend.

- Dry weather continues through Monday.

&&

.DISCUSSION...
Issued at 246 PM EDT Fri Aug 1 2025

Geocolor satellite image and Aerosol optical depth satellite images
indicate some concentration of smoke over the area. There has been
some question about how far southward the plume can get with east
winds pushing it east south of the surface high and how much of the
smoke can reach the surface. Conversation in chat about the HRRR and
to a similar extent the RAP smoke models have not been handling
surface extent as well with some of our broadcast media partners
noting some better (USG threshold met) concentrations of PM2.5
across the area this morning despite the HRRR model holding
most of it aloft still. Air quality alerts have been extended
into Saturday for much of our MI/IN areas.

1030 mb surface high pressure over the Upper Mississippi Valley
today translates southeastward so that the center moves through the
area Saturday night and Sunday and ends up east of the area for
Monday. As a result, northeast winds today slowly veer more easterly
(which is a drying wind) for Sunday and this continues into the
early work week. Meanwhile, a theta-e plume is pushed up the
Tennessee river valley as a weak mid level shortwave pushes east
from the southern/central Plains area. This creates a battle ground
as the moisture plume struggles to push its way through the wall of
dry air and into our southwest by the time we get to Monday
afternoon. 60-65 degree dew points are also attempting to move
northward along with that plume. The NBM has appeared to back off
its Monday PoPs when compared to its most recent run yesterday. The
ECMWF maintains its more eastward component whereas the GFS gains
more of a southerly wind component earlier and so it brings the
moisture plume into the area much better to support a greater chance
for rain. Even still, the GFS and the ECMWF have PoPs on Monday
whereas the NBM doesn`t. The NBM finally has PoPs for Tuesday
afternoon, which does fit the atmospheric conditions a little better
as the low level jet pushes into the area from the Appalachian
and more of the theta-e plume is across the area as depicted on
the ECMWF. 500 to 1000 J/kg of MUCAPE is around for Monday
whereas 750 to 1250 J/kg of MUCAPE is around for Tuesday with
minimal shear both days so thunderstorms could be had both days
if we are able to realize storms. And there`s still another
chance for showers on Wednesday afternoon, but this one may be
more located west of I-69 where the better moisture and
instability axis resides. Now, on the backside of the trough,
for Thursday, this likely suppresses precipitation chances.

Meanwhile, our 70 degree temperatures slowly increase again as 850
mb temperatures starting around 9C increase to around 13C by the
time we get to Monday. This allows 80s to mix in and then dominate
the high temperature plot as we head into early the next work
week.


&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1250 AM EDT Sat Aug 2 2025

Went ahead and removed the 5SM HZ from the TAFs. Upstream so
far, plenty of VFR visby reports. HRRR smoke modeling suggests
some elevated wildfire smoke arrives by midday as subtle
troughing pushes in over the Great Lakes. Otherwise, at the
surface, high pressure remains in place with some passing clouds
from a weakening disturbance crossing the mid-Mississippi

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ005>009-012>015-017-018-022>027-032>034-103-104-116-
     203-204-216.
OH...None.
MI...Air Quality Alert until midnight EDT tonight for MIZ078>081-
     177-277.
MARINE...None.

&&

$$

DISCUSSION...Roller
AVIATION...Brown