IWX issues Area Forecast Discussion (AFD) at Jul 18, 10:07 AM EDT009
FXUS63 KIWX 181407
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
1007 AM EDT Sat Jul 18 2026
.KEY MESSAGES...
- Smoke from Canadian wildfires will continue to bring periods
of poor air quality and reduced visibility through at least
Monday.
- Slight chance for severe storms this afternoon into the
evening. Damaging winds and heavy downpours will be the main
threats.
- High swim risk conditions are expected by this afternoon along
Lake MI beaches in Berrien County, MI and La Porte County, IN
by late afternoon and evening. Moderate swim risk conditions
are expected before that. Dangerous waves and currents are
expected.
&&
.UPDATE...
Issued at 1006 AM EDT Sat Jul 18 2026
2 features of interest being monitored this morning. The first
is a pre-frontal trough extending from Chicago to Flint MI.
Showers and storms have persisted further north, but despite
their best efforts new development to the SW has struggled. CAMs
vary considerably on what, if anything, this feature will do as
it progresses south and likely stalls or washes out. While not
confident, have maintained some slgt chc pops into early
afternoon. The main cold front, currently from northern Lower MI
to SE Wisconsin, will continue its track SE and become the
primary focus for showers and storms this afternoon. Models also
vary with this feature on timing of initiation as subsequent
location with a trend for development near/south of US-6 and
then progressing south. Plenty of instability will exist with a
stronger low level flow to not only keep storms moving but allow
an increased risk for damaging winds. The greatest threat for
more widespread wind damage resides just to the east of our area
where an Enhanced Risk exists. Over our area, there was no
changes to the SPC DY1 outlook. Again, made some token changes
based on current models trends this afternoon to pops, but given
lower confidence in where storms develop didn't go crazy with
modifications.
&&
.DISCUSSION...
Issued at 515 AM EDT Sat Jul 18 2026
A shortwave trough moving through the cyclonic flow on the
eastern side of high amplitude ridging over the Plains and into
central Canada. A cold front associated with this shortwave will
begin to push south into our area around midday. SBCAPE values
of 2500-3000 J/kg will be available along with bulk shear
values of 25 to around 50 kts. Surface dew points in the mid 70s
will provide ample moisture and PW values are around the 2 inch
mark today. Storms today should have a fairly progressive speed
so will help keep the flooding risk a bit lower than the last
couple of days when the steering flow was much slower. Helicity
values are forecast to be only around 50 m2/s2 which will keep
the risk of tornadic activity low. However, with any boundary in
close proximity to storms there could be an isolated brief spin
up or two. Lapse rates of 6.5-7.0 deg/km will help to allow for
some hail production however not ideal for large hail especially
with the very humid and warm lower levels but the melting of
hail coupled with the heavier downpour potential will make
outflow gusts the biggest threat with the storms today. SPC did
add a fairly small section of enhanced to our far eastern
portions of the CWA in Henry and Putnam counties of Ohio with
the better dynamics further east of our area. However, the
majority of the area is currently under a Slight risk today.
In the wake of the cold front as it pushes southward a more
northerly flow will arrive and this will make for hazardous
beach conditions over the southeastern Lake Michigan and wave
heights from 3 to 6 feet on the big lake. A Beach hazards
statement has been issued to address this threat as well as a
Small Craft Advisory. Drier airmass will also accompany the
frontal passage.
Sunday will be a bit cooler and drier with a more northwesterly
flow aloft and high temperatures will be mainly in the low to
mid 80s and dew points only in the 60s. We will also see a short
break in precipitation chances on Sunday into Monday before
another trough pushes into the lower Great Lakes region on
Monday evening. This will also bring another chance of showers
and thunderstorms to the area. A few of the storms may become
strong to severe so will need to watch this in the coming days.
A northwesterly flow aloft sets up again over the region by
Tuesday and remains through the rest of next week and this will
help to keep temperatures slightly cooler to near normal values.
&&
.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 625 AM EDT Sat Jul 18 2026
Mostly VFR conditions expected through at least 15z today. A
cold front will push southward after this time and bring
scattered thunderstorms into the area as it pushes south through
the evening period. MVFR to IFR vsbys in any thunderstorm
downpours along with MVFR cigs. Mainly VFR conditions should
return after the cold front pushes south through the area after
21z Sat for KSBN and after 01z Sun for KFWA. Gusty southwesterly
winds early for both TAF sites before a shift to more
northwesterly post frontal. Gusts up to 25 kts possible
especially within or near thunderstorms.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
Beach Hazards Statement from 7 PM CDT this evening through
late tonight for INZ103.
OH...None.
MI...Air Quality Alert until midnight EDT tonight for MIZ078>081-
177-277.
Beach Hazards Statement from 5 PM EDT this afternoon through
late tonight for MIZ177-277.
MARINE...Small Craft Advisory from 2 PM this afternoon to 5 AM EDT
Sunday for LMZ043.
Small Craft Advisory from 5 PM this afternoon to 5 AM EDT
Sunday for LMZ046.
&&
$$
UPDATE...Fisher
DISCUSSION...Andersen
AVIATION...Andersen
Source:
IWX issues Area Forecast Discussion (AFD) at Jul 18, 10:07 AM EDT---------------
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