IWX issues Area Forecast Discussion (AFD) at Aug 27, 6:30 AM EDT259
FXUS63 KIWX 271030
AFDIWX
Area Forecast Discussion
National Weather Service Northern Indiana
630 AM EDT Thu Aug 27 2026
.KEY MESSAGES...
- Mainly dry today with just a low chance (10-15%) of a shower this
afternoon.
- Seasonable temperatures continue today through Saturday, but then
warming early next week.
- Low chance of showers and thunderstorms return late
weekend/early next week but confidence is low.
- There is a Moderate Swim risk today for southeast Lake
Michigan beaches.
&&
.DISCUSSION...
Issued at 315 AM EDT Thu Aug 27 2026
Primary near term forecast issues center on fog this morning and the
potential of an isolated shower or thunderstorm this afternoon.
Sfc pressure field has become weaker this morning in wake of weak
cold front that tracked across the area over past 6 to 12 hours.
Light winds and residual near sfc moisture have promoted some
patchy fog development across the area. Recent rainfall along
the US 24 corridor yesterday should aid in fog formation and
the southeast expansion of the patchy fog early this morning.
Issued an SPS earlier this morning highlighting rapidly varying
visibilities with patchy dense fog potential. Trends will
continue to be monitored for potential of a focused dense fog
advisory.
For today, low level cold advection will continue. Mixed layer
depths should increase enough to allow for temps to be fairly
similar to that of yesterday around the 80 degree mark. The initial
mid/upper level trough axis that aided in yesterday's showers and
storms have shifted east of the region. Water vapor imagery early
this morning does depict another upper level disturbance dropping
southeast across southern Minnesota/northern Iowa which will likely
shift across the western Great Lakes during peak heating while
another subtle mid level trough tracks across central Lake Michigan
vicinity early this afternoon. A secondary low level trough should
shift southeast across southeast Lower Michigan this afternoon in
response to this mid/upper level evolution. If decent heating, temps
in lower 80s, and steep low level lapse rates do materialize as
expected today, some isolated shower activity is possible this
afternoon/early evening particularly across NW Indiana/NE Illinois
in closer proximity to the stronger mid level trough and where some
lake reinforced boundary is possible. Confidence remains low in
coverage, and for this issuance have kept PoPs in the 10-15 percent
range. Skies should clear this evening, with some potential of
shallow patchy fog once again early Friday morning, but currently
not expecting this to be quite as prevalent as this morning.
Mid level ridging across the Corn Belt will slowly approach the
western Great Lakes late Friday/early Saturday, and approach of this
feature will result in weak low level thermal advections
Thursday night into early Saturday. A slowly modifying low level
thermal trough will allow for a continuation of near seasonable
temperatures Friday into Saturday.
Broad upper ridging is then expected to overspread mid/upper MS
Valley late weekend as a stronger upper trough across Pacific NW
lifts into south central Canada by Monday. Veering low level flow
will allow for some better moisture transport into the area late
Sunday into early Monday. Precip chances remain an item of very low
confidence however given uncertainty as to how efficient these
northern latitude short waves will dampen the upper ridge, and also
the potential of very warm mid level thermal profiles acting to
create a good deal of CIN for near sfc/sfc based parcels. It is
possible some convection for elevated parcels develops late Sunday
into Monday but greater confidence in higher PoPs may remain to the
north across the northern/eastern Great Lakes where warm/moist
advective forcing should be maximized. Broadbrushed slight
chance/low chance PoPs have been maintained through much of the
Mon-Wed period with a potential of moderate to strong
instability and an instability gradient somewhere across the
region. However, confidence in day to day PoPs remains quite low
given greater uncertainty in longwave ridge amplitude for the
latter periods. An extended period of above normal temperatures
remains in item of higher confidence for much of next week.
&&
.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 630 AM EDT Thu Aug 27 2026
Early morning stratus/fog will be the primary aviation weather
concern for the 12Z TAFs. Surface cold frontal feature has
shifted east of the terminals early this morning. As of 10Z, the
most expansive stratus/fog has occurred immediately behind the
front across extreme northeast Indiana/northwest Ohio. Across
the remainder of northern Indiana fog has been more patchy in
nature likely in part due to some increasing dry air advection
near surface creating not as favorable moisture vertical
profiles. Will need to watch for trends for potential of brief
IFR conditions at KFWA through 13Z. Otherwise, broad cyclonic
flow continues today with another short wave trough expected to
approach northwest Indiana this afternoon. An isolated shower is
possible today, but continued dry air advection and overall weak
nature to synoptic forcing/forcing mechanisms suggests any rain
showers should be of very low coverage if they occur. A weak
anticyclone will build into the region this evening providing
light and variable winds. Some patchy shallow fog may develop
again early Friday morning, but confidence in any terminal
impacts is quite low and will refrain from any 12Z TAF mention.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.
&&
$$
DISCUSSION...Marsili
AVIATION...Marsili
Source:
IWX issues Area Forecast Discussion (AFD) at Aug 27, 6:30 AM EDT---------------
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