973
FXUS63 KIWX 052341
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
741 PM EDT Tue Aug 5 2025

.KEY MESSAGES...

- Slow increase in heat and humidity over the next several
  days, peaking this weekend with highs in the upper 80s and
  heat indices in the mid to possibly upper 90s.

- While an outside chance for a shower or thunderstorm exists
  Sunday afternoon/evening, better chances likely hold off
  Monday at the earliest.

&&

.UPDATE...
Issued at 740 PM EDT Tue Aug 5 2025

Water vapor imagery early this evening depicts an upper level
wave across northern Indiana, with another upstream disturbance
back across the MS River. Weak forcing downstream of this
dampening short wave has been enough to generate some isolated
showers across far NE IN/NW OH this evening, where some weak
convergence may also be aided by slightly stronger easterly flow
downwind of Lake Erie. Another focal point for isolated showers
(more likely sprinkles), has been along Toll Road vicinity where
an axis of low level convergence has maximized and has been locally
enhanced by marine influence. These showers have been more
limited being on the northern fringe of an instability gradient
across the region, with bases likely limiting precip to
sprinkles or light rain showers. All of these localized areas of
forcing will have some diurnal dependence with the chance of
any isolated measurable precip diminishing after 01Z or 02Z.

&&

.DISCUSSION...
Issued at 248 PM EDT Tue Aug 5 2025

The end of the cooler and less humid conditions will be upon us soon
as upper level ridging slowly builds across the region. Although we
will warm up, it does not appear we will return to the sultry
pattern of past weeks, but nonetheless this weekend will likely
bring highs in the upper 80s to maybe near 90 and heat indices into
the 90s (most likely remaining below heat advisory thresholds). It
will also allow for a shifting of the wildfire smoke further north
out of our area. A bit of shallow ground fog could materialize
overnight, but forecasted lows remain well above crossover
temperatures and soundings show a very limited inversion near the
sfc that would preclude mention in the grids for now.

Low confidence exists in shower/storm chances into this evening
along and south of US-24 as well as east of I-69 tomorrow afternoon.
As noted in the earlier update, the best chance for any convection
likely resides just to our south into this evening closer to a
convectively induced boundary. Pops were lowered in most areas
earlier to reflect these trends. While I inherited a dry forecast
for Wednesday afternoon, a few CAMs hint at some widely scattered
showers and storms during peak heating prior to the upper trough
pushing east. I suspect these are overdone with our best chances (if
any) between 17 and 21Z east of I-69. After collaboration with other
offices, I will add slgt chc pops mainly in NW Ohio where the trough
axis will be approaching during peak heating.

After Wednesday. the best chances for showers and thunderstorms
into the weekend will reside in the northern Plains and
eventually the western Great Lakes by Sunday in association with
a somewhat deeper trough that will edge east. Our area should
remain dry through Sunday night, but given the proximity of the
trough just to the west, suppose a chance for showers and storms
could exist in NW areas by Sunday afternoon or evening. Better
chances are likely to hold off until the trough shifts over the
area early next week and stalls out as it runs into the
southeastern US upper ridge center. This could set the stage for
multiple rounds of showers and thunderstorms as moisture pools
along a semi-stationary boundary and PWATs near or above 2". For
the time being, slgt chc to chc pops will remain in place
Sunday into the start of next week as we watch the evolution of
the pattern.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 740 PM EDT Tue Aug 5 2025

A mid/upper level short wave is continuing to dampen across the
Ohio River Valley this evening. Despite this weakening, weak
forcing downstream of this shearing feature has combined with a
few axes of better low level convergence for some diurnally
enhanced showers/sprinkles. A modest north to south instability
gradient exists across northern Indiana, with precip across
Toll Road vicinity just too high based to tap into any
appreciable sfc based instability. The showers of note have been
just northeast of KFWA vicinity, in closer proximity to the
dampening mid/upper level forcing, and where instability is a
bit stronger. Expecting the showers/sprinkles across northeast
Indiana and closer to lake breeze enhancement to diminish with
loss of diurnal heating this evening. Have maintained the idea
from previous forecast of MVFR vsby potential at both terminals
in the 09Z-14Z timeframe as combination of good radiational
cooling conditions and residual impact of haze/smoke aloft help
to create some vsby restrictions like this morning. Another
upper level short wave is expected to build in behind the
dampening wave for Wednesday, with a potential of isolated
showers east of I-69. Instability will be a limiting factor
again leading to low coverage. Thus, will omit mention from KFWA
TAF at this time.


&&

.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.

&&

$$

UPDATE...Marsili
DISCUSSION...Fisher
AVIATION...Marsili