505
FXUS63 KIWX 090548
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
148 AM EDT Wed Jul 9 2025

.KEY MESSAGES...

- Seasonably warm & humid conditions will persist, with daily
  maximum heat index values in the upper 80s to around 90
  degrees.

- An active weather pattern will return on Wednesday, resulting
  in frequent for showers and thunderstorms over the next
  several days.

- Severe weather chances are expected to remain low. However,
  locally heavy rainfall may become a concern this weekend.

&&

.DISCUSSION...
Issued at 130 PM EDT Tue Jul 8 2025

An active weather pattern will return to the area over the next
several days with the passage of numerous mid and upper-level
disturbances. A well-defined short wave trough axis will
traverse the area this afternoon and evening, with numerous
showers and storms likely developing upstream across IL. Most
high-res models suggest this activity should dissipate or at
least weaken significantly prior to reaching our western zones
after 00z w/ the loss of diurnal instability, but nonetheless a
few light showers will remain possible through the night across
the entire CWA. Isolated to widely scattered storms will be a
possibility again during the late afternoon and early evening
hours on Wednesday with a subtle ripple in the flow / weak vort
max on the back side of the aforementioned trough. After a brief
lull during the day on Thursday, models suggest a rather complex
pattern evolution w/ two highly energetic southern and northern
stream disturbances interacting over the central plains. While
the exact evolution of this pattern remains a bit muddy at this
time, precipitation chances should increase markedly especially
from Friday night through Saturday. Forecast vertical profiles
appear extremely moist with very tall/skinny CAPE profiles,
supporting a threat for locally heavy rainfall which is
highlighted in the latest WPC Days 4/5 excessive rainfall
outlooks. At this time, this does not appear to be a widespread
heavy rain event though w/ the latest NBM spectrum suggesting
only around a 20% chance of exceeding 0.5 inch QPF across much
of the area despite a few deterministic runs hinting at much
more robust totals. Otherwise, seasonably hot and humid
conditions will persist w/ the more substantial humidity
arriving in time for the weekend which may help push heat
indices into the lower 90s.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 145 AM EDT Wed Jul 9 2025

A convectively enhanced short wave will continue to track across
northern Indiana this morning with some scattered showers and
isolated thunderstorms. Instability is a limiting factor
however, with CIN for near sfc based parcels persisting.
Confidence at this time is too low for inclusion of showers at
terminals overnight, but trends will continue to be monitored
through the daybreak. The best chance may be at KSBN where
remnant MCV feature across NE Illinois could speak some early
morning showers/isolated storms. Broad upstream upper trough
will take a baggy sfc trough/cool front into northern Indiana
today with a diurnal uptick in showers and embedded storms
expected. This potential appears to affect both terminals and
will continue idea from previous forecast in PROB30 mention
through mid/late afternoon at KSBN, and mid afternoon through
early evening at KFWA based on frontal timing. Drier low level
air will eventually seep into northern Indiana tonight behind
this front. This setup could yield some patchy shallow fog
development across NE Indiana early Thursday morning but this
will be addressed in next TAF issuance.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Hammer
AVIATION...Marsili