621
FXUS63 KIWX 081715
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
115 PM EDT Tue Jul 8 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 /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 130 PM EDT Tue Jul 8 2025

A shortwave trough is slowly arriving over the western Great
Lakes this afternoon. This has resulted in a few thunderstorms
over northern Illinois, tracking ENE> Mesoanalysis depicts a
narrow corridor of instability where these storms have
developed. Weak flow aloft, dry low-level air and weaker
instability over KSBN suggest this activity will fail to reach
KSBN. Nonetheless, storms will be monitored. This same trough
axis sparks more storms Wednesday afternoon, especially toward
KFWA, but is just beyond this TAF period.

&&

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

&&

$$

DISCUSSION...Hammer
AVIATION...Brown