461
FXUS63 KIWX 251057
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
657 AM EDT Fri Jul 25 2025

.KEY MESSAGES...

- Numerous showers and storms are expected this morning with
  heavy rain and isolated flooding possible.

- Warm and humid conditions will support periodic showers and
  storms through the weekend.

- Very hot and humid weather returns for Monday and Tuesday with
  heat indices likely over 100.

&&

.DISCUSSION...
Issued at 218 AM EDT Fri Jul 25 2025

The combination of a weak surface frontal boundary meandering over
the region and an exceptionally moist airmass will support periodic
showers and storms through the weekend (along with high humidity/
heat indices). PW values remain near all-time record highs for
the region with values around 2.25 inches. Forcing remains weak
through this period so timing of individual precip chances is
difficult, particularly beyond the first 24 hours. Thunderstorm
coverage will be driven largely by remnant outflow boundaries
and convectively-enhanced MCV`s rippling through the area.
Generally speaking though there does appear to be a trend in hi-
res CAM`s of best precip chances arriving during the morning
hours given some nocturnal LLJ enhancement and timing the
arrival of convective MCV`s generated by diurnal convection well
upstream. That will certainly be the case this morning. Expect
widespread convection to light up in the 07-11Z period as
shortwave presently over far western IL moves into the area.
There is a modest low level convergence signal and the
atmosphere is obviously extremely moist with MUCAPE values well
over 2000 J/kg. Minimal near-surface capping inversion will be
irrelevant to precip chances/coverage given moist/unstable
profiles aloft and elevated convergence signal. This near-
surface stable layer should limit the potential for any damaging
winds though especially given relatively light flow aloft and
virtually no organizing shear. Heavy rain/isolated flooding will
definitely be the main concern with morning activity given high
rainfall efficiency due to high PW and deep warm cloud depths,
but also low MBE velocities supporting training/backbuilding of
storms. One saving grace is that the main area of precip is
expected to be in our SE half this morning, which was largely
missed by yesterday`s convection, and has been dry over the past
several days. There are also some lingering concerns based on
newest hi-res models about just how widespread deep convection
will be and will therefore hold off on a flood watch and handle
any localized areas of heavy rain with advisories/warnings as
needed.

Minor decrease in precip coverage is possible during the late
morning but convection will likely continue to slowly bubble through
the day. A slight increase in coverage is possible during the
diurnal instability maximum late this afternoon but there is
virtually no forcing to rely on that time and expect just SCT
storms. The main threat should continue to be isolated heavy rain
given very little shear/flow aloft and generally near-moist
adiabatic lapse rates less than 6 C/km. The abundance of precip and
clouds will keep a lid on highs today with only mid to perhaps upper
80s expected. This should keep heat indices in check despite mid 70s
dewpoints. It will still feel like mid/upper 90s though so caution
is urged for anyone planning outdoor activities.

As best as we can tell at this point, Sat looks like a near-copy of
today with an uptick in convection chances during the early morning
and likely only SCT storms during the afternoon/evening. Some
hi-res CAM`s advertise an earlier arrival of nocturnal
convection, allowing for a break and "recharge" during the
middle of the day with more numerous storms during the evening.
Other solutions bring storms in during the late morning,
potentially allowing for some strong storms during the middle of
the day and then little/nothing thereafter. Unfortunately in
this pattern it`s difficult to pinpoint a solution more than day
out. Suffice it to say warm/humid conditions and periodic,
scattered storms will be possible both Sat and Sun with isolated
heavy rain continuing to be the main threat.

It does appear as though this pesky front will lift north Sun night,
placing our area more firmly in the stable (but hot) warm sector.
There is a corresponding drop in precip chances for Mon and Tue
along with heat indices more solidly around and above 100F. At least
a heat advisory will be needed with warning criteria of 105F
possible on Mon. A cold front will finally arrive sometime midweek
though timing is uncertain along with precip/severe weather chances.
There is high confidence in a period of cooler and much less humid
conditions by Thu of next week, potentially carrying into at least
the first half of next weekend. Relief is on the way.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 648 AM EDT Fri Jul 25 2025

Ongoing thunderstorms and trailing stratiform rain were causing
challenges. There were numerous outflow boundaries from
overnight convection that were laid down resulting in a somewhat
perturbed wind field over northern Indiana. Winds today will
favor the synoptic flow with light southwest winds. The
continued channel of energy topping the upstream ridge was
allowing more organized storms to form all of the way back to
southwest Kansas.


&&

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

&&

$$

DISCUSSION...AGD
AVIATION...Skipper