636
FXUS63 KIWX 022346
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
746 PM EDT Wed Jul 2 2025

.KEY MESSAGES...

- Slight chance (10-20%) for a stray shower or storm Thursday
  afternoon.

- Hot and humid Friday into this weekend.

- More appreciable rain and storm chances (40-50%) return Sunday
  into Monday.

&&

.UPDATE...
Issued at 740 PM EDT Wed Jul 2 2025

Regional radar mosaic this evening indicates bulk of isolated-
scattered showers and thunderstorms have been confined to
central Lk Michigan vicinity extending eastward to south of
Saginaw Bay region. A couple of short waves in northwest flow
across the Great Lakes region have dampened short wave ridging
enough to allow for cooler mid level temps across central Lower
MI and more favorable sfc based instability for isolated showers
and thunderstorms. An isolated shower appeared to have
attempted to develop across LaPorte County past few hours along
a line of enhanced cu associated with a Lake Michigan aided sfc
trough axis. However, more limited instability with southward
extent has limited any shower development. Another convectively
enhanced short wave from last night`s central Plains convection
is tracking through central IL with a high based cloud deck
tracking across central Illinois. Can also not completely rule
out a brief shower downstream of this feature, but instability
magnitudes are even more limited south of the US 30 corridor.
Thus, will keep PoPs below mentionable level for the evening
update.

&&

.DISCUSSION...
Issued at 245 PM EDT Wed Jul 2 2025

A mid level impulse tracking east-southeast through the central
Great Lakes will force a subtle (lake breeze enhanced) sfc trough
into areas mainly along/north of US 30 late this afternoon into this
evening. This feature may be enough to generate a stray shower or
two as cooling aloft potentially breaks cap in place, but nothing
more given the weak forcing and overall dearth of moisture and
instability.

Thursday will feature slight warmer conditions as heights rebound
aloft in wake of this evening`s shortwave. Boundary layer
moisture/instability will also see a bit of an uptick near a
boundary leftover across the Upper Midwest southeast into the lower
Great Lakes. An isolated shower or storm could focus near this
boundary and/or lake breeze during peak heating with PoPs limited in
the 10-20% range given an overall lack of flow/shear/forcing, along
with a tendency for dewpoints to mix out more than modeled for
lesser MLCAPE magnitudes locally.

A warmer, more humid air mass does become better established into
Friday and Saturday as an Intermountain West upper ridge folds east
into the Great Lakes and Ohio Valley. Friday is the transition day
with high temps and PM heat indices dependent on any lingering
convective cloud debris or outflow on the leading edge of the capped
heat dome. Continued to cap PoPs at 10% (silent) with NBM`s highs
near 90 reasonable for now. Higher confidence in Saturday being the
warmest day with PM heat indices in the mid 90s to near 100F under a
mostly sunny sky as low levels moisten within increasing southwest
flow.

Guidance does continue to flatten the ridge into Sunday and Monday
allowing an frontal boundary to drop into the vicinity with
chances for scattered convection.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 740 PM EDT Wed Jul 2 2025

A couple of disturbances in west-northwest flow aloft will
continue making their way across the southern Great Lakes region
into this evening. One of these waves is dropping across eastern
Wisconsin with a few isolated showers and storms developing in
advance of this feature over the past few hours. Forcing from
this wave arrives just after peak heating across northern
Indiana, but given some weak 500-750 J/kg surface based
instability over next few hours, cannot completely rule out an
isolated shower developing in vicinity of lake-breeze enhanced
sfc trough. Some mid level subsidence/weak mid level inversion
may be a bit too much to overcome for any isolated shower
potential however. Another short wave tracking across central
IL appears to be tied to remnants of old convectively enhanced
short wave from last night`s Central Plains convection. This
forcing is entering an even less favorable downstream airmass
in terms of instability. Given very limited coverage with any
showers through mid evening will maintain a dry forecast for
terminals.

Mean ridge position should be far enough west for perhaps a
slightly greater isolated shower/storm coverage scenario
tomorrow afternoon and early evening, but overall weak forcing
mechanisms and limited instability argue for continued dry
terminal forecast through the period. West winds around 10
knots will become light this evening, with northwest winds of
up to 10 knots again on Thursday as mixed layer develops.

&&

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

&&

$$

UPDATE...Marsili
DISCUSSION...Steinwedel
AVIATION...Marsili