259
FXUS63 KIWX 181856 CCA
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
256 PM EDT Fri Apr 18 2025

.KEY MESSAGES...

- Shower and thunderstorm chances increase (60-80%) late this
  evening into early Saturday morning. An isolated severe storm
  remains possible, mainly in IN and sw MI (11pm-5am EDT).

- Cooler this weekend into early next week with best rainfall
  chances Saturday along and south of US 24, and for the entire
  forecast area Sunday night into Monday morning.

- Mainly dry with above normal temps Tuesday and beyond.

&&

.DISCUSSION...
Issued at 227 PM EDT Fri Apr 18 2025

A warm and windy warm sector this afternoon will give way to
scattered showers and storms late this evening into early Saturday
morning. Overall modest incoming forcing in conjunction with a
strong elevated mixed layer (and associated capping inversion
at its base...check out the central IL 12z sounding) still
bring significant questions on storm coverage and intensity
tonight. Synoptically...some increase in deeper ascent noted
with an incoming subtle shortwave and upper jet approaching the
Mid MS Valley. Weak height falls also overspread the area with
at least weak low level convergence with an incoming frontal
boundary and any leading pre-frontal features/outflows. Model
guidance is overall in agreement in this being enough to weaken
the cap for at least widely scattered convection late evening
into the early overnight.

Any deeper updrafts will have steep mid level lapse rates (MUCAPE
near 1000 j/kg) and 50-60 knots of deep layer shear in the 0-6 km
layer to work with. Hail appears to the primary threat initially
with activity more elevated with higher cloud bases.
However, given the aforementioned forcing limitations and strong
capping, thinking more intense convection will struggle and be
isolated and confined to mainly our IN and sw MI zones late this
evening into early Saturday morning. This lines up with SPC`s lower
end probs for severe storms tonight.

Showers, and perhaps some occasional lightning, likely lingers
through midday Saturday on the northern fringe of the main frontal
boundary sinking toward the OH River (mainly along/south of US 24).
This boundary and deeper moisture returns north late Sunday into
Monday morning with additional chances for showers and isolated
thunder. The remainder of the week will see a trend toward above
normal temperatures and mainly dry conditions in response to a more
zonal flow regime.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1218 PM EDT Fri Apr 18 2025

VFR will persist through evening before post cold frontal MVFR
stratocu overspreads the terminals late tonight. An
brief/isolated storm possible mid to late evening and kept with
prior prob30 mention. Otherwise gusty s-swrly winds aoa 25kts
will continue into sunset before diminishing some.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 11 PM EDT this evening for LMZ043-
     046.

&&

$$

DISCUSSION...Steinwedel
AVIATION...T