375
FXUS63 KIWX 201154 CCA
AFDIWX

Area Forecast Discussion...CORRECTION
National Weather Service Northern Indiana
631 AM EDT Tue May 20 2025

.KEY MESSAGES...

- Passing showers and thunderstorms today. Rain may be heavy at
  times.

- Wind gusts from the east today at 35 to 40 mph.

- Scattered showers and thunderstorms linger in the forecast
  through at least Thursday morning.

&&

.DISCUSSION...
Issued at 415 AM EDT Tue May 20 2025

A 998mb surface low is approaching from the Kansas City area. Wind
gusts locally have been strengthening already this morning,
with wind gusts of 30-32 knots at KLAF, KVPZ, and KSBN. This is
despite soundings this hour that are rather stable. High
resolution guidance suggests this synoptic wind field will
strengthen through the morning and midday hours as the low
approaches. Wind gusts of 40 mph are expected, especially along
and west of US31. Wind will be maximized either from showers
along the incoming warm front or, should skies scatter out
briefly this afternoon in the wake of the warm front, a strong
low-level jet could be able to mix down as well. Confidence is
medium at best for how this plays out as forecast soundings are
overall rather stable, yet model agreement is high and the
existing wind field early this morning supports it.

A line of thunderstorms moving into western Indiana this hour is
exhibiting a weakening trend on infrared satellite along with a small
decline in lightning. Our local environment, with an east wind
and dew points in the low-to-mid 40s will be hostile for these
incoming storms such that a weakening trend will continue.
Showers will move through from southwest to northeast through
the morning and midday hours. As the warm sector becomes
established overhead this afternoon, scattered showers and
storms develop south of US 24 amid 500 j/kg of MUCAPE and about
40 knots of shear. Forecast soundings are generally unimpressive
locally, but small hail is a possibility from the tallest
storms and, given the strong low- level wind field, perhaps a
gusty storm collapse. Anomalously high PWATS and boundary-
parallel flow permit the risk of heavy downpours.

Scattered showers and thunderstorms taper off for a time overnight
as a dry slot attempts to move overhead. This is followed by more
shower chances Wednesday and even Thursday as the low continues its
slow trek east.

Drying out by Friday and most likely into the weekend. I`ve
maintained some low POPs for coordination purposes, but
guidance has shifted this weekend`s low pressure center farther
south such that the best rain chances overall could be well
south of US 24. An upper-level low swirling over the eastern
Great Lakes Sunday night through Tuesday brings additional
chances for rain while keeping temperatures cooler than normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 631 AM EDT Tue May 20 2025

An upper low pressure system located within a trough across the
Plains States pivots towards the area today. A surface low
pressure system develops and deepens over the area and this
allows for some rain this morning through the day before a dry
slot moves in this evening. With the rain, expect MVFR CIGs not
too long after onset, but continued positive theta-e advection
should allow times of IFR as well. Winds are expected to be out
of the east for the bulk of the period and it is also expected
to be breezy as a low level jet swings through the area. Gusts
between 20 and 30 kts are expected to be prevailing through the
period. SBN has a small chance to see LLWS with these winds, but
think the case is marginal enough to leave it out.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 9 AM EDT this morning for LMZ043-
     046.
     Gale Warning until 5 PM EDT this afternoon for LMZ043-046.

&&

$$

DISCUSSION...Brown
AVIATION...Roller