420
FXUS63 KIWX 091034
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
634 AM EDT Mon Jun 9 2025

.KEY MESSAGES...

- More showers and scattered thunderstorms this afternoon into
  early tonight

- Marginally severe storms with locally heavy rainfall are
  likely with damaging winds the greatest severe weather threat

- Very warm Wednesday and Thursday with highs in the mid 80s

&&

.DISCUSSION...
Issued at 315 AM EDT Mon Jun 9 2025

An anomalously deep upper low was near INL (International Falls,
MN) early this morning with a 5450 meter height. The surface
pressure had just dipped below 1000.0 mb. This system will work
in tandem with a short wave diving south on the back side of the
upper low system merging with a disturbance ejecting east out
of the High Plains. This combination will bring showers and
scattered thunderstorms to the forecast area this afternoon into
early tonight. As for chances for severe weather, instability
should be marginal with max afternoon CAPEs up 500 J/Kg per GFS
BUFKIT. However, the upper level flow will be quite strong with
low level bulk shear (0-6 Km) reaching 60 knots. Gut feeling is
there will be a similar scenario to yesterday but with wind
gusts a little stronger and more numerous than yesterday. A few
to several storms are likely to have wind gust between 50 and
60 mph. It looks like the most optimal time for severe storms
today is between 3 PM EDT and 9 PM EDT with the combination of
max heating occurrence and the cold front and the upper energy
arriving and coinciding.

Temperatures should reach the mid 80s Wednesday with the next
chance for rain arriving Wednesday night in the form of showers
and storms as more energy in the form of upper level trofs
arrives. At this time, it looks like the most favorable period
for thunderstorms for Wednesday through Sunday is during the
diurnal favored window between 3 PM EDT and 9 PM EDT (19Z to
01Z).

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 630 AM EDT Mon Jun 9 2025

A band of rain tied to low level baroclinic zone with lead
frontal boundary will remain south of the terminals early this
morning. Westerly low level flow in wake of this trough has
advected in a drier low level airmass into northern Indiana,
with just some scattering mid level clouds early this morning.
Looking upstream, a potent upper level short wave trough is
tracking southeast across southern Minnesota. Vorticity
advection with this feature and cooling mid/upper level temps
should act to overcome the marginal moisture setup for isolated
to scattered convection this afternoon. Given track of vort max
and position of upper cold pocket, best chance of thunder may
still be along and north of US Route 6 corridor, but both KSBN
and KFWA appear to be inline for at least narrow window of
scattered shower/thunderstorm potential this afternoon/early
evening. Dry subcloud layer and evaporative cooling processes
should pose gusty wind threat with these storms, but will hold
off on inclusion of convective gusts given lingering uncertainty
in convective coverage.

VFR conditions should hold through this period with possible
exception of brief restriction with any isolated stronger storm.
Given large depth to steep low level lapse rates, synoptic sfc
gusts will also be in an issue today with a potential of 25 to
30 knot southwest gusts in advance of the secondary cold
front/upper trough.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory from 1 PM this afternoon to 8 PM EDT this
     evening for LMZ043-046.

&&

$$

DISCUSSION...Skipper
AVIATION...Marsili