258
FXUS63 KIWX 050717
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
317 AM EDT Fri Jul 5 2024

.KEY MESSAGES...

- A chance for showers and thunderstorms exist today with the
  greatest chance occurring during the afternoon. Gusty winds
  and locally heavy rain are the main threats from storms.

- More comfortable humidity levels and leaning dry for this
  weekend.

- Our next chance for showers and thunderstorms occurs between n
  later Monday afternoon and much of Tuesday.

&&

.DISCUSSION...
Issued at 309 AM EDT Fri Jul 5 2024

With a Pacific jet across the mid and northern tier of the CONUS, an
upper low and associated strong vort max enter the Great Lakes
region today. This increased forcing pushes a cold front through the
area. With a subtropical high pressure system in the Gulf States,
the cold front is cut off from better moisture and that keeps
greater than 70s dew points south of the area today. Even still, the
ECMWF has greater than 1000 J/kg of MUCAPE and 30 kts of effective
shear for storms to work with. In looking at soundings and
hodographs on the NAM3k and HRRR, gusty to near-damaging winds could
be possible with DCAPE over 1000 J/kg, along with some small hail
likely made smaller as a result of the wetter low levels of the
sounding. Shear appears straight likely eliminating the tornado
potential. Locally heavy rainfall will also be possible. Look for
showers and potentially a few thunderstorms to arrive this morning
as an initial area of vorticity comes in from the southwest. But the
better storm chance appears to be after 18z between our western
border and IN-15, just out in front of the cold front, through
around 3z in our east. Still looks like one of the better areas for
stronger storms based on ingredients is in the I-69 corridor.

The better moisture is gutted behind the cold front for Saturday and
that likely keeps the rain chances on the low side to
potentially dry despite some delayed areas of vorticity moving
through in the flow. A cooler air mass comes in, but models
develop showers more in the morning, which is before the better
low level lapse rates develop in the afternoon. So this would
likely restrict the rain intensity and keep thunderstorms at
bay. High temperatures are expected to be in the mid 70s to
around 80 degrees, which is slightly below average for this time
of year.

Surface high pressure begins edging into the area Saturday afternoon
and evening and moves east of the area Sunday morning and this
provides a time of dry weather through this period. Then, from
Sunday afternoon to Monday morning, weak areas of vorticity move
southwest to northeast with our Lake MI-adjacent counties
potentially on the eastern periphery of their cross-hairs. Will have
slight to chance PoPs in this area during this time period, but am
not expecting any substantial rain from these opportunities given
how weak the forcing is.

Finally, better forcing arrives Monday afternoon into Tuesday as a
Pacific wave deepens the trough. The best time for instability is
Monday evening and Tuesday morning so will allow for thunderstorms
during that time frame. The aforementioned trough departs for
Wednesday and Thursday, which points to low chances for rain, if
at all. Aside from Monday, which has highs slightly above
normal, in the upper 80s, highs in the low to mid 80s will be
common Tuesday through Thursday, which is right around normal.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 155 AM EDT Fri Jul 5 2024

Quite a pot-pourri of conditions this forecast period, starting
with BR/FG troubles for the first half (MVFR to IFR likely,
possibly LIFR at KFWA), and then showers/storms this morning
and afternoon.

Visibilities around the area as of this writing range from 1/4
mile all the way up to 10 miles, likely thanks to firework
smoke and low level moisture trapped beneath the inversion.
Skies are clear in many locations as well, helping to radiate
better with the calm winds. However, a majority of the sites as
of the latest observations have 1/4 to 4SM visibility. KSBN and
KFWA have fluctuated between around 2 miles and 6 miles, and
suspect it will bounce around until sunrise. At KFWA I suspect
we have the better potential to drop to around 1 mile or even
less towards 12z, so have tempos in for that.

Otherwise our first round of possible showers would be this
morning as a decaying line of showers and storms moves into the
area. All but one of the models suggest the showers will die
before reaching KFWA, but most have it reaching KSBN (albeit
much weaker). Left thunder out for now as we`ll really be
struggling for instability-will monitor lightning trends and
adjust as needed. Later in the afternoon showers and storms are
possible, but most of the guidance keeps the better potential
east of KSBN, but KFWA looks to see showers and storms in the
18-00z window. MVFR to VFR conditions are most likely in
thunderstorms, with the occasional drops to 2SM (IFR) possible
in heaviest showers/storms.

&&

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

&&

$$

DISCUSSION...Roller
AVIATION...MCD