819
FXUS63 KIWX 051338
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
938 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.

&&

.UPDATE...
Issued at 938 AM EDT Fri Jul 5 2024

Pre-frontal trough is located from roughly central Lk MI to
Chicago and east of Bloomington IL. An line of showers has been
attempting to slowly expand just ahead of this with very limited
electrical activity noted as overall instability is quite
paltry and with cloud cover ahead of the line, not overly
optimistic on evolution of this area. Several CAMs actually
weaken this line over the next couple of hours as denser cloud
cover streaming NE ahead of a somewhat more organized cluster of
storms over southern IN further impacts potential
destablization along/east of I-69. Will monitor trends, but
rather unimpressed by the setup this morning and even more
concerned that little, if anything will develop this afternoon
behind this area as the main cold front swings through. A few
CAMs try to develop isolated showers/storms, which would have a
fair amount of DCAPE to work with as noted by the overnight
forecaster, but a lack of overall shear and lower lapse rates
may limit organization.

&&

.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 /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 700 AM EDT Fri Jul 5 2024

Predominantly VFR to MVFR conditions expected at the TAF sites
today, with potential for IFR in any heavier showers/storms that
develop today. BR and fog around the area this morning will
diminish within the next hour or so, including at KFWA which
as of 11z reporting 4-6SM. Otherwise, a cold front is on our
western doorstep near Lake Michigan, and will progress eastward
through the evening. There is a break in the showers/storms
along the cold front, with areas between KMDW & KIKK currently
dry. It`s questionable whether this area will fill in as the
line moves eastward and we gain daytime heating/instability.
Carried a VCSH through 17z, then have -SHRA VCTS with a prob30
for storms 20-24z. Similarly at KFWA earlier showers are
uncertain, with increasing potential for isolated storms later
in the afternoon to impact the terminals. Some of the guidance
holds off until after 00z for storms, but I suspect the 19-23z
time frame is our best chance. Later tonight potential MVFR deck
will impact KSBN (KFWA after 12z).

&&

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

&&

$$

UPDATE...Fisher
DISCUSSION...Roller
AVIATION...MCD