018
FXUS63 KIWX 130021
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
821 PM EDT Wed Jun 12 2024

.KEY MESSAGES...

- Chances severe storms late Thursday & Thursday evening with
  strong gusty winds and large hail.

- Hot & humid Sunday through Wednesday; highs around 90 to 95 with
  afternoon heat indices 95 to possibly as high as 105.

- After Thursday, storms will again be possible during the
  afternoons and evenings Sunday through Wednesday.

&&

.UPDATE...
Issued at 749 PM EDT Wed Jun 12 2024

A lake breeze-enhanced narrow convergence zone from north of
KRZL to near KGSH to KOEB is associated with some cumulus with
modest vertical growth. Other than this low level convergence,
not much else from a synoptic standpoint in terms of forcing.
Over next hour or two cannot discount at least potential of an
isolated shower along this axis. Looking upstream, an MCV
tracking across southern Wisconsin/northeast Illinois has a
small area of decaying convection associated with it, along
with an outflow boundary. Heading into the non-favored diurnal
hours this evening in terms of instability, would expect a
continued weakening trend with a low end chance of a few showers
affecting far NW portions of the area late evening. By late
tonight, westerly flow will strengthen that should allow for
more notable positive low level theta-e advection from the Mid
MS Valley. This will result in some potential of isolated
showers and thunderstorms late tonight into early Thursday.

&&

.DISCUSSION...
Issued at 1233 PM EDT Wed Jun 12 2024

Surface high pressure stretching the length of the Appalachians will
keep the region mostly dry through tonight. However, a
progressive westerly flow aloft could bring another weak wave
across the northern portion of the forecast area later this
evening with a few showers or storms. Another disturbance will
then move into Michigan around sunrise tomorrow, but is
generally expected to remain north of the area. The bigger
concern is a storm system developing over the great plains that
will move in late tomorrow afternoon and evening. Wind shear
will be favorable for organized linear convection with around 40
kts of bulk shear. Moisture and instability will also be on the
rise with dewpoints in the mid 60s. The highest CAPE will be
across northwest Indiana into southwest Michigan topping 2000
J/kg surface based. CAMs are in decent agreement bringing storms
in from the Northwest as early as 4 PM EDT. SPC keeps a slight
chance of severe storms across this area with the greatest
threats being wind and hail, although cannot rule out a few isolated
tornadoes. The severe threat should end before midnight when
the convection then transitions into more of an MCS with a
marginal risk of excessive rain.

Upper level ridging starts to shift eastward from the plains on
Friday and then builds on Saturday. It will therefore be warm
and dry to start the weekend with highs in the low to mid 80s.
Heat and humidity increases on Sunday and highs will be in the
90s. A shortwave could also bring some storms Sunday afternoon
or evening. Moisture increases further on Monday with southerly
flow, and heat indices will climb to near 100 degrees. Pop-up
afternoon convection will also be possible. Similar conditions
are expected on Tuesday and Wednesday.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 749 PM EDT Wed Jun 12 2024

A weak lake breeze combined with southerly flow on western
periphery of Mid Atlantic anticyclone has allowed for a narrow
axis of sfc convergence across northwest/portions of north
central Indiana. Best low level moisture pooling along this
convergence axis appears to have shifted just east of KSBN, and
would expect any early evening isolated shower development to
not affect the terminal. MCV remnant convection across southern
Wisconsin will also need monitoring this evening. This
convection has been in a decaying state and would expect this
trend to continue into a non- diurnally favored time late this
evening as it reaches southern Lower Michigan. A few showers are
possible late evening/early overnight across far northern
Indiana on southern periphery of this vort max, but will not
include with 00Z TAFs given expected weakening trend. Additional
isolated showers are possible late tonight/early Thursday as
westerly flow upstream strengthens allowing for uptick in low
level theta-e advection.

Greater potential for storms to affect terminals still appears
to be late Thursday afternoon into Thursday evening as an axis
of moderate instability noses into northern Indiana an advance
of a stronger short wave. Best chances of storms appear to be in
the 22Z-03Z period, and will handle this period in greater
detail with next few issuances. Some of these storms may have
some strong thunderstorm outflow winds associated with them.

&&

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

&&

$$

UPDATE...Marsili
DISCUSSION...Cobb
AVIATION...Marsili