958
FXUS63 KIWX 221824
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
224 PM EDT Sat Jun 22 2024

.KEY MESSAGES...

* Relief from the heat arrives later tonight through Monday, but
  briefly returns on Tuesday when afternoon heat indices may
  once again near 100 degrees.

* Showers and scattered storms expected to move in tonight with
  some potential for wind gusts in excess of 50 mph late
  evening into early overnight hours, best chances in nw IN and
  sw MI.

* There are chances for thunderstorms Tuesday into Wednesday,
  though confidence regarding timing and intensity is low at
  this time.

&&

.DISCUSSION...
Issued at 224 PM EDT Sat Jun 22 2024

No changes in thinking from the previous forecast. Shortwave and
associated deepening sfc low tracking east through the northern
Great Lakes will drag a convective outflow and synoptic cold front
southeast through the area tonight into Sunday. This will bring
rain/storm chances and at least a brief reprieve from the heat.

Dry, hot and somewhat breezy conditions will persist this afternoon
into most of the evening given a capped/dry airmass with 700 mb
temps near 10-11C. Attention late this evening into early Sunday
turns to a line or cluster of deep convection organizing over
eastern IA, southern WI and northern IL during the late aftn hours.
Expectations are for this activity to undergo a general weakening
trend with southeast progression as it outruns more favorable
flow/forcing into much less downstream instability. With that said,
if a more organized upstream convective segment is realized, the
potential for isolated severe wind gusts would exist for areas
mainly northwest of US 24 in the 03-07z window. Non-severe gusts in
the 30-50 mph range appear more likely however with what should
become an outflow dominant convective line. Opted to hold with
likely to categorical PoPs otherwise along the pre-frontal feature
early Sunday given ample pooled moisture.

The main cold front then follows through Sunday morning into early
Sunday afternoon with additional non-zero chances for scattered
showers/storms. A turned over airmass and weakened frontal
convergence behind the early AM composite outflow limits
chances/coverage however. Drier and cooler air (seasonable) does
settle in Sunday afternoon, and more into Monday when sfc high
pressure briefly builds in with pleasant wx.

Return flow quickly ramps back up in response to the next round of
Upper Midwest and Northern Great Lakes height falls. This will allow
a frontal system, first as a warm front and strong low-mid level
theta-e advection late Monday night into Tuesday, followed by a cold
frontal passage Tuesday night or Wednesday to potentially impact the
local area. This type of evolution points to several MCS`s during
this time which will no doubt modulate the positioning/timing of
these frontal features and degree of heating/destabilization.
Confidence in temps and shower/storm chances remain very low as a
result at this forecast range. Higher confidence however in
seasonable temps and dry conditions to follow for the second half of
the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 121 PM EDT Sat Jun 22 2024

We`ll start the period with VFR conditions as high pressure keeps
the area dry. However, a cold front arrives around midnight
and this may provide showers and thunderstorms to the area. At
this point, feel more confident in SBN getting thunderstorms and
perhaps some MVFR VISBY reductions (in a tempo group). FWA
appears more likely to receive showers as the line looks to
become outflow dominant and lose its strength between SBN and
FWA. Either way, have more confidence in a deck of MVFR CIGs
starting just after 10z at SBN and around 12z at FWA. Moderation
back to VFR will be possible in mid to late morning as the
front continues to sink southward. Winds, initially
southwesterly with gusts up to 25 kts today, will veer more
westerly and northwesterly behind the front on Sunday with
gusts up to around 25 kts once again.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for
     INZ005>008-012>015-020-022-023-103-104-116-203-204-216.
     Excessive Heat Warning until 8 PM EDT this evening for INZ009-
     017-018-024>027-032>034.
OH...Excessive Heat Warning until 8 PM EDT this evening for OHZ001-
     002-004-005-015-016-024-025.
MI...Heat Advisory until 8 PM EDT this evening for MIZ078>081-177-
     277.
MARINE...None.

&&

$$

DISCUSSION...Steinwedel
AVIATION...Roller