964
FXUS63 KIWX 200625
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
225 AM EDT Thu Jun 20 2024

.KEY MESSAGES...

* There is the potential for isolated strong to severe storms this
  afternoon into early this evening in northwest Ohio, northeast
  Indiana and south-central Michigan. Damaging winds appear to be
  the primary threat.

* Hot, humid and mainly dry conditions are expected through
  Saturday. Peak afternoon heat indices will approach 100
  degrees in many locations, hazardous to sensitive and
  vulnerable groups.

&&

.DISCUSSION...
Issued at 223 PM EDT Wed Jun 19 2024

Gulf of Mexico moisture streaming north on the western fringe of a
persistent Mid Atlantic centered upper ridge has kept mid-high
clouds and even a few showers/storms around so far today.
Similar to yesterday, this has provided some relief from the
heat/humidity, though satellite and model trends favor a trend
toward a partly cloudy skies and heat indices into the 90s this
afternoon. Isolated to scattered showers and storms will be the
focus otherwise this afternoon into early this evening, especially
along and east of I-69 where a mid level shear/moisture axis
and area of subtle convergence in the low levels linger. Lacking
shear and forcing will once again limit storm coverage/chances,
but juicy airmass and DCAPE values near 1000 j/kg suggest that
a collapsing pulse storm could produce a localized downburst.

Drier sinking air does advect into the area into Thursday and Friday
as the strong Mid Atlantic upper ridge retrogrades west-
southwest into the OH and Mid MS Valley. This process should
force the primary moisture channel to the west and north during
this time with less cloud cover and higher probabilities of
experiencing peak PM heat indices near 100F. Subtle shortwaves
and weak sfc outflows/lake breezes could be enough to activate
isolated convection during the afternoon hours each day
(20-30%), mainly north of US 30, with most locations remaining
dry/hot.

For the weekend, an upper level trough and associated sfc reflection
will release east-southeast through the Upper Midwest and Great
Lakes. The local area will no doubt be in the breezy and hot warm
sector on Saturday in advance of the approaching system, though
cannot completely rule out a few late day storms if any pre-frontal
features sag south into this unstable and humid airmass. The heat
will remain the story otherwise on Saturday with headlines
potentially needing expansion at some point. The primary cold front
and best opportunity for more organized rain/storms is still favored
late Saturday night through early Sunday afternoon, though
differences in moisture quality and timing remain within 12z
guidance.

A brief respite from the heat and humidity remains in the cards post-
frontal into Sunday night and Monday with temperatures more common
for late June. The southern Great Lakes then look to become
positioned on the northeastern fringe of a building upper ridge
by Tuesday and Wednesday with ring of figure type convective
systems in the vicinity.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 159 AM EDT Thu Jun 20 2024

Showers and storms have nearly all dissipated with the loss of
daytime heating. A weak front was drifting south into far
northern Indiana and had become more diffuse. The front was
draped just south of the Michigan border. Latest model guidance
favors the front becoming stationary over the area. Given the
diurnal flare to convection with the front in the vicinity later
this afternoon and evening, have placed a VCNTY TS at SBN.
Otherwise, VFR conditions will prevail.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Saturday for
     INZ005>008-012>015-020-022-023-103-104-116-203-204-216.
     Excessive Heat Warning until 8 PM EDT Saturday for INZ009-017-
     018-024>027-032>034.
     Air Quality Alert until midnight EDT /11 PM CDT/ tonight for
     INZ020-103-203.
OH...Excessive Heat Warning until 8 PM EDT Saturday for OHZ001-002-
     004-005-015-016-024-025.
MI...Heat Advisory until 8 PM EDT Saturday for MIZ078>081-177-277.
MARINE...None.

&&

$$

DISCUSSION...Steinwedel
AVIATION...Skipper