414
FXUS63 KIWX 231801
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
201 PM EDT Sun Jun 23 2024

.KEY MESSAGES...

* Showers and storms diminish this morning with widely
  scattered showers and isolated storms possible through early
  afternoon along a cool front.

* Seasonable temperatures and less humid conditions from today
  into Monday, but heat and humidity may return for Tuesday.
  Chances of storms/cloud cover lead to low confidence in
  maximum heat indices for Tuesday.

* Renewed chances of thunderstorms for Tuesday and Wednesday. Some
  of these storms could be strong to severe, but a good deal of
  uncertainty remains with timing and extent of the severe threat.

&&

.DISCUSSION...
Issued at 425 AM EDT Sun Jun 23 2024

Widespread showers and thunderstorms in pre-frontal environment
have been exhibiting signs of a weakening trend over the past
hour, which should continue through the rest of the early
morning hours. Effective shear on the order of 35 knots will
support maintenance of this convection into northwest Ohio, but
in a continued weakening state as this convective line has
outrun better MUCAPE axis. A few gusts in excess of 30-35 mph
will be possible through 10-11Z with some brief heavy
downpours. Progression of this line should not lead to any
notable hydro concerns however. A lagging mid/upper trough
working across the western Great Lakes this morning, will allow
a region of weak positive vorticity advection to spread across
the southern Great Lakes and Ohio Valley through early
afternoon. Main question for this afternoon will be on magnitude
of instability along the cold front as it progresses through
southeast half of the area. Extensive debris cloudiness
gradually diminishing this morning may slow destabilization
given early afternoon frontal timing, but some low level
moisture pooling could briefly allow a modest axis of surface
based CAPE to push back across southeast third of the area by
midday. Will maintain scattered PoPs across the southeast
through early afternoon for some regeneration of showers and
thunderstorms, with thunder potential much less across northwest
half of the area based on frontal timing.

Influx of drier low level air today into this evening will allow for
noticeably cooler conditions tonight with lows in the lower 60s and
perhaps upper 50s across the northeast. Sfc anticyclone will provide
quiet conditions tonight into Monday evening. Monday will feature
seasonable temperatures and low humidity values.

Tuesday and Wednesday still appear to be potentially more active
days in terms of renewed convective chances. Departure of low
level anticyclone Monday night into early Tuesday will allow a
very sharp low/mid level theta-e gradient to shift back east
across the Great Lakes and Ohio Valley. Potential does exist for
warm/moist advection to allow area to push near heat advisory
criteria again by Tuesday afternoon, but increasing potential of
convection still casts a large shadow of uncertainty on how
this will evolve.

In terms of late Monday/Tuesday`s convective potential, stronger
synoptic upper level wave will remain well displaced to the
north across Manitoba with zone of strong moisture transport
lifting north across the Upper Midwest. Strong low level
moisture convergence ahead of associated cold frontal boundary
should allow for overnight convection to develop across the
Upper MS Valley/northern Great Lakes into Tuesday morning.
Farther south across the local area, some risk of isolated
convection may accompany the warm/moist advection with the warm
frontal zone, but confidence in convection through early morning
Tuesday is low due to potential of capped conditions. While
moderate to strong instability may develop across the southern
Great Lakes and Ohio Valley on Tuesday, ingredients for
convection remain muddled at this forecast distance with a wide
range of possibilities persisting regarding the evolution of
potential upstream convectively enhanced mid level disturbance
approaching the area. Overall synoptic shear profiles look to
be not overly impressive, but if convective disturbance affects
the area it could have its own enhanced shear associated with
it. Larger scale signals do appear to be somewhat favorable for
MCS type development across the region with stronger upstream
northwest flow aloft and potential strong instability gradient
sprawled across the area. Some medium range guidance does
suggest potential upwind development with southwesterly low
level jet feeding in from the southern/central Plains which
could possibly keep greatest severe risk across the Mid MS
Valley. Needless to say plenty of uncertainty in this scenario,
but Tuesday/Tuesday night will be a period to watch for a round
or two of convection. SPC has placed much of northwest half of
the forecast area in a Day 3 Slight Risk of severe storms.

Another southeast diving short wave is expected on Wednesday with
main cold front pushing through the area that could bring additional
chances of storms. A transition to drier and slightly cooler
conditions is expected for Thursday, but in this highly progressive
pattern, mid/upper level heights build back in quickly for
Friday/Saturday before next potential fropa for the weekend. Did
maintain low PoPs next weekend to account for this.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 120 PM EDT Sun Jun 23 2024

The weak cold front has moved southeast of FWA with ample post-
frontal low clouds and lingering light precipitation well behind
the cold front over northern Indiana. Made some adjustments for
more persistent clouds and light precipitation based on
satellite, surface & radar obs & trends. It looks like the HRRR
and RAP have initialized this activity reasonably well. Clouds
should decrease and winds should become light by late evening.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Beach Hazards Statement until 5 PM CDT this afternoon for
     INZ103.
OH...None.
MI...Beach Hazards Statement until 6 PM EDT this evening for MIZ177-
     277.
MARINE...Small Craft Advisory until 6 PM EDT this evening for LMZ043-
     046.

&&

$$

DISCUSSION...Marsili
AVIATION...Skipper