153
FXUS63 KIWX 221504
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1104 AM EDT Wed May 22 2024

.KEY MESSAGES...

- While a brief shower or storm cannot be ruled out in far
  northeast Indiana and northwest Ohio through early afternoon,
  dry conditions will most likely dominate the rest of the day.

- Less humid conditions overspread the area later today into
  tonight.

- Periodic chances of showers and thunderstorms for much of the
  long term period, especially Friday and Sunday.

&&

.UPDATE...
Issued at 1104 AM EDT Wed May 22 2024

Pre-frontal trough was making steady progress east, with the
back edge (Wabash to Sturgis) clearly defined by the strong
subsidence (lack of clouds) and slow drop in dewpoints. Low 60
dewpoints remain ahead of the trough with SPC Mesoanalysis
showing 1500-2000 J/KG SBCAPE with 30-35 kts of effective shear.
While we would be normally entering a favorable window for some
showers and storms along this feature, a lack of sfc
convergence is depicted on sfc obs and the best mid/upper level
dynamics are well north or SE of the area. While a stray
shower or storm could pop from Jay to Allen Co OH in the next
couple of hours, all signs point towards reducing pops. Also,
the 13Z SPC DY1 outlook trimmed the marginal risk nearly out of
our forecast area (still existing along the rough are noted
above).

Rest of the forecast on track otherwise.

&&

.DISCUSSION...
Issued at 350 AM EDT Wed May 22 2024

Focus for today`s forecast will be additional chances of storms with
a few showers and storms this morning, and a potential of an
isolated storm later this afternoon into this evening across the far
southeast.

Small pockets of showers and isolated thunderstorms are ongoing this
morning from southeast Illinois into south central Indiana. These
showers and storms appear to have formed in left exit region of a 90
knot upper jet streak approaching from the southwest. Would expect
these showers to track across southeast third of the area this
morning, with a few stronger sub-severe gusts possible. A secondary
area to possibly watch for isolated development is along cool
front working its way across northeast Illinois. Some pooled low
level moisture could be just enough to overcome stubborn weak
cap for an isolated shower or thunderstorm as it works across
the area later this morning into early afternoon. It does appear
a lull in these rain chances will develop this afternoon as
better pooled moisture shifts east of the area, and weak capping
lingers. Some uncertainty this afternoon whether isolated
convection may focus along the cold frontal boundary, or
possibly immediately downstream near weak pre-frontal trough
feature that could have slightly better low level moisture to
overcome a weak cap. If the pre-frontal area is favored, any
isolated convection would likely focus just east-southeast of
the local area this afternoon. A decent westerly flow regime
will persist today, and while better shear profiles are post-
frontal, the cold front/pre-frontal zones should have 35-40
knots of deep layer shear and moderate instability to work with.
However, with secondary upper trough still upstream and
shearing out across NW IL/E IA, confidence in developing this
isolated convection across the far southeast is on the low side
given what should be fairly weak frontal/pre-frontal convergence
fields. If convection is able to develop this afternoon, cannot
rule out an isolated stronger storm across the far southeast.

Good low level mixing will result in breezy conditions today,
with strongest gusts across the far southeast where warmest sfc
temps into the low to mid 80s are expected. High closer to the
lakeshore may only reach around 70 behind the cool front.

For tonight, it is possible some low coverage showers and storms
develop south of US 24 with perhaps some response to the weak
mid/upper level forcing with the wave shearing out across the
southern Great Lakes. However, waning instability by this time
should preclude a severe threat. Dry weather is expected overnight
with noticeably cooler and less humid conditions.

For Thursday, low level theta-e gradient will stall out across far
southern portions of the forecast area. A low level anticyclone will
begin to depart the area setting up a weak southerly return flow
regime. This could interact with this moisture gradient for a low
end chance of an isolated shower, but confidence in measurable
precip continues to diminish Thursday and have confined slight
chance mention to far south/southeast.

The next upper level short wave of note for local area should
be the negative upper height anomaly working across the Pacific
Northwest this morning. Guidance is in reasonable agreement in
favored track of this wave bypassing the area across the Upper
Midwest, with the disturbance eventually reaching southern
Manitoba late Friday. It does appear the Great Lakes upper
ridge will be a bit stubborn once again to break down which
would delay next fropa until Friday evening with the best chance
of showers and storms. Portions of local area have been placed
in Day 3 Marginal Risk of severe storms. Limiting factors to
isolated severe weather appear to be possible later timing of
best chances of storms and shear limitations given potential of
Great Lakes mid/upper level ridging to be stubborn to break
down.

The first half of the weekend should feature primarily dry
conditions in wake of Friday`s system, but pattern looks to remain
active for latter parts of the holiday weekend as a fast moving
eastern Pacific wave cuts across central CONUS into the Mid MS Rvr
Valley by early Sunday. This could be a period to watch for stronger
storms, but a good deal of uncertainty exists with how far north sfc
reflection will make it. It is possible a decent instability
gradient could be sprawled across the Ohio River Valley on
Sunday. There does appear to at least be a good signal for
precip for Sunday/Sunday night however. A modest shot of cooler
air should filter back in for Monday/Tuesday with some scattered
showers possibly lingering with indications of broad cyclonic
flow across the Great Lakes.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 549 AM EDT Wed May 22 2024

On satellite, a band of stratocumulus clouds can be seen
entering Indiana as of 10Z. Ceilings may drop as low as 3500 ft
this morning, but should remain VFR. Southerly winds will be
gusty this morning and afternoon with gusts 25 to 30 kts
possible. Winds become westerly after sunset tonight and
diminish to 5 to 10 kts. Dry conditions and VFR ceilings prevail
throughout much of today.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ043-
     046.

&&

$$

UPDATE...Fisher
DISCUSSION...Marsili
AVIATION...Johnson