183
FXUS63 KIWX 241813
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
213 PM EDT Fri May 24 2024

.KEY MESSAGES...

- Shower and thunderstorms return this afternoon, moreso this
  evening, with severe storms possible, mainly west of Indiana
  15/US 131.

- Greater chances for showers and thunderstorms Sunday
  afternoon and night with both severe storms and possibly heavy
  rain/hydro issues existing.

- Lingering showers may impact activities on Memorial Day and
  Tuesday.

&&

.DISCUSSION...
Issued at 210 PM EDT Fri May 24 2024

A low pressure system moving through the Midwest today is expected
to bring thunderstorms to the area this afternoon and evening. A
line of storms currently moving through northern Illinois could
reach the western extent of our forecast area as early as 3 pm.
However, isolated storms are beginning to pop up ahead of this line,
in the vicinity of a warm front draped from Berrien County southeast
through Allen County and into Ohio. This will lift slowly northward
this afternoon, and sfc CAPE will increase to over 2000 J/kg with
dewpoints rising into the 60s. Yet bulk shear is marginal at only
around 25-30 kts, so main threat will be strong outflow winds. High-
res models have not done a very good job capturing the ongoing
convection, so confidence is low in the exact timing and location of
storms, but still think the best chances for rain will be between 8
pm and 4 am when the cold front pushes in. The front will still be
over the area Saturday morning with lingering showers, but as it
makes its way east, drier air under northwesterly flow will dominate
through Saturday night.

Another low pressure system will arrive on Sunday afternoon with
more showers and thunderstorms. This has a better chance of severe
weather with NAM sfc CAPE up to 4000 J/kg and bulk shear 50+ kts.
There is also a greater threat for heavy rain on Sunday evening with
precipitable water increasing to around 2 inches. Rain may be slow
to move east Monday morning, but by Memorial Day evening, most
locations should be dry. It will also be much cooler behind this
system with highs only in the low 70s and breezy winds.

Large scale troughing over the eastern half of the US means that
unsettled weather will continue on Tuesday. On Wednesday, high
pressure will build over the plains, and drier conditions will
return, though it will remain cool. It will stay dry on Thursday,
but warm a bit as the ridge shifts east.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1253 PM EDT Fri May 24 2024

A decaying line of thunderstorms is approaching the Indiana
state line at this time. Wind gusts of 20 knots have been
observed with frequent lightning within the strongest, discrete,
cells. Medium-high confidence -TSRA will be recorded at KSBN
this afternoon as the enrvionement remains generally favorable.
Moreso, while satellite trends have diminished, the thunderstorm
line its self remains balanced on radar; meaning, it is not yet
outflow dominant which would otherwise indicate immediate decay
of the line.

Beyond 00z the forecast is murky and I therefore stayed close to
the inherited TAFs. Thunderstorms are expected to redevelop over
Iowa and Missouri this afternoon, evolving into a bowing line
of thunderstorms to race through Indiana. Confidence is low on
this solution due to the existing thunderstorms complex in
place, which is not being modeled well. Observations over said
states remain favorable for thunderstorms development ahead of
the cold front. Thus, a severe thunderstorm risk remains on the
table tonight.

One additional solution to note would be discrete thunderstorms
developing almost immediately in the wake of this current
thunderstorm cluster. This seems somewhat less likely based on
what would be a very limited recovery period.

Lastly, should heavy rain materialize, there is a non-zero
chance of BR/FG prior to sunrise. This was retained at KSBN
where -TSRA is perhaps more likely when compared to KFWA.

&&

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

&&

$$

DISCUSSION...Cobb
AVIATION...Brown