436
FXUS63 KIWX 241702
AFDIWX

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

.KEY MESSAGES...

- Driest periods of the holiday weekend look to be through this
  afternoon and again Saturday through early Sunday.

- Shower and thunderstorm chances return this afternoon, moreso
  this evening, with severe storms possible 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 253 AM EDT Fri May 24 2024

Unfortunately, this holiday weekend period there will be
several active weather periods into next week beginning later
today. A low pressure system currently over the Dakotas will
move northeastward into Minnesota and an associated warm front
draped southeastward will move northward into the CWA today.
This will allow for a moistening of the air with dew points
getting back into the 60s once again. Highs today will be in the
low to mid 80s. Surface based CAPE values this afternoon will
approach 1500-2000 J/kg along with bulk shear values around
25-35 knots. This will set- up the atmosphere for some
convection that will be focused around a cold front further west
which will already have thunderstorms going earlier this
afternoon.

Expectation is around 18-19z the cold front and the accompanying
thunderstorms will be at the Mississippi river and should start
to enter our western parts of the CWA around 22z. A more
isolated coverage of thunderstorms will occur and then should
increase in coverage as the front gets closer. There is still
some questions on how strong the storms will be once they arrive
with the later timing and also with a more organized area of
convection that may push further north over Lake Michigan.
Latest HRRR guidance suggests an MCV develops over northern IL
and heads northeastward with scattered thunderstorms building
southward over our CWA. However, with the aforementioned
instability and sufficient shear over the area would not be
surprised for some of the thunderstorms to become strong to
severe. The main threats as of now looks to be wind and somewhat
less so being hail. Further west into northern IL the SPC does
have a 5% tornado probability and around a 2% area for the far
western parts of northern IN. SPC also still has mainly the
western portions of our area under a slight risk and further
eastern sections as marginal for severe storms. The cold front
should push through most of the area after 12z on Saturday
however a few remaining showers and thunderstorms will be
possible into Saturday afternoon for mainly east of I-69.

Once the cold front moves through on Saturday clearing skies
will be left in it`s wake and slightly cooler and more
comfortable airmass. Highs will be in the lower 70s closer to
the lake and upper 70s to low 80s for areas further south and
east. This will be the better part weather wise of the holiday
weekend and will continue into early Sunday morning. Another
developing low over the Plains will then move northeastward and
pass just northwest of the area but will bring another
rinse/repeat scenario with a warm front on Sunday morning
increasing clouds and chances of showers along with a slug of
moisture with dew points getting into the mid to upper 60s.
Highs will also warm back into the upper 70s and low 80s.
Another cold front will then move through Sunday evening
bringing another chance of strong to severe thunderstorms. SPC
currently has Sunday marked with a 15% chance of severe storms.

Lingering showers and a few thunderstorms will continue for
Memorial Day into Tuesday. Temperatures will be cooler both days
with highs each day in the lower 70s with northern parts of the
CWA struggling to get out of the 60s. The next break in
precipitation chances look to come by Wednesday into Thursday
with broad ridging moving into the center of the CONUS which
will bring a warming trend into the end of next week.

&&

.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...Andersen
AVIATION...Brown