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000
FXUS63 KIWX 130821
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
421 AM EDT Sat Apr 13 2024

.KEY MESSAGES...

- Potential for heavy rainfall this upcoming week to once again
  aggravate ongoing river flooding with several chances for
  showers and storms in a very moist environment.

- Chances for thunderstorms at times Sunday through Thursday to include
  a marginal risk of severe thunderstorms Sunday afternoon and
  another severe risk Tuesday.

- Warm Sunday through Wednesday with highs in the 70s. Turning
  much colder late in the week with a good chance of
  temperatures near freezing this upcoming weekend.

&&

.DISCUSSION...
Issued at 310 AM EDT Sat Apr 13 2024

The powerful low that caused the strong winds yesterday was
occluding and filling near James Bay. A surface ridge axis well
to the southwest of the low was west of the area and will move
east with winds over the forecast area backing to the southwest
by this evening. A weak upper level system with approach the
area Sunday in tandem with an elevated mixed layer (EML). A
substantial/steep 700mb/500mb lapse rate close to 8.5C/Km will
provide an environment for stronger storms; however, maximum
CAPES generally should only be 1.0K to 1.5K J/Kg. Fairly strong
capping may completely inhibit storm development as indicated by
several CAMS and some of the spectral models.

For Monday into Thursday, it looks like the storm mode will
evolve into more of a heavy rain threat with tall by thin CAPEs
and high precipitable water values. The only exception is late
Tuesday into Tuesday night with a strong negatively tilted trof
moving into the forecast area. SPC has maintained a 15% severe
risk for the "old" Day 5 at this time. Current thinking is with
ongoing flood issues, addition rainfall that may become locally
heavy with any training will aggravate the current situation.
Otherwise, it looks like a pattern change to cooler and drier
weather will begin late with week with as a longwave trof axis
sets up over east North America. Temperatures may drop to
freezing this coming weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 138 AM EDT Sat Apr 13 2024

VFR conditions are expected to persist through this forecast
period.

The southern Great Lakes will be positioned in upper level
inflection zone to begin this period between broad low amplitude
upstream ridging across central CONUS and longwave troughing
across eastern CONUS. West-northwest winds will persist into
this afternoon due to position of upstream low level ridge axis
across northeast IL/northwest IN. The strongest low level height
gradient will persist along/east Interstate 69 with some gusts
to around 20 knots expected at KFWA through early-mid afternoon.
By late this afternoon, strength of low level warm advection
will increase which could lower mixing heights a bit. This
evolution and approach of low level ridge axis should cause a
quick drop off in gusts after 22Z. A decent southerly low level
gradient will develop tonight as the ridge pushes to the east.
This could give rise to some marginal LLWS criteria conditions
by the 03Z-06Z timeframe at KSBN and after 06Z at KFWA. Will
address this potential in more detail with the 12Z TAFs.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...Small Craft Advisory until 5 AM EDT early this morning for
     LMZ043-046.

&&

$$

DISCUSSION...Skipper
AVIATION...Marsili