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000
FXUS63 KIWX 130544
AFDIWX

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

.KEY MESSAGES...

- Very warm Sunday through Wednesday with highs well into the
  70s.

- There is a marginal risk of severe thunderstorms Sunday
  afternoon toward the Indiana and Ohio state line.

&&

.DISCUSSION...
Issued at 248 PM EDT Fri Apr 12 2024

Wind gusts have just begun topping 40mph this afternoon, with Knox
recording a 43mph gust. RAP forecast guidance suggests the surface
low and low-level wind field may strengthen yet this evening.
Decreasing cloud cover can improve our mixing, but even so, upstream
observations are closer to 40mph than 45-50 mph. So, will somewhat
hesitantly let the wind advisory ride as-is. Rain showers have
sprouted nicely off the lake and in the vicinity of vort max as seen
on water vapor imagery. This diurnal activity will end around
sunset; same for the showers noted across Wisconsin as of this
writing.

Aside from a chance of thunderstorms Sunday, a beautiful weekend is
on deck. A swirling upper-level low is replaced by high pressure
centered over the Southeast US and a ridge aloft slowly builds.
Highs near 60 on Saturday (approaching 70 toward Monticello) give
way to widespread 70s Sunday. However, a low streaking through the
Great Lakes will send a weak cold front through in the afternoon.
This will result in plummeting temperatures lakeside as
northwesterly wind sets in. This cold front could be the focus for
isolated thunderstorms toward the IN-OH state line. Here,
instability is marginal (near 500-1,000 j/kg), but dew points in the
upper 50s and shear near 40-50 knots are appropriate for the
highlighted marginal risk. Forecast soundings show a cap near 5,000
ft; something the cold front might overcome. I`ll hold steady with
only a 20% chance or so due to very limited coverage on forecast
guidance.

This is a weak cold front indeed as high temperatures quickly
rebound Monday back into the 70s. This, as 500mb heights rise in
response to a deepening trough over the west. By midweek, a surface
low moves through the Midwest bringing more rainfall and a risk of
severe weather to Illinois and western Indiana. Forecast rainfall
ranges notably at this time.

In the wake of this low, a second is quickly on its heels to end the
week. This brings notably colder air to the region; a real bummer
following a week in the 70s.

&&

.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...Marsili
AVIATION...AGD