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000
FXUS63 KIWX 171724
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
124 PM EDT Wed Apr 17 2024

.KEY MESSAGES...

- Isolated storms may redevelop this afternoon with large hail and
  damaging winds possible east of I-69.

- Showers and thunderstorms Thursday night.

- Cool and dry this weekend with highs mostly in the 50s and lows in
  the 30s. Frost possible.

&&

.UPDATE...
Issued at 1050 AM EDT Wed Apr 17 2024

Coverage of showers and isolated storms has continued to slowly
increase over the past hour, but overall updraft strengths
continue to struggle as lapse rates remain on the lower side and
convergence is rather weak. Effective shear still on the order
of 40 kts and 1000-1500 J/KG of SBCAPE still exist and should be
maintained over the next several hours with better organization
still expected as the storms approach I-69 and points east.
Grids were updated earlier to adjust to current trends and may
need some additional work as we monitor the evolution.

&&

.DISCUSSION...
Issued at 333 AM EDT Wed Apr 17 2024

A pair of upper level systems will bring 2 rounds of showers and
scattered storms to the area today. The initial round was ongoing in
an zone of isentropic lift per 305K GFS surface moving across
northern Indiana and far southern Lower Michigan at this time. SPC
mesoanalysis indicated virtually no instability. South Bend picked
up a quick >0.10" in less then 1 hour. Given the lack of shear and
no instability, do not expect any severe weather from these showers
and storms. However, the 2nd upper level system approaching from the
west will be accompanied by an occluding front. Several parameters
support the chance for severe weather, especially large hail and
damaging winds east of I-69. Bulk shear (0-6km) was already >
70kts from St Louis to Chicago per SPC mesoanalysis. Made some
major updates to lower shower/storm coverage per HRRR. The
latest HRRR favors VERY limited storm coverage today.

Otherwise, one last system will move across the area Thursday
night before cooler air and drier weather arrives for the
weekend. Severe storms should stay southwest and south of the
area given the surface low track. Rainfall amounts should be up
to half an inch and should not have major impacts on renewal of
recent flooding. At this time, frost is likely Saturday night
and Sunday night. The best chances for freezing temperatures are
near and north of the Michigan border.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 119 PM EDT Wed Apr 17 2024

Thunderstorms, producing heavy rain, are approaching KFWA. The
TSRA risk ends after this line clears.

Otherwise for the TAF period, MVFR stratus is noted upstream
across Illinois. High confidence that this builds into KSBN
over the next couple of hours. These probabilities are much
lower at KFWA, so have retained VFR ceilings there. Wind gusts
diminish this evening as the low, currently over Wisconsin,
depart to the northeast.

&&

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

&&

$$

UPDATE...Fisher
DISCUSSION...Skipper
AVIATION...Brown