000
FXUS63 KIWX 170500
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
1259 AM EDT Wed Apr 17 2024

.KEY MESSAGES...

- Low confidence on strong to severe storms Wednesday afternoon into
  early evening east of I-69.

- Much cooler this weekend into early next week with some frost
  potential.

&&

.UPDATE...
Issued at 828 PM EDT Tue Apr 16 2024

Thunderstorms are entering Indiana from Illinois, in the
vicinity of a 70 knot 500-mb jet. A general weakening trend is
expected due to a marginal severe weather environment;
especially Fort Wayne and points east. Those west of Indiana 15
have a non-zero chance of small hail prior to midnight from any
of the strongest storms. While storm relative helicity is high,
so are LCLs which limit the overall tornado risk.

Dew points over Illinois are a touch higher than those of
western and central Indiana. Furthermore, observations indicate
the warm front`s northward progress has stalled from about
Benton Harbor, to Warsaw, to Fort Wayne. SPC Mesoanalysis is
handling this reasonably well. MUCAPE of 500-1,000 j/kg is
forecast to remain overnight, but become more narrow through
time. Lapse rates near 7C/km are noted upstream but are forecast
to weaken some though the night. Bulk shear remains strong. For
these reasons, a hail- producing storm cannot be ruled out but
the overall severe weather environment is marginal.

&&

.DISCUSSION...
Issued at 335 PM EDT Tue Apr 16 2024

Impressive surge of low level moisture underway as 40 kt LLJ has
remained in place all day, allowing for rapid advection of
higher dewpoints into southern parts of the area (mid to upper
50). 60+ dewpoints were not far off to the south, but strong
mixing behind the elevated warm front was keeping them in check
touching 60 in a few spots. As expected the warm front has come
through with little fanfare despite some elevated instability
and occasionally agitated cu. One shower briefly popped up over
Jay county a few hours ago and dissipated within 10 minutes.
While slgt chc pops have been maintained for collaboration, main
focus of shower/storm chances continues to take shape to our
west and south with a line of storms from SE Iowa to west of St
Louis on the main sfc warm front. The strong flow will help this
propagate NE rather quickly, possibly reaching far western
parts of the area near or shortly after 00Z. CAMs continue to
struggle with what will be left of this band of storms as it
enters, encountering a somewhat more stable environment with
loss of heating and the best flow remaining to the west. While
still somewhat skeptical on the overall setup, have maintained
categorical pops mainly western half where last vestiges of
instability will exist. Some CAMs actually dissipate the first
round and then quickly redevelop additional storms behind it
that expand as LLJ tries to ramp back up. Too many mesoscale
challenges and scenarios to make radical changes so will defer
to eve shift to monitor trends. Any precip should quickly exit
the area by 9-12Z Wed with the entire area rooted in the warm
sector of the system.

The main sfc low will be into NW Wisconsin by 12Z Wed with the
initial pre-frontal trough/occluded front racing east during
the morning hours. CAMs in general seem to agree that a narrow,
broken line of storms will develop across western parts of
Indiana roughly 14-15Z and then move east. SBCAPE will start on
the lower side 500-1000 J/KG) but increase as pockets of heating
occur ahead of the line for locations along and east of I-69.
Effective shear on the order of 35 to 40 kts will be sufficient
to help organize the storms with large hail being the main
threat. Inhibition from the overnight storms may limit the
overall development with main area of focus likely to be into NW
Ohio and points east during the afternoon. Slgt risk was
generally maintained with the best tornado risk remaining in the
NE part of the area. Once the line clears, precip will end with
a dry forecast through Thursday.

The main upper low will track just along the US/Canadian border
into Friday with the overall trough sending a cold front south
into the area with chances for showers increasing, especially
Thursday night. A few models seem to get rather aggressive on
bringing 60+ dewpoints back into SE areas, but given the limited
time for the moisture to return not buying it at this point.
This should limit any thunder potential but still warrants a
period of cat pops. Thereafter, we continue to trend colder with
highs in the 50s and lows in the mid 30s to near 40 into the
weekend. It does look like we begin to trend back towards or
above normal next week but is likely short lived as additional
waves drop south to bring more chances for showers.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1259 AM EDT Wed Apr 17 2024

Cutoff occlusion over sw MN will wobble east through the nrn lakes
today as downstream warm sector pinches off. Decaying/residual low
level moisture plume across IL likely to falter supporting any
renewed shower/storm development ahead of weakening sfc cold front
late morning (west) into mid aftn (east) and in light of continued
downward convective trends in most of the cams model suite will drop
mention with this fcst. Primary aviation issue will be strong
gradient gusts from serly this morning veering to wrly by evening
with gusts aoa 30kts likely.

&&

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

&&

$$

UPDATE...Brown
DISCUSSION...Fisher
AVIATION...T