205
FXUS63 KIWX 240523
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
123 AM EDT Tue Sep 24 2024

.KEY MESSAGES...

- Rain showers will expand in coverage overnight with greatest
  coverage expected across northeast Indiana and northwest Ohio
  late night.

- Scattered showers and storms expected later Tuesday
  afternoon/early Tuesday evening. An isolated strong to severe
  thunderstorm is possible.

- Dry midweek before a low chance (20-30%) of showers late this
  week into the weekend.

&&

.UPDATE...
Issued at 900 PM EDT Mon Sep 23 2024

Low level winds have backed this evening in response to
emergence of next upstream mid/upper level trough across the
Central Plains. This has allowed for some strengthening of
advective forcing as low level theta-e gradient from central IL
to central IN has started a retreat back northward. Showers
south of the US-24 corridor this evening should remain on the
light side with little support for more organized synoptic lift
behind this advective forcing. A more focused area of stronger
showers/embedded storms has developed across eastern
MO/southwest IL this evening. This appears to be at the nose of
a 90 knot upper jet streak sampled by KOUN 00Z RAOB data. The
left exit region of this upper jet streak will continue to
migrate across the Ohio River Valley into early Tuesday morning.

Another area of forcing to monitor for the overnight may be
tied more to a maturing 900-800 mb circulation across central
IL as the Central Plains upper level wave lifts northeast. This
low level frontogenetic flow may support enhancement to showers
from central IL into NW IN/SW MI late tonight/early Tuesday.
Best rainfall rates overnight into early Tuesday are still
expected in association with more pronounced upper jet forcing,
which should also be co-located with some strengthening low
level moisture convergence from central IN into northwest OH via
a modest southerly low level jet. Additional refinement to PoPs
will certainly be needed as these sharper forcing areas evolve
overnight, but previous forecasted trends to likely/categorical
PoPs still seem in order.

&&

.DISCUSSION...
Issued at 125 PM EDT Mon Sep 23 2024

Abundant cloud cover today has effectively kept temperatures
down. Most locations will only see highs in the 60s, although a
few may get up to around 70 degrees.

A low pressure system currently centered over Arkansas and
Missouri will make its way northeastward this evening. Showers
could begin moving into southwest portions of the forecast area
as early as 6-7 pm EDT. While isolated thunder is possible,
chances are slim due to a lack of instability. Showers will
continue through the night, mainly south of US 24. Then as the
low tracks farther northeast by daybreak, shower activity will
also shift northward. The surface low will cross the region
from southwest to northeast (White County, IN to Williams and
Fulton counties in Ohio) on Tuesday afternoon. In its vicinity
and in the warm sector to the southeast will be the best chances
for thunderstorms. It is in this area where bulk shear will be
30-40 kts and CAPE in excess of 1500 J/kg that SPC has extended
the Marginal Risk for severe storms from around 3 pm through 9
pm. Damaging wind or hail could be possible, or even an isolated
tornado.

Wednesday will be mostly dry, but a few lingering showers may
still be possible as the upper trough crosses the Great Lakes.
On Thursday and Friday, the region will again be stuck between
low pressure systems and high pressure will build back in.
It will be dry and temperatures will warm, although it will not
be as hot as last week, with highs confined mainly to the upper
70s or low 80s. Model uncertainty comes into play for the
weekend concerning the position of an upper low to the
southwest and a tropical system near the west coast of Florida.
Consensus is that we should see more rain by Sunday into Monday.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 123 AM EDT Tue Sep 24 2024

Surface low pressure will move into the area today with multiple
round of showers expected. Ceilings will steadily lower through
the early morning as this system approaches. IFR ceilings
already at KSBN with some brief LIFR possible around 12Z. KFWA
will take a bit more time to drop given more dry air entrainment
but IFR is likely here as well by around 12Z. Some improvement
expected with diurnal mixing especially at KFWA where low track
may favor much better mix out. IFR returns behind the low
Tuesday night though. There is some chance of thunder
(especially at KFWA) but confidence in timing and coverage
remains very low at this point.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...None.
OH...None.
MI...None.
MARINE...None.

&&

$$

UPDATE...Marsili
DISCUSSION...Cobb
AVIATION...AGD