034
FXUS63 KIWX 131902
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
302 PM EDT Mon May 13 2024

.KEY MESSAGES...

- Scattered thunderstorms this evening, decreasing in coverage
  overnight.

- Showers and storms dot the area Tuesday. Drying out Wednesday.

- Remaining mild through the week.

&&

.DISCUSSION...
Issued at 259 PM EDT Mon May 13 2024

The latest high-resolution guidance has lead me to reduce POPs and
rainfall forecast amounts for the next 24 hours. As hinted in this
space over the weekend, poleward moisture transport is poor as of
this writing. This is in part due to ongoing convection across the
south, but moreso a notable dryslot is evident on mid-and-low-level
water vapor this afternoon. Despite this, a few thunderstorms are
starting to emerge over Illinois and far western Indiana associated
with an 850mb thermal gradient and a vorticity maximum on the nose
of the dryslot. Instability and lapse rates will be sufficient to
support scattered thunderstorms for the remainder of the afternoon.
Inverted-V soundings depict a non-zero damaging wind gust threat.
However, a lack of wind shear will limit the longevity and
organization of thunderstorms.

Overnight, showers and thunderstorms are anticipated to decrease
in coverage. This is likely due to the loss of daytime heating
and the aformentioned thermal gradient having moved north. In
fact, there should be several dry hours overnight. However, a
secondary vort maximum lifts in through central Indiana prior to
sunrise, renewing the coverage of showers and storms. This is a
period that will need to be monitored by the evening shift for
further adjustment.

Through Tuesday, moisture advection improves from the Atlantic,
resulting in numerous showers and some thunderstorms during the day.
This activity tapers off late Tuesday night as the low crosses the
Appalachians. Forecast rainfall tonight through Tuesday is now
closer to 0.50" than the previously advertised 1".

Gradually drying out after sunrise Wednesday, but an active upper-
air pattern remains such that showers and storms return later
Thursday and linger at times into Saturday. Forecast guidance is
rather noisy Thursday and beyond, resulting in only minor
adjustments to the in-house blend of POPs. A strengthening ridge
across the south hits at 80-degree temperatures this weekend
into early next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 123 PM EDT Mon May 13 2024

Steep lapse rates and influx of elevated moisture has resulted
in an expanding cu field across mainly western IN back into IL.
Handful of cells have managed to gain some strength and even
produce some lightning, but weak shear is setting the stage for
rather pulsy storms that are difficult to capture in TAFs. KSBN
seems to be in the favored path of development, resulting in a
continuation of a tempo group for thunder with mainly brief MVFR
vsbys. Will need to monitor trends prior to 00Z for possible
ramp up to more of a predominate forecast for the activity.
Leaving KFWA dry for now through 00Z, but will monitor trends as
well.

Past 00Z, better coverage should begin to materialize across
the area with tempo thunder at KSBN maybe more questionable
given loss of heating and potential that any storms this
afternoon could reduce instability and limit lightning. No
changes for now.

Confidence is not overly high on how low cigs will drop late
tonight into Tuesday or if showers will last beyond 8 or 9Z.
Minor tweaks made but will let later forecasts hone in on
things.

&&

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

&&

$$

DISCUSSION...Brown
AVIATION...Fisher