562
FXUS63 KIWX 031939
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
339 PM EDT Thu Apr 3 2025

.KEY MESSAGES...

- There is a chance of rain (40-60%) tonight, primarily south of
  US 24.

- Dry to begin Friday followed by an increasing chance of rain
  from south to north.

- A period of heavy rain is expected Friday night through
  Saturday which will worsen any ongoing flooding.

&&

.DISCUSSION...
Issued at 336 PM EDT Thu Apr 3 2025

A broad trough is centered over the Four Corners while a surface low
is taking shape over the mid-Mississippi River Valley. Warm air
advection is underway and is promoting a slowly blossoming
precipitation shield across IL and IN. Cross sections depict a
notable dry layer from 925mb to 700mb which will result in virga for
the next few hours until saturation can occur, aided in part by
improving 500mb jet dynamics. Overall this evening and tonight, a
glancing blow of rain to those south of US 24 while the axis of
heavy rain is focused toward the central part of Indiana.

The western US trough sharpens through Friday and Saturday in
response to an upstream ridge moving inland of the West Coast. This
results in the heavy rain axis lifting further north into our
forecast area. Friday begins dry but rain arrives from south to
north through the day. The SPC has a sliver of our far southern
counties in a marginal risk for severe weather. The HREF indicates a
colocation of sub-500 j/kg MUCAPE and 60 knots of shear. Soundings
are otherwise severely capped but could be cold enough to support
hail from the strongest cores. Primary window of opportunity would
be about 8p to 2am EDT Friday/Saturday. Confidence in severe weather
occurring is low.

A period of heavy rain is anticipated Friday night through Saturday
morning. The placement of the deformation zone is still in question
(with the NAM notably north). Such a northern solution could require
additional counties to be added to the flood watch. Trends will need
to be monitored closely among incoming high resolution guidance. The
current forecast calls for about 2 to 3 inches of rain within the
watch area, tapering off toward 1 inch in adjacent areas. This will
certainly result in additional rises on area waterways. Drying out
Sunday morning.

Sharply colder by Monday afternoon as a stout and anomalous cold
air mass blasts into the Great Lakes. Rain and then ultimately snow
showers are expected along and in the wake of this front. Cold
temperatures linger through Tuesday, followed by moderation as the
trough moves east.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1213 PM EDT Thu Apr 3 2025

VFR conditions are anticipated through the TAF period despite
increasing clouds. Departing low pressure over the far northern
Great Lakes is still promoting locally gusty winds as of this
writing. The gradient will ease and low-level mixing will be
reduced via increased clouds as well over the coming hours
resulting in a reduction of wind gusts.

A thermal gradient will bisect Indiana overnight and could bring
a glancing blow of some showers to KFWA after 03z. A mid-layer
dry wedge persists and guidance is generally split on precip
chances. Therefore, will hedge once more on the dry side for
consistency. Wind veers through the TAF period in response to
the combination of the aformentioned departing low and a low
approaching KSTL late.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through Sunday morning for INZ009-017-018-020-
     022>027-032>034.
OH...Flood Watch through Sunday morning for OHZ001-002-004-005-015-
     016-024-025.
MI...None.
MARINE...None.

&&

$$

DISCUSSION...Brown
AVIATION...Brown