615
FXUS63 KIWX 140121
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
921 PM EDT Fri Jun 13 2025

.KEY MESSAGES...

- Numerous showers move through overnight with an isolated
  thunderstorm possible prior to sunset. Rain may be heavy at
  times.

- Rain gradually ends from west to east on Saturday.

- Becoming very warm by Monday and Tuesday with highs well into
  the 80s.

&&

.UPDATE...
Issued at 920 PM EDT Fri Jun 13 2025

No major changes to the going forecast this evening, with the
immediate forecast concern late this evening into the overnight
hours focusing on heavy rain potential. KIND VAD wind profile
has been indicating a subtle increase in low level winds this
evening with a 20 knot southerly jet at 5k feet. Speed
convergence with this weak feature appears to have aided a few
stronger cores earlier this evening across central Indiana.
These stronger showers have generally weakened through time
however. Going into the overnight hours, near term higher res
guidance does suggest that a 925-850mb trough feature will
sharpen from east central Illinois into extreme northwest Ohio
as the upstream southern latitude upper level short wave trough
slowly lifts northeast into pre-existing southern Great Lakes
deformation zone. This trough axis will likely serve as a focal
point for additional slow moving showers and perhaps a
thunderstorm overnight. Guidance consensus almost seems to be
highlighting two distinct areas for heavier rainfall potential
overnight, one roughly along the US 24 corridor where low level
convergence is maximized along the sharpening low level trough
axis, and perhaps another area across northwest corner of Ohio
where a secondary max in low level moisture convergence is
possible due to some directional wind convergence.

There are plenty of factors that would support at least
isolated instances of heavy rainfall including warm cloud depths
to around 12k feet, PWATS near max climo levels of 1.8 inches,
and stationary nature to developing SW to NE oriented low level
trough. Still a good deal of uncertainty as to where heaviest
rain axis will set up, but feel a good first approximation would
be near US 24 corridor across far NE IN/NW OH into the early
morning hours Saturday.

&&

.DISCUSSION...
Issued at 318 PM EDT Fri Jun 13 2025

A picturesque mid-latituade cyclone is evident on water vapor
this afternoon, swirling over the greater St. Louis area.
Anomalous moisture has streamed into the area with both a Gulf
and Atlantic moisture connection. The result is a period of
steady rain moving northward through Indiana. Lightning has
been sparse thus far, but a few taller cores are popping along
the IN-OH line. Moisture-rich soundings will limit the severe
weather threat to primarily pea-size hail for the tallest cores.
Instead, through Saturday morning, locally heavy rainfall is
the primary concern. South of Michigan, a deformation zone is
anticipated to take shape and given the anomalous moisture, weak
flow, and enhanced lift from a strengthening low-level jet, a
narrow area could see rain totals approaching 2 inches. The
location of this is uncertain, but lingering high pressure over
the Upper Great Lakes will generally favor the heaviest rain
south of the Michigan state line. Rain tapers off from west to
east through Saturday, but lingers well into the afternoon for
those near Portland and Lima.

As mentioned in the preceding discussion, primarily dry Sunday
through Monday but cannot completely rule out a stray pop-up storm
amid active zonal flow through the Great Lakes. Very warm as well
with rising 500-mb heights resulting in highs well into the 80s
by Tuesday. A shortwave moves through the upper Great Lakes
Tuesday brings an increased chance of showers and storms. A
second, more potent, wave moves through Wednesday. This will
bring the best opportunity for widespread thunderstorms. Nothing
is set is stone, but we`ll need to monitor the risk of severe
storms with this wave. Cooler in the wake of this trough as
northwest flow is established briefly.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 750 PM EDT Fri Jun 13 2025

A slow moving upper trough will continue to try and lift
northeast before getting injected into primary weak belt of
westerly flow aloft. This evolution has set up a sharp
confluence/deformation zone across the southern Great Lakes. A
modest low level jet of around 20 knots is evident via KIND VAD
profile data this evening and moisture convergence at the nose
of this slightly stronger southerly flow appears to be setting
up a favored axis of shower development across central Indiana.
Through time, the accompanying west-east oriented sfc trough and
moisture convergence axis should lift into northeast Indiana
after 04Z with a potential of some heavier showers at KFWA
during the overnight hours. Precipitation prospects are more
limited at KSBN but some weak moisture convergence associated
with wind directional convergence could allow some more rain
showers in the 02Z-05Z timeframe.

Have maintained trend of IFR cigs at terminals tonight,
although the IFR conditions still appear to have a more limited
temporal window at KSBN in comparison to KFWA. Cigs should
improve to gradually on Saturday at KFWA, but relatively weak
mixing and abundant low level moisture will make this a slow
process. By mid morning Saturday, the threat of additional
showers should begin to slip southeast of KFWA as some veering
of low level flow takes better forcing south of the terminals.
An isolated thunderstorm is possible at KFWA tonight, but very
limited instability argues for a continued omission of mention
for now.

&&

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

&&

$$

UPDATE...Marsili
DISCUSSION...Brown
AVIATION...Marsili