974
FXUS63 KIWX 160041
AFDIWX

Area Forecast Discussion
National Weather Service Northern Indiana
841 PM EDT Sat Aug 15 2026

.KEY MESSAGES...

- An isolated strong to severe storm or two possible between 6
  and 9 PM EDT today, mainly east of I-69 and the US 30
  corridor. Main threats will be damaging winds and an isolated
  tornado.

- Additional round of rain and sub-severe storms likely between 4 AM
  and Noon EDT.

- Flood Watch continues along and south of US 30 where heavy rain
  will continue to exacerbate ongoing flooding through Sunday.

- Dry conditions return Monday and Tuesday.

&&

.UPDATE...
Issued at 828 PM EDT Sat Aug 15 2026

An MCV continues to slowly track across far northeast Indiana
and northwest Ohio this evening. As this feature has tracked
eastward, a weak to modest surface based instability axis on
the order of 1000 J/kg has migrated as far north as the US Route
24 corridor. Downstream of this MCV, convective activity has
increased with a instances of some weak low level rotation. As
mentioned in previous discussions, presence of this MCV
feature, low LCLs, and proximity of a 100 m2/s2 0-1km SRH pocket
will be conducive for a very low probability of funnel clouds
and perhaps a brief weak tornado through 02Z. To the north,
across far northern Indiana and southern Lower Michigan, a few
funnel cloud reports have also been received along what appears
to be weak west-east boundary likely enhanced by the eastward
progression of the MCV. Non-supercell tornado parameters do have
a relative maximum along this boundary and cannot discount a
few more instances of funnel clouds through sunset. Convective
parameters are much more unfavorable for any significant severe
weather across these locations. Additional thunderstorms are
expected overnight into early Sunday morning as broad warm/moist
advection produces increasing elevated instability. There is a
potential that the bulk of this activity may remain north of
areas most sensitive to additional heavy rainfall/flooding
concerns. A Flood Watch will remain in place however through 15Z
Sunday for areas roughly south of US Route 30.

&&

.DISCUSSION...
Issued at 1230 PM EDT Sat Aug 15 2026

Stratiform rain continues to diminish as of midday, although there
are still some areas of light rain ongoing south of US 24. Visible
satellite shows a few pockets of clearing as an MCV approaches the
IL/IN border, but more widespread breaks in the clouds will be
needed to recharge the atmosphere for potential storms this
afternoon and evening. It is worth noting that isolated strong to
severe storms are still possible despite the downgrade from SPC to a
Marginal Risk (level 1 of 5) for severe weather today. The
aforementioned MCV is expected to move across northern Indiana this
afternoon and evening. Storm development is possible between 4-8 PM
EDT today. Coverage will likely be spatially limited as the better
environment is off to our southwest, however, I think the best
chances for isolated severe weather today will be mainly east of I-
69 and along/south of US 30. This would include Grant, Blackford,
Jay, Wabash, Adams, and Allen counties in Indiana and Defiance,
Henry, Putnam, Paulding, Putnam, and Van Wert in Ohio. Models vary
widely on a solution, with some showing no storms and some showing
discrete cells capable of producing severe weather. 30-40 kts of 0-
6km shear, 100-200 m2/s2 of 0-1 SRH, and a narrow corridor of
moderate instability may develop along the I-69 corridor
depending on how much clearing we can get this afternoon. This
would be a favorable environment for damaging winds and an
isolated, brief tornado. With a low end severe threat, this is a
highly conditional setup depending on clearing and how much the
atmosphere has been depleted by this morning`s rain. Despite
favorable shear and instability, poor lapse low and mid level
rates can be seen in forecast soundings from most of the CAMs,
which will likely be a limiting factor.

WPC does have a Moderate Risk (level 3 of 4) for excessive rainfall
along and south of US 30 today, where a Flood Watch is in effect.
Strong moisture transport is expected and precipitable water values
will once again be at or above 2 inches today. With such high
moisture content in the airmass overhead (99th percentile PWATs and
dewpoints well into the 70s), any storm could be a very efficient
rainfall producer with rain rates between 1-2" per hour. Given that
the ground is so saturated south of US 30, where 6-12"+ of rain has
fallen since this past Tuesday, renewed flash flooding in areas that
have already been hard hit is becoming an increasing concern. On
the very very low chance that an isolated tornado occurs in
east-central Indiana somewhere in Wells, Adams, Grant,
Blackford, and Jay counties where areal and river flooding is
ongoing, the best recommendation is to safely shelter in the
lowest level away from windows and doors but to stay away from
flooding.

One last round of scattered rain and storms is likely Sunday
morning, becoming more isolated into the afternoon hours. We will
have to monitor convection in eastern Iowa and northern Illinois
overnight that will move eastward. Unfortunately, the axis of
heaviest rain looks to be south of the US 30 corridor before
daybreak Sunday as the LLJ ramps up with the stationary front in the
vicinity. High PWATs and dewpoints will contribute to efficient,
heavy rainfall late overnight into Sunday morning. The primary
timeframe for rain and storms looks to be between 4 AM to Noon
EDT. An isolated strong storm is possible south of US 24, but
once again, flooding is expected to pose a higher threat
spatially than severe weather. Due to this potential, the
current Flood Watch has been extended to last until 8 AM EDT
Sunday.

A welcome break from daily rain and storm chances is ahead!  We
finally see a reprieve in the `Ring of Fire` pattern Monday and
Tuesday as high pressure builds across the Great Lakes. This will
allow for the area to dry out, floodwater to recede, and for
river levels to fall. Temperatures will be seasonable with highs
in the upper 70s to near 80 degrees with lots of sun.

Another chance for rain and storms comes Wednesday with a cold
front, although it may be short lived as high pressure looks to
return over the Great Lakes once again. After a very active first
half of August and a Top 10 wettest August on record for some
locations already, we would happily welcome a stretch of dry weather
by the end of the week into next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 756 PM EDT Sat Aug 15 2026

An MCV tracking across far northeast Indiana and northwest Ohio
is combining with a weak instability axis for some convective
development this afternoon. This focus is expected to remain
east of KFWA this evening. Additional showers and isolated
storms are expected to develop overnight in a broad low level
theta advective regime. Some mid level support via a weak mid
level trough is expected to approach from the Corn Belt, but
overall organization is expected to be limited with these
showers and storms. Did include PROB30 to cover this potential,
although confidence in timing is on the lower side. A lull in
showers is expected later Sunday morning, but lower coverage
convection is possible with the actual cold frontal boundary
toward end of this period. Confidence remains too low for
inclusion at this time. Otherwise, cigs should deteriorate to
MVFR again tonight, and possibly IFR for a time before improving
through the morning on Sunday.

&&

.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through Sunday morning for INZ012-013-015-020-
     022>027-032>034.
OH...Flood Watch through Sunday morning for OHZ024-025.
MI...None.
MARINE...None.

&&

$$

UPDATE...Marsili
DISCUSSION...Johnson
AVIATION...Marsili