742
FXUS61 KILN 201806
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
206 PM EDT Mon Jul 20 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...
Key Message 1) Thunderstorms are expected Tuesday, with a chance of
severe weather.

Key Message 2) Drier and cooler conditions expected through the rest
of the week.

&&

.DISCUSSION...
Key Message 1) Thunderstorms are expected Tuesday, with a chance of
severe weather.

As surface high pressure over New Jersey drifts off the Atlantic
coast this afternoon, a relatively dry and stable air mass over the
Ohio Valley will slowly begin to modify, with increasing southerly
flow bringing moisture into the area from the south. There is also
still some wildfire smoke in the area, though it is expected that
this will move northward and diminish this evening. Relatively quiet
conditions are expected through the majority of the overnight hours.

A deep upper trough and closed surface low are forecast to move east
through northern Ontario on Tuesday morning, as the axis of the
trough (and an associated surface cold front) are forecast to move
out of the upper Midwest and into the Ohio Valley at some point on
Tuesday. Forcing associated with this feature will bring
thunderstorms to the ILN forecast area on Tuesday, with some severe
weather possible. Confidence is very high that thunderstorms will
occur, but confidence in the overall severe magnitude and timing are
somewhat low, as early-day storms will have an impact on the
mesoscale environment and additional development.

Later today (Monday) it is expected that one or several clusters of
severe thunderstorms will develop over the upper Midwest. These
storms are expected to move southeast toward Indiana and Ohio during
the early morning hours on Tuesday. The storms will probably be in a
weakening state with the loss of diurnal heating, but there will be
enough theta-e advection aloft to keep up to 1000 J/kg of MUCAPE
around (even if much of this is elevated). Overall bulk shear will
actually be increasing at this time, so despite the limited
instability, these storms may bring a marginal risk for severe
weather (primarily wind). The timing for this first round of storms,
assuming the storms hold together, will generally be 6AM to 12PM.

Additional storms are likely to develop heading into Tuesday
afternoon -- perhaps an intensification of any leftover activity
from the morning, or perhaps new development in areas of significant
destabilization or remnant outflow boundaries. It would be very hard
to say exactly when and where this may occur, as it is all dependent
on mesoscale details from the leftover morning storms. Instability
will likely recover to some degree, with SBCAPE values of 1000-2000
J/kg on Tuesday afternoon, though the higher values are dependent on
areas where clearing occurs. Dewpoints getting into the lower to
possibly middle 70s will also contribute to the destabilization,
regardless of clearing and insolation. Shear will be notably high for
July, with 500mb WNW flow of 50-60 knots, 0-6km bulk shear of about
60 knots, and 40-45 knots of 0-3km shear. This shear is easily
sufficient for organized storms, potentially with some supercellular
structures early in storm development, but with a likely trend
toward clusters and bowing segments. This suggests a primary threat
of damaging wind. Some severe hail is possible, particularly with any
supercells that develop, though mid level lapse rates and an overall
warm environment would limit this somewhat. A tornado or two is also
possible, but this does not appear to be the main risk, as marginal
0-1km shear and rather veered surface flow may keep this risk more
limited. Finally, precipitable water values of around 2 inches
support very heavy rainfall. Though most of the activity will be
progressive (given the generally strong wind flow) some training
storms may occur, so there is a threat for some localized flash
flooding as well.

In summary, severe weather is certainly possible tomorrow, but the
afternoon threat remains somewhat conditional on destabilization and
early-day convective activity. It should be noted that if a scenario
were to occur where the morning storms quickly dissipate, greater
destabilization may occur on Tuesday afternoon in advance of
additional development, resulting in a greater severe weather risk.
As of now, while this scenario is possible, it does not appear to be
the most likely solution.

With so much uncertainty in how storm evolution will play out, the
overall timing forecast is probably best described diurnally for now,
roughly 2PM to 9PM. As the cold front moves south into the area, and
the atmosphere gets worked over, chances for severe storms should
diminish significantly during the mid to late evening.

Key Message 2) Drier and cooler conditions expected through the rest
of the week.

Surface high pressure will be moving into the area from the north on
Wednesday, behind the cold front mentioned in the section above.
This dry and relatively cool air mass will bring max temps down into
the 70s on Wednesday. Temps are expected to gradually warm by a few
degrees each day from there, with values near normal again (mid to
upper 80s) over the weekend.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Generally VFR conditions are expected through the rest of the day,
although some smoke could reduce visibilities through this afternoon,
and occasional MVFR conditions are possible.

Late overnight into early Tuesday morning, showers and thunderstorms
are expected to move into the area from the north. This has been
indicated in the TAFs with a prevailing -SHRA and PROB30 -TSRA
mention, though timing and confidence will keep the -TSRA mention out
of the Cincinnati TAF sites for now. Some MVFR ceilings are
possible Tuesday morning, even outside of any thunderstorms.

Additional thunderstorm development will be possible Tuesday
afternoon, though confidence in specifics is very low, as it will be
dependent on how things go with the thunderstorms in the morning.

OUTLOOK...Thunderstorms likely Tuesday afternoon into Tuesday
evening.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Air Quality Alert until midnight EDT tonight for OHZ042-043-051-053-
     060>062.
     Air Quality Alert until 9 PM EDT this evening for OHZ046-055-056-
     065.
KY...None.
IN...Air Quality Alert until midnight EDT tonight for INZ050-058-059-066.

&&

$$

DISCUSSION...Hatzos
AVIATION...Hatzos