Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 012308

National Weather Service Wilmington OH
708 PM EDT Mon Jun 1 2020

As high pressure retreats to the east tonight, a warm front will
develop in the Great Lakes. Above normal temperatures and higher
humidity levels return Tuesday and will last through the week. An
area of thunderstorms will drop through the Great Lakes, affecting
the region Wednesday afternoon and Wednesday night. Rain chances
will linger over the region for the later part of the week.


Weakening echoes area dropping southeast across the Tri-State.
Most likely this will be nothing more than sprinkles early this
evening. Low levels are very dry and remain that way through the
night. The tail end of precipitation moving across the Great
Lakes may brush by central Ohio later tonight. Cannot rule out
some location getting .01 in but again more likely to be some
sprinkles. Forecast lows look reasonable at this point.


Region will be warm sectored for Tuesday as a warm front
develops over the Great Lakes. Plenty of sunshine is expected.
Highs will jump into the mid 80s and humidity levels will begin
to increase.

By Tuesday night the region will remain on the northern edge of
high pressure, which is centered of the southeast coast. This
will keep the area dry. Lows will be well above normal, only
dropping back into the mid to upper 60s.


Active start to the long term period as a frontal boundary
approaches the forecast area from the north. Temperatures start warm
as southwesterly flow around the northwest periphery of a ridge
continues to advect warm/moist air northeastward into the Ohio
Valley. Current expectations are that most of the area starts cloud
free with perhaps some mid-upper level clouds extending southward
from weakening nighttime convection to the north. This allows for
plentiful heating into the afternoon with mid to upper 80s area
wide. Low 90s are possible in warmer locations with NBM
probabilities still around 40%. Late in the afternoon, thunderstorms
are expected to initiate along the frontal boundary stretched across
north-central Ohio as shortwave energy moves through the northwest
flow. There is some uncertainty as to how decaying convection from
overnight Tuesday may play a role on convective initiation on
Wednesday, but mesoscale boundaries are difficult to predict several
days in advance. For now, expect thunderstorms to develop north of I-
70, late in the afternoon on Wednesday.

Regarding Severe Potential Wed-Wed Night- Day 3 SLGT risk from SPC
currently issued for much of the area with marginal risk across the
south. Highest confidence for severe storms during the late
afternoon is positioned north of I-70 where capping inversion is
eventually overcome between 5-6 PM. Explosive initiation along the
west to east boundary is indicated in Simulated IR from both the NAM
and ECMWF. With an unstable environment and effective shear between
25-30 knots, multi-cell clusters capable of damaging winds and hail
are expected during the late afternoon and evening hours as
instability is maximized. Heading into the evening, multi-cell
clusters may upscale into a couple southward progressing linear
segments for a couple hours. Toward the late evening, questions
remain as to how prolonged the severe threat lasts, as instability
decreases and storm elements move south of the strongest shear.
Additionally, westerly shear will favor north to south oriented
linear segments vs east to west as cold pool advancement to the
south likely results in outflow dominated storms. This would lead to
gradual weakening as storms move southward.

Regarding Flood Threat Wednesday Night: WPC day 3 outlook places
most of the area in a marginal threat for flash flooding. Despite
trends toward weakening storms into the overnight, instability
persists within modest westerly flow resulting in some potential for
backward propagating convection through the overnight. As the
overnight progresses, thunderstorms become more efficient rain
produces as the atmospheric column moistens with additional moisture
advection from the west. Mesoscale processes become the primary
focus overnight as they play a role in focusing heavy rain over
localized areas. These details are still uncertain 3 days in
advance, but the potential for localized flash flooding is becoming
more apparent.

For Thursday, ongoing showers and thunderstorms are still expected
during the morning hours as the frontal boundary begins to weaken.
New synoptic energy in the form of a shortwave trough moves into the
Ohio Valley resulting in another round of showers and thunderstorms.
Activity from Wednesday may limit some heating on Thursday, but
sufficient diurnal heating and a rather moist atmosphere in place
should still result in a new period of convective initiation, this
time focusing along and south of I-70. While the severe threat is
lower for this period of convection, continued heavy rain over
increasingly saturated ground may lead to additional flood concerns.

A third and final period of convection occurs on Friday as another
shortwave moves over an area of increasing instability across the
Ohio Valley. Although some severe storms are certainly possible,
Friday would be the third day in a row of widespread convection for
the forecast area. So, while still 5 days away, heavy rain leading
to local flash flooding and perhaps now river flooding, is the
primary concern. Temperatures remain above normal.

For Saturday through Monday, guidance is coming better in line with
a deepening trough over the Northeast and an amplified ridge in the
central US. This will help to dry out the Ohio Valley and keep
temperatures near to slightly above average.


VFR will prevail through the TAF period with just mid and high
clouds moving across the region. South winds will become
southwest after 12Z and increase during the day. There could be
some gusts up to 25 kt.

OUTLOOK...Thunderstorms are possible Wednesday afternoon into
Friday night.




LONG TERM...McGinnis
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