Area Forecast Discussion
Issued by NWS Wilmington, OH

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000
FXUS61 KILN 191055
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
655 AM EDT Tue Jun 19 2018

.SYNOPSIS...
A cold front will move south into the region today, bringing
the threat of showers and thunderstorms. The front will remain
in the area tonight and Wednesday, continuing the threat of
showers and thunderstorms. The front will gradually stall out
near the Ohio River by Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Models agree that a cold front will move south into our region
today. The main change from the previous forecast is that the
eastern end of the front is expected to move farther south than
the western end of the front. This will result in a northwest to
southeast frontal axis through our forecast area by this
afternoon. Plenty of moisture will accompany the front as PWATs
approach 2 inches. The combination of diurnal instability
(1500-2000 J/kg of MLCAPE) and low level frontal convergence
will allow showers and thunderstorms to increase in coverage
during the afternoon hours. Again, the best chance will bisect
the forecast area, occurring near and on the most unstable side
of the boundary. A few strong to severe storms can not be ruled
out this afternoon and evening given favorable DCAPE/delta theta
e values (wet microburst). However, organization will be limited
given that the best deep layer shear will remain north of the
greatest instability axis. Large hail will be limited given
overall poor mid level lapse rates and wet bulb zero values near
13 kft. Localized flooding will be a concern given the high
PWATs. Will mention damaging winds and localized flooding in the
HWO for today. Temperatures will range from the lower 80s far
northeast to near 90 along and south of the Ohio River. Given
max temperatures near 90 and dewpoints in the lower 70s,
locations along and south of the Ohio River will see heat index
values in the upper 90s. These values should be brief in
duration as showers and thunderstorms bring relief. An SPS has
been issued to account for this.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Convection will show a diurnal down tread this evening given
decreasing instability and lack of strong overall forcing.
Models suggest that an area of low pressure may move into the
area from the west overnight in association with an upper level
disturbance. The main effect from this feature will be possibly
pushing the front slightly back to the north. Otherwise,
considerable cloudiness is expected given debris clouds from
convection. Lows will range from the upper 60s north to the
lower 70s south.

On Wednesday, models indicate that a weak disturbance may
accompany the weak low as it traverses east along the frontal
boundary. As this occurs, the boundary will begin to make a move
toward the south by mid to late afternoon. Wednesday will be
similar to Tuesday in terms of hazards. Best deep layer shear
will remain to our north, but moderate instability (1500-2000
J/kg) will develop once again during the heat of the day. This
will result in showers and thunderstorms with limited
organization, but a few strong to severe storms with wet
microburst potential can not be ruled out. Large hail will be
limited again due to poor mid level lapse rates. Localized
flooding will remain a concern given PWATs near 2 inches. Will
make a mention in the HWO about these hazards. Highs will range
from the lower to mid 80s.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
The extended forecast period looks fairly active, with chances for
convection through much of the next week.

On Wednesday night, a WNW-to-ESE oriented surface front will be
slowly moving south through the ILN CWA, and ongoing convection
will likely be impacting the southern half of the forecast
area. A diminishing trend is expected overnight, before the
boundary likely activates yet again on Thursday. Given the slow
motion of the boundary, and the very weak flow atop it, some
heavy rain potential will likely exist yet again. In fact,
precipitable water values are expected to get close to two
inches. So, flash flooding may be possible, even if the severe
threat appears on the low end of the scale given the lack of
shear and generally moist profile.

The pattern will begin to change a bit on Friday, as stacked low
pressure begins a slow eastward trek out of the middle Mississippi
Valley region. This will amplify the pattern a little bit over the
Ohio Valley, forcing a northward shift in the warm sector, and
placing most of the ILN CWA into a regime favorable for ascent.
While wind fields should remain weak, there will be some directional
shear in a moist air mass, presenting some concern for severe
weather. However, it would be preferred to wait to see where and how
the forcing will set up before adding anything to the HWO for what
looks to be a marginal threat at this point -- especially with
marginal instability due to poor lapse rates.

Timing uncertainties for convective potential become more pronounced
over the weekend, with some issues regarding the timing of the low
as it ejects northeast into the Great Lakes. PoPs will be kept in
the chance category for Saturday and Sunday, but it should be noted
that there is some potential for greater thunderstorm coverage than
is currently indicated -- and a slight increase in shear as well.
Going out into Day 5 and Day 6 of the forecast, having some
uncertainty is not unusual. However, by Monday morning, there is
fairly good model agreement in high pressure building into the Great
Lakes from the north -- at the very least indicating a lower
probability of precipitation heading into the start of the week.

Not seeing much change in temperatures through the period, with
generally lower to mid 80s for highs, and no appreciable change in
air mass expected through the beginning of next week.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
A cold front is now forecast to sag a little farther south into
the region today where it will eventually stall. The northwest
to southeast orientation across our area will become the focus
for showers and thunderstorms.

Diurnal heating will combine with low level frontal forcing to
produce showers and thunderstorms, most numerous between 18Z and
00Z. All terminals run the risk of seeing a thunderstorm, but
moreso for the western/southern sites of KDAY/KILN/KCVG/KLUK. As
a result, have placed a predominate MVFR -SHRA and VCTS when
the peak threat is expected. Given the very moist airmass in
place, thunderstorms will be capable of producing locally very
heavy rain which will result in MVFR ceilings and at least IFR
visibilities. Will hone in on this threat with later TAF
issuances as confidence increases.

For this evening, showers and thunderstorms should diminish in
coverage.

For the overnight period, models indicate that a weak area of
low pressure in association with an upper level disturbance will
move into the region along the front. This may temporarily push
the front back a little north overnight. Chances of showers and
thunderstorms will be about 20 to 30 percent near the terminals
by then, with considerable debris clouds left over in the VFR
category.

OUTLOOK...Showers and thunderstorms are possible at times
through Saturday.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.

&&

$$
SYNOPSIS...Hickman
NEAR TERM...Hickman
SHORT TERM...Hickman
LONG TERM...Hatzos
AVIATION...Hickman



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