Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 231923
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
323 PM EDT Sat Sep 23 2017

.SYNOPSIS...
A mid-level ridge of high pressure will remain over the region
through early next week. This will bring generally dry and warm
weather conditions to the region. Much cooler air will settle
into the region by the end of next week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Center of H5 ridge will shift from nrn Indiana to wrn NY state
overnight. This will keep skies will mostly clear tonight, but will
allow patches of cirrus to continue to drift in from the east.
Lingering low level moisture will allow for some development of
river valley fog again tonight.

Looking at lows generally in the lower 60s again, with some
locations in the east being able to drop into the upper 50s.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...
The H5 ridge will continue its transition off to the east on Sunday.
A se flow around the ridge could bring a few more cirrus clouds to
the region on Sunday. This combining with H8 temperatures a degree
or so cooler than today may steal a degree or two from the high
temperature, So went with highs in the upper 80s. The ridge remain
dominant Sunday night, keeping skies mostly clear. Lows drop to
between 60 to 65 degrees.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
The extended forecast period will be punctuated by a mid-week
pattern change over the Ohio Valley -- with warm and humid
conditions to start, and cooler conditions to end.

On Monday morning, there will still have been very little change to
the overall weather pattern that has existed for an extended period
of time. Mid level ridging will still be in place over the region,
as will surface high pressure -- though both will be centered east
of the Ohio Valley. With light boundary layer winds and a stagnant
air mass, a basically-unchanging forecast is warranted for both
Monday and Tuesday, with highs in the upper 80s and mostly clear
skies. It is possible that, as this pattern has shown in the past
day or two, max temps may need to be raised to closer to 90.

Late on Tuesday, a trough will be moving eastward from North Dakota
into the northern Great Lakes. Ahead of the trough, a weak surface
low will be moving northeast near James Bay by Wednesday morning,
with a weak and stretched-out cold front extending southward through
the Great Lakes region. Though attention will be placed on the role
this setup will have in shunting Hurricane Maria out into the open
ocean, the cold front will also have some impact on the Ohio Valley,
at least in terms of the cold advection that will follow its
passage. In terms of precipitation chances with the front on
Wednesday afternoon, it will be moving into a dry air mass, well
separated from its parent surface low, and lacking in forcing and
convergence. PoPs will be kept to only a 20 percent chance.
Depending on the exact position of the front, max temps on Wednesday
could vary a bit from NW to SE, so the temperature forecast for this
day is only of medium confidence at best.

A much larger and more well-defined trough will move southeast into
the Ohio Valley on Friday into Saturday, bringing a notable cooling
in temperatures, as well as at least some chance of precipitation.
Will keep PoPs on the far low end of the scale for now, as this
pattern evolution is a little bit uncertain, owing to the complex
interaction with the first trough and the hurricane.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
With high pressure at the surface and aloft the weather across
the region will be relatively benign. A few patches of cirrus
will work west across the tafs today. Then tonight, with the
weak easterly flow across the tafs, river valley fog should
form again. This is despite some increase H3 moisture from the
se, which might bring more patchy cirrus. Went with IFR fog at
KLUK from 07-12Z. The other tafs were left as VFR.

The fog should burn off by 13Z, leaving VFR conditions and a
just a few cirrus.

OUTLOOK...No significant weather expected.

&&

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

&&

$$
SYNOPSIS...Haines/Sites
NEAR TERM...Sites
SHORT TERM...Sites
LONG TERM...Hatzos
AVIATION...Sites



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