Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 181905

Area Forecast Discussion
National Weather Service Wilmington OH
305 PM EDT Wed Oct 18 2017

Strong high pressure over the Mid-Atlantic will continue to
provide pleasant fall weather over the area. A weak cold front
will wash out before reaching the area on Thursday, but a few
clouds may drift across the area Thursday afternoon and night in
association with this feature. Dry weather will continue for
much of the weekend, before the next cold front and low pressure
system will increase the chances for rain by late in the weekend
into early next week.


Generally clear skies and light winds tonight, although a few
bands of cirrus tied to weak shortwave energy moving through the
flow will cross Kentucky and southern Ohio this evening. Added
some valley fog to the forecast for later tonight, though
development will be more conditional/uncertain tonight vs.
previous nights, thanks in part to increasing gradient in/above
the boundary layer as high pressure drifts off to the east, and
weak/dying front approaches from the northwest. Think the best
chance of valley fog will be in the Scioto Valley - furthest
removed from gradient flow, but have also expanded valley fog
along the Ohio River and associated tributaries as winds are
expected to drop below 4 kts in these areas. The more sheltered
the valley - the better the chance at some fog. Temps tonight
should run a little warmer than last night - though areas of
central Ohio may approach the upper 30s esp Hocking County on to
the south toward Lewis County, KY.


Quiet, but warmer weather is expected on Thursday. Weak front
tied to shortwave energy crossing southern Canada will lose
identity with southern extent, and by later in the afternoon
should be stretching from northern Indiana/northern Ohio through
Lake Erie and Ontario. Modest southwesterly breezes and very
little moisture advection should make for efficient warming of
the boundary layer - especially in the afternoon as winds turn
west-southwesterly - a favorable direction for temps to run
above guidance when boundary layer is dry. So running temps a
few degrees above blends/guidance for Thursday afternoon
underneath what should be ample sunshine. Forecast soundings
just not showing any appreciable moisture for cloud cover
outside of a little cirrus.

Thursday night is another quiet/calm night as surface high
pressure redevelops/reasserts itself over WV/KY/TN. Clear skies
and seasonable temperatures in this regime.


Upper ridge combined with increasing southerly flow will result in
much above normal temperatures along with a continuation of dry
conditions through at least the first half of the weekend.

Upper ridge will move east as troughing approaches from the west.
Northern stream will break off and track through the Great Lakes
late Sunday into early Monday. This will cause a cold front to
slowly push into the area with increasing chances of showers. The
southern stream will briefly close off, which will slow the front`s
progression. There will be a secondary surge of moisture traveling
along the slow-moving boundary late Monday into Monday night.

A more energetic  northern stream system will begin to carve out a
long wave trough which will migrate from the upper Mississippi
Valley on Tuesday into the Ohio Valley/Great Lakes region on
Wednesday. This will result in much cooler conditions. Wednesday
will likely being the coolest day of the week with temperatures
nearly 10 degrees below normal. In addition, there will be primarily
diurnal showers both Tuesday and Wednesday.


VFR conditions expected through the period, although some valley
fog is likely to plague KLUK as it has in recent mornings. Clear
skies this afternoon into tonight as flow begins to drop off
with boundary layer cooling. Don`t expect winds to go calm
however as increasing gradient will offset radiational component
to a degree, so expect light SSWLY flow to maintain in the 3-6kt
range at most sites through the night. Given how dry the
boundary layer is, this should keep most fog at bay. However
sheltered valleys may drop off enough to form a shallow fog
layer after 07Z, so included this at KLUK.

Expect winds to be a little stronger out of the southwest on
Thursday but expect very few clouds aside from a little cirrus.

OUTLOOK...No significant weather expected.




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