Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 210820

Area Forecast Discussion
National Weather Service Wilmington OH
320 AM EST Tue Nov 21 2017

As high pressure moves off the east coast, a cold front will move
into the Ohio Valley today, bringing some scattered showers to the
area. Cold air will move in behind the front as high pressure builds
into the region for Wednesday and Thursday. Temperatures will warm
slightly for Friday, before another cold front approaches the region
early in the weekend.


Surface high pressure is moving off the east coast, as an area
of surface low pressure north of Lake Superior gradually moves
ENE into northern Quebec. A cold front extends southwest from
this low, and is forecast to cross the Great Lakes and Ohio
Valley through this afternoon and evening. This front remains,
at least as forecast, not the strongest weather feature ever to
move through the region. Nonetheless, confidence is increasing
in the chances for precipitation -- particularly across the
northern half of the forecast area. This is not so much tied to
the surface front as to upper jet support and forcing from the
mid-level shortwave, as the precipitation is actually expected
to occur behind the surface wind shift. Various WRF runs suggest
it will be a relatively narrow band of light rain, weaker with
southward extend, to the point that there was not quite enough
confidence to include PoPs all the way to the southern ILN
border. As temperatures cool behind the cold front, it will be
close as to whether or not this will occur quickly enough to
allow for any snow to mix in, but this forecast will lean on the
side of precipitation cutting off before this occurs.

Gusty winds will also be an issue today, with gusts in the 20-30
knot range expected, primarily in the northern half of the
forecast area. It is interesting that the strongest 925mb/850mb
winds are already moving through the region right now, which
means that there will be slightly less to mix up into during
diurnal timing later this morning and afternoon.

With frontal timing primarily expected to be an evening issue,
temperatures through the period should be roughly diurnal.


After the passage of the cold front late Tuesday, a relatively
simple weather scenario is expected for Wednesday, as surface
high pressure begins to nudge into the area from the middle
Mississippi Valley region. Deep-layer NW flow will keep a cold
advection pattern in place, resulting in conditions that will be
notably cooler (highs in the upper 30s to lower 40s) and
somewhat drier (dewpoints in the mid 20s) than on Tuesday. One
concern is in how quickly the post-frontal stratocumulus clouds
will clear out behind the front, and expectations are that these
clouds will likely not dissipate immediately -- persisting, at
least in part, through Wednesday morning.


Surface high pressure will settle across the Ohio Valley Wednesday
night. It will initially start out mostly clear, but a weakening
disturbance in the northwest flow aloft will spread some mid and
high level clouds into the region overnight. Temperatures should
bottom out in the lower to mid 20s.

Thanksgiving Day will be dry as high pressure continues to influence
the region. Under a mix of clouds and sunshine, it will be chilly
with highs in the lower to mid 40s.

For Thursday night into Friday, a mid level trough will dig
southeast from the western provinces of Canada into south central
Canada/northern Plains. As this occurs, a cold front will push
southeast.  WAA ahead of the front will boost temperatures into the
upper 40s and lower 50s on Friday.

For Friday night into Saturday, mid level trough will dig east into
the Great Lakes and the Ohio Valley. Aforementioned cold front will
move east through our region Friday night into Saturday morning.
Moisture is limited, and some models, such as the ECMWF, move the
front through dry. Thus, will keep PoPs in the slight chance/low
chance range north of the Ohio River. Skies are expected to be
partly cloudy behind the front on Saturday. Given a warm start,
sunshine, and relatively weak CAA, we should see highs similar to
Fridays readings (upper 40s to the lower 50s).

For Saturday night into Sunday, secondary energy will dig into the
western side of the mid level trough, strengthening it over eastern
Canada, the eastern Great Lakes, and New England. This will push a
secondary cold front through the region. It appears that CAA
stratocumulus will develop and remain over the area, with cloud
coverage greatest north and east downwind of the Great Lakes. At
this time, lake effect snow showers appear poised down wind of the
eastern Great Lakes, so we will keep a dry forecast going.  There is
an outside chance of a few flurries in our northeast zones if the
cloud layer ends up intersecting the favored dendritic growth zone.
It will be a cold day with highs ranging from 35 to 40.

Finally, for Sunday night into Monday, mid level trough will
progress east, allowing high pressure to build into the region.
After a cold start in the lower to mid 20s Monday morning, highs
will still only warm into the 35 to 40 degree range.


VFR conditions are generally expected through the TAF period.
LLWS will be the main concern through the overnight hours, with
strong southwesterly winds just off the surface. Surface
southwesterly winds will increase during the day, with gusts
into the 20-25 knot range (possibly slightly higher at Dayton
and Columbus).

A cold front will move through the area during the evening,
switching winds to the WNW. Winds may be slightly gusty again
(20 knots or so) immediately behind the front. There is a chance
of some passing showers, mainly at the northern TAF sites, and
this will be covered with a VCSH. There is also a slight chance
of some MVFR ceilings around this time frame, but prevailing VFR
conditions still appear most likely.

OUTLOOK...No significant weather expected.




NEAR TERM...Hatzos
LONG TERM...Hickman
AVIATION...Hatzos is the U.S. government's official web portal to all federal, state and local government web resources and services.