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fxus61 Kiln 200828 

Area forecast discussion
National Weather Service Wilmington Ohio
328 am EST Mon Nov 20 2017

high pressure across the Ohio Valley this morning will move to
the Carolinas this evening. A cold front will move east into the
western Great Lakes tonight, and then across the remainder of
the Great Lakes and Ohio Valley Tuesday into Tuesday night. High
pressure will return to the region for Wednesday and Thanksgiving
day. Temperatures near normal will drop to below normal
readings for Wednesday and Thanksgiving day.


Near term /until 6 PM this evening/...
the region will be under the influence of a quasi-zonal upper
level flow today. At the surface, high pressure extending into
the Ohio Valley this morning will move toward the Carolinas by
this evening. An embedded disturbance will bring some cirrus to
the area, providing filtered sunshine. The pressure gradient
will be tightest across our northwest, resulting in local
southerly wind gusts in the 20 to 25 knot range. Temperatures
will warm into the mid and upper 40s, which is near or slightly
below normal.


Short term /6 PM this evening through Tuesday night/...
as the center of the high moves off the Carolina coast tonight,
a cold front will move east into the western Great Lakes. We
should see some cirrus overnight, some from the departing
disturbance and more ahead of the next system. Winds will stay
up with some local gusts developing overnight across the
northwest as the gradient tightens well ahead of the cold front.
Lows will range from the lower to mid 30s.

On Tuesday, mid level S/WV will dig southeast into the Great
Lakes. As this occurs, the cold front will move southeast,
entering our northwest zones by late in the day. Models have
trended wetter with this front, such that a chance of showers is
now in the forecast for the northwest late Tuesday afternoon.
Clouds will increase from northwest to southeast throughout the
day. It will be breezy with wind gusts in the 20 to 30 knot
range. Highs will range from the upper 40s northwest to the mid
50s southeast.

For Tuesday night, mid level S/WV is expected to pivot east
across the southern Great Lakes, pushing the cold front through
our area. Again, the models have trended wetter, so now have a
chance of showers for the northern/eastern zones where forcing
and moisture will be the greatest, tapering off to a slight
chance elsewhere. Precipitation will occur mostly in the
evening, departing by early morning. Partial clearing is
expected overnight with temperatures falling into the upper 20s
to the lower 30s by morning.


Long term /Wednesday through Sunday/...
the cold front will be east of the area by Wednesday morning, with
cold advection occurring across the area, as surface high pressure
begins to move into the region from the middle Mississippi Valley
region. As the depiction of this cold front has continued to
strengthen in the models, so has the cold air behind it, resulting
in a 10-15 degree drop in Max temps from Tuesday to Wednesday (a
little more pronounced than in previous forecasts).

A fast (if wavy) northern stream will set up across the northern
Continental U.S. / Southern tier of Canada through the rest of the extended
forecast period. The Ohio Valley will largely remain in a regime of
weaker westerly / northwesterly flow to the south of the stronger
jet, at least through the rest of the week, with some adjustment as
a shortwave builds southward on Saturday.

There has been some consolidation of model solutions with regards to
this wave, and a cold front that will also move through the region
at around the same time. With warm advection Friday night into
Saturday morning (and likely non-diurnal temperatures) conditions
should be warm enough to allow for rain as the precipitation type
when the front crosses the area. Nonetheless, with limited moisture
(as will be the case through the entire extended forecast period)
pops will be kept on the low end.


Aviation /08z Monday through Friday/...
a mid level trough will move away from the region today,
bringing back a quasi-zonal flow pattern aloft. At the surface,
a ridge of high pressure will nose into the region this morning,
then its ridge axis will shift southeast through the day. Some
high clouds will move into the area as a weak disturbance
rotates east. Winds will become south, with local gusts up to
20 knots near the northern terminals between 16z and 22z.

For tonight, weak disturbance moves east, but more high level
clouds will approach from the northwest as a mid level
disturbance drops southeast into the upper Mississippi River
valley/western Great Lakes. Low pressure and a cold front with
this feature will begin tightening the surface pressure gradient
overnight. Above the surface, a fairly decent low level jet will
move southeast into the region. This will bring the threat for
non-convective low level wind shear conditions, developing between 03z and 06z. significant weather expected.


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