Area Forecast Discussion
Issued by NWS Wilmington, OH

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980
FXUS61 KILN 210834
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
434 AM EDT Tue Mar 21 2017

.SYNOPSIS...
Temperatures will be near seasonal normals today in the wake of
a cold front which will push south away from the region. High
pressure will build southward into the Great Lakes and Ohio
Valley tonight, settling across the area on Wednesday. Much
colder temperatures can be expected with this high. The high
will move east Wednesday night into Thursday. After a cold start
Thursday morning, temperatures will moderate through the end of
the week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Dense fog has become expansive enough to warrant a Dense Fog
Advisory for parts of the region, mainly along and north of
I-70, which includes the Dayton and Columbus metro areas. Have
issued the advisory until 9 am EDT. Winds will pick up toward
morning, but it is unclear how fast this will improve the
visibility before sunrise.

For later today, low level moisture becomes quite shallow
between 12Z and 15Z. Therefore, with daytime heating and
turbulent mixing, we should see low clouds and fog lift and
scattered out by afternoon. Unfortunately, there will be
considerable mid and high level clouds in a northwest flow
aloft, so peaks of sunshine will be limited.

Models have backed off on the threat for a few showers across
our southern CWFA late this afternoon into this evening in
association with an embedded s/wv. It now appears that mid
clouds will thicken with perhaps some virga occurring from the
mid deck. Highs today will range from the lower 50s north to
the lower 60s south.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
For tonight into Wednesday, a large scale mid level trough will
dig southeast into southeast Canada/New England. A surface cold
front associated with this trough will push south through the
region overnight. This front is expected to be dry, and will
mark the beginning of colder and drier air. Mid and high level
clouds will decrease gradually overnight as north winds
increase and become locally gusty in the 20 mph to 30 mph
range. Low-level CAA will drop overnight lows from the lower 20s
north to near 30 along and south of the Ohio River. On
Wednesday, high pressure will build south into the Great Lakes
and Ohio Valley. We should see a good deal of sunshine, with
some mid and high level clouds increasing from the west late in
the day. Despite the sunshine, a cold start and continued CAA
will keep temperatures chilly for late March. Highs will range
from the upper 30s north to the lower 40s south.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
A fairly strong area of surface high pressure will be in place
across the Great Lakes on Wednesday evening, providing a generally
dry and cold air mass, extending southward across the upper
half of the Ohio Valley. This will likely lead to Wednesday
night being the coldest night of the forecast period, though
there is some concern with some mid-level clouds potentially
moving in from the southwest, at least across the southwestern
half of the ILN CWA. However, as long as these clouds are not
especially thick, the CWA should drop completely into the 20s --
with the potential for upper teens in outlying / rural areas in
central Ohio.

An amplifying 500mb pattern will be occurring even as relatively
tranquil conditions are expected through Thursday, with heights
rising as ridging builds over the Mississippi Valley. This will
eventually lead to unsettled conditions through the Ohio Valley on
Friday and Saturday. With upper/mid ridging moving into the region
late Thursday into Friday, a warm advection pattern is expected to
begin. This required a non-diurnal temperature trace for Thursday
night into Friday morning, with min temps early in the overnight
hours, and slowly rising temperatures by morning. As this occurs,
some isentropically-driven precipitation is expected, mainly Friday
morning. The feed of moisture transport, however, is weak -- and not
strongly connected to the Gulf of Mexico. With marginal deep-layer
moisture and most of the warm frontal forcing focused further to the
north, there are no signs of heavy precipitation as of now, and PoPs
have been kept on the low end of the scale. After this activity
shifts north and east of the region, dry conditions are expected
going into Saturday, with the ILN CWA expected to be in the warm
sector of the developing system to the west.

By Saturday afternoon and evening, attention will turn to a
developing stacked low pressure center moving through Missouri.
Confidence has increased in the overall timing and placement with
this system, and it is now expected that there will be several
rounds of showers (and potentially thunderstorms) along with this
system -- running from Saturday evening through Sunday afternoon. As
such, PoPs have been increased to the 50-70 percent range, with
thunder kept in the forecast for Saturday afternoon, and a slight
chance of thunder added for part of the area on Sunday afternoon.
This system will have a respectable feed of theta-e and a
tight/compact 850mb-700mb low, so forcing and moisture should be
sufficient for widespread precipitation. The possibility for heavier
rainfall or strong storms is less certain, owing to differences in
model specifics and a pattern that is not necessarily a classic
setup for either threat. Nonetheless, there is at least a low-end
potential to watch and refine the forecast for in the next few days.

A narrow ridge behind the stacked low will provide a reasonable
chance for dry conditions for Monday, before unsettled conditions
become more likely going into the rest of the week.

The warming trend on Friday and Saturday is likely to bring
temperatures into the 60s, possibly near 70 in the southern half of
the CWA on Saturday, depending on when precipitation moves in. Near
and behind the low on Sunday and Monday, temperatures will cool
slightly, but should still remain above normal.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
Plenty of low level moisture remains across the region early
this morning in the wake of exiting cold front. Aviators can
expect IFR/LIFR/VLIFR conditions with the lowest conditions
expected over by KDAY. There should be an improvement to the
visibility between 10Z and 12Z as winds begin to increase from
the north which will allow for some mixing. Otherwise, the low
level moisture becomes fairly shallow after 12Z. Thus, with day
time heating and turbulent mixing, IFR ceilings should lift and
improve to VFR by 18Z as the low level moisture scatters out.

For late this afternoon and this evening, a weak cold front
will begin to push into the region from the north. Also, an
embedded disturbance will move across the area. Mid clouds will
thicken with the disturbance. Measurable precipitation is not
forecast, although some virga may occur.

For the overnight period, weak cold front will push south
through the region. Its passage will be marked with a little bit
of stronger winds with wind gusts in the 20 to 25 knot range.
Much drier and cold air will filter into the Great Lakes and
Ohio Valley with mid and high clouds shifting off to the
southeast toward 12Z Wednesday.

OUTLOOK...MVFR ceilings and visibilities likely Saturday along
with a chance of thunderstorms.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...Dense Fog Advisory until 9 AM EDT this morning for OHZ026-034-
     035-042>046-051>056-060>062.
KY...None.
IN...Dense Fog Advisory until 9 AM EDT this morning for INZ050.

&&

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



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