Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 250554
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
154 AM EDT Sun Sep 25 2016

.SYNOPSIS...
A weak cold front has stalled across the area this afternoon and
will wash out this evening. High pressure will then build into the
area Sunday. A stronger cold front will push across the Great Lakes
and Ohio Valley on Monday. Above normal temperatures will cool
toward more typical late September readings early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Weak surface cold front has stalled out across Kentucky with
surface high pressure building into the Great Lakes. Low level
moisture lags the front but drier air eventually advects in from
the north. Expect mainly clear skies overnight and light northeast
winds. Lows to range from the lower 50s north, where drier air
will exist to the lower/middle 60s south.


Previous Discussion...
A weak cold front has stalled across the area this afternoon and
will wash out later this evening. There is some left over cloud
cover along the front at KDAY and KILN which will continue to
erode through the day. Overnight into Sunday morning surface high
pressure will be centered over New England and edge into the area.
This will make for a temperature gradient across the area with the
coldest temperatures towards the northeast.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY NIGHT/...
Sunday afternoon the washed out cold front will start heading
north as a warm front as a much stronger front approaches from the
west. During the day Sunday the ILN forecast area will be in
between two upper level lows with mid level ridging amplifying over
the area. The broad upper level low over the western United States
will start to pull northeast and merge with a shortwave trough
over southern Manitoba. Another piece of energy will break off
from the low and head southwest towards the Gulf of California.

As this happens a mid level ridge will amplify over the west
coast with the mid level low retrograding underneath the ridge
forming a rex block. This will push the upper level low over
southern Manitoba east dragging a surface cold front through the
area. Global models are in pretty good agreement with the front
clearing the CWA by Monday afternoon. Rain chance with the front
look pretty good but the precipitation should be pretty light with
embedded thunder. Forecast soundings on the GFS show PWAT values
only around 1.5" while the NAM has PWAT values around 1.8".
Instability along the front is limited also. As the front moves
through the area winds could be breezy as the gradient tightens
and low level winds begin to mix down. This will also be
dependent on how quickly the front moves through. A slightly
quicker passage would allow for daytime mixing and slightly
breezier conditions.

Monday night into Tuesday morning the front will have cleared the
area with surface high pressure nudging east. Lows Tuesday morning
will be in the 40s for the first time since June of 2016.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
A closed upper level low will move across the Great Lakes through
mid week. Energy rotating around the low will eventually allow for
the trough/low to dig down into the Ohio Valley region. The 12z GFS
is more progressive with this feature, keeping it as a trough and
shifting it off the East Coast through the end of the week. However,
the 12Z ECMWF closes off the low and actually retrogrades slowly
west across the Upper Ohio Valley through the end of the week. This
results in some uncertainty in the forecast as we head through next
week. For now, will allow for a few showers across mainly our north
on Wednesday as the better energy transfers down across our area.
Will otherwise maintain a dry forecast through the long term,
although if the retrograding ECMWF ends up being right, some lower
end pops would also be necessary Thursday into Friday but given the
uncertainty, think the best option at this point is to trend toward
a blend. This will lead to below normal temperatures through mid
week with highs mainly in mid to upper 60s. Will then allow for a
gradual warming trend through the end of the week with highs into
the mid 70s by Saturday.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Surface high pressure centered over southeast Canada/Eastern Great
Lakes this morning will gradually move east today. Surface
ridging will extend back into the Ohio Valley, while a mid level
ridge traverses west to east overhead. Clear skies this morning
can be expected. The exception will be at KLUK where some IFR
conditions are forecast due to river valley fog. This should burn
off by 13Z. For this afternoon, some scattered diurnal cumulus
clouds will develop over the western terminals.

For this evening, mid level ridge will move east. Diurnal cumulus
will likely dissipate by sunset, leaving mostly clear skies.

For the overnight period, large scale mid level trough will dig
southeast into the western Great Lakes and northern/middle
Mississippi River Valley. An attendent cold front will accompany
this system at the surface. Showers and embedded thunderstorms are
expected along and ahead of the front, which should make in roads
toward the western terminals between 09Z and 12Z.

OUTLOOK...Showers and embedded thunderstorms will bring MVFR
conditions Monday morning and early afternoon. Breezy west winds
expected on Tuesday with gusts between 25 and 30 knots.

&&

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

&&

$$
SYNOPSIS...Haines
NEAR TERM...Haines
SHORT TERM...Haines
LONG TERM...JGL
AVIATION...Hickman


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