Area Forecast Discussion
Issued by NWS Wilmington, OH

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FXUS61 KILN 242353
AFDILN

Area Forecast Discussion
National Weather Service Wilmington OH
653 PM EST Tue Jan 24 2017

.SYNOPSIS...
Surface low pressure will move northeast into the Great Lakes on
Wednesday, with warming conditions expected in the Ohio Valley.
A cold front will move through the area on Wednesday evening,
with cooler conditions expected for the rest of the week.
Occasional chances for snow showers will exist from Thursday and
into the weekend, with an upper level trough remaining in place
over the eastern third of the US.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
Extensive stratocumulus cloud cover remains in place across the
ILN forecast area today, with the erosion on the southwestern
edge just starting to reach Carroll and Owen counties in
Kentucky. Despite this, there are signs of a shift to warm
advection, as ridging is now building into the area at 700mb.
Surface and near-surface flow will be slower to respond, which
could keep these clouds in place for much of the evening and
into the overnight. However, once the surface low pressure over
Kansas moves into Missouri, an ill-defined warm front will move
north through the ILN CWA, allowing for southerly /
southwesterly flow to envelop the area.

Some weak isentropic lift is expected to begin during the
overnight hours, and some very light rain or sprinkles might
occur at various points during the next 12-18 hours or so
(as depicted by the WRF-NMM/WRF-ARW models). With limited
deep-layer moisture, measurable precipitation is more unlikely
than likely.

Though temperatures were generally kept diurnal through the
overnight, steady to slightly rising temperatures are possible
from 06Z-12Z in the southwestern sections of the CWA.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Deep-layer warm advection will be ongoing on Wednesday, with dry
conditions expected within the warm sector of the low pressure
system moving into the southern Great Lakes region. This will
lead to warm conditions, even with skies remaining mostly
cloudy. The southeastern section of the forecast area may
approach 60 degrees, with middle to upper 50s for most of the
rest of the CWA. 20-25 knot wind gusts have also been included
in the forecast for Wednesday afternoon.

By evening, the low pressure center will be notably occluded,
with a surface cold front extending from the thumb of Michigan
through Indiana and western Kentucky. This front will move east
into the Ohio Valley, crossing the ILN CWA between 22Z-06Z, with
fairly strong model agreement on timing.

With dry air remaining in place, and a relatively unimpressive
convergent pattern with the front, there is little reason to
believe that widespread precipitation will develop. Most models
are pinning any showery development directly to the front,
which helped increase confidence in the timing of the PoPs,
though values were still kept at 40-percent and below. The
12Z/18Z NAM appeared to develop too much pre-frontal
precipitation and was ignored for this forecast. Any showers
that do develop might look slightly convective, but any
instability that develops at the top of the mixed layer will be
relatively shallow, and unlikely to produce lightning. It does
appear that forcing may strengthen somewhat with time, thanks
primarily to support from the associated mid- level low. Because
of this, future forecasts may be able to increase precipitation
chances in the eastern half of the ILN CWA.

A brief dry slot is expected to wrap into the region behind the
cold front on Thursday morning, before mid-level forcing and
cold advection combine with increasing 925mb-800mb RH,
supporting widespread thick stratocumulus development and
scattered showers. Based on the steep lapse rates in the
boundary layer and the temperature profile, most of these
showers should be snow, with the possibility of some rain
showers mixing in during the afternoon (mainly south of I-71).
This activity may continue through Thursday evening and
overnight, and though there are model disagreements regarding
the magnitude of the forcing, the overall setup suggests that
any accumulations will be light (half an inch or less) and
limited to areas receiving heavier or repeated showers.
Soundings do not look particularly squally, at least through
Friday morning.

With the aforementioned steep lapse rates in the boundary layer
on Thursday, some gusty conditions (25-30 knots) are expected
in the deep westerly flow, especially during the first half of
the day.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Temperatures in the long term will be much closer to normal for this
time of year than it has been around the region.  Several weak
disturbances will work through the region Friday through Sunday. This
will lead to widespread cloud cover and isolated to scattered snow
shower activity.

High pressure will then work into the region for Monday and allow
for dry conditions through the remainder of the long term time
period.

Went close to the superblend for this forecast as models were in
general agreement on most of the major features.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
MVFR ceilings across the region will gradually erode from
southwest to northeast overnight. Winds will back to southeast
tonight and then veer to the south after daybreak. Winds will
increase a bit during the day with some gusts as a cold front
approaches. An MVFR deck will overspread the region in the
afternoon in advance of the front. A few showers are not out of
the question late in the TAF period, but probability was too low
this far out in the forecast to include in the TAFs.

OUTLOOK...MVFR ceilings may linger into Wednesday evening. MVFR
ceilings and visibilities possible Thursday through Sunday.

&&

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

&&

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


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