Area Forecast Discussion
Issued by NWS Wilmington, OH-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KILN 111432
Area Forecast Discussion
National Weather Service Wilmington OH
932 AM EST Wed Jan 11 2017
-- Changed Discussion --Warm and moist air will move into the region this afternoon. Rain
will be possible at times through Thursday, when another cold
front is expected to move through the area. This frontal boundary
will stall in the vicinity, leading to continued chances for
precipitation through the weekend.
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.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Showers near the Kentucky-Tennessee border will continue to move
northeast and track across the forecast area this afternoon. Still
looks like there could be some embedded thunder with this.
Forecast highs look reasonable at this point.
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.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
The active weather pattern will remain quite so through the next
several days, heading into a weekend with the potential for wintry
Continued warm advection tonight through Thursday afternoon will
lead to a continual slow rise in temperatures. As this is
occurring, significant/intense frontogenesis will occur between
two strong areas of surface high pressure. This developing front
will become very well defined by late Thursday morning, extending
from south-central Oklahoma to Lake Erie. The front is forecast to
move east / southeast through the ILN CWA during the afternoon,
with just enough moisture and elevated instability ahead of it to
allow for a brief window where convection could occur. With focused
forcing along the surface front, the greatest chances for
precipitation should be fairly focused, especially as deep-layer
forcing and moisture appear to be somewhat lacking. Dry conditions
are expected immediately behind the front, which is forecast to
pivot to a WSW-to-ENE direction by Friday morning.
A complicated forecast will then set up for Friday and Saturday,
with the surface boundary remaining south of the ILN CWA, leading
to entrenched cool temperatures near ground level -- near or below
freezing during the low end of the diurnal cycle. However, within
the 850mb-700mb layer, flow aloft will remain west-southwesterly
and somewhat warm. The end result will be a strong and saturated
inversion between 950mb and 825mb, with a shallow layer of cold
air below it. This thermodynamic profile is one that would
support, from south to north, the possibility of any of the four
main precipitation types in the ILN CWA -- rain, freezing rain,
sleet, and snow. However, the greatest concern will be the chances
for freezing rain, especially on Saturday morning.
There is reasonable model agreement, excepting the 00Z GFS
perhaps, that most of the ILN CWA will remain dry on Friday.
Precipitation will be focused south of the area, but some light
rain / freezing rain may get into the southern counties during the
morning -- before conditions warm enough to allow for rain during
the afternoon. Remaining stagnantly in a favorable area for lift
with respect to the 500mb/300mb wind flow, precipitation
development will continue to be favored along the low-level
boundary, and on Saturday morning this activity will move far
enough north to allow for more significant precipitation over the
near-surface cold layer. Confidence in the general setup for
accumulating ice on Saturday morning is high, particularly in the
west-central section of the ILN CWA. Confidence in the exact
timing/placement/QPF magnitude is moderate, but confidence in the
exact strength of the warm layer is low -- NAM/ECMWF/GFS
projections show a significant spread in the magnitude of the max
temps through the lowest 3km. This significantly limits the amount
of certainty in the magnitude of the event, and makes any sort of
specific forecast of amounts impossible at this stage of the
forecast cycle. However, there does appear to be enough in the
model/pattern signal to explicitly forecast freezing rain in the
grids, and include a somewhat-generic mention in the HWO.
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Precip may end Sunday when the boundary is shown to sag southward
in response to short wave energy that will tilt the upper flow to
northwest, while surface high pressure builds across the Great
Lakes. Rain may then return on Monday and Tuesday, though the
latest ECMWF guidance points to a drier solution as opposed to
model blends that show persistent precip.
Near normal mid winter highs mainly in the mid and upper 30s are
indicated for Friday and Saturday when an easterly low level flow
will carry cool air. Much warmer than normal temperatures return by
Monday and Tuesday when highs may reach the 50s most locations.
.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
For today, VFR conditions will be short lived. In a
west/southwest flow aloft, a low level jet associated with an
embedded disturbance will result in warm, moist ascent which will
develop/spread showers into the region this afternoon. It looks
like better instability remains to the west over Illinois and
Indiana, but still can not rule out a rumble of thunder. The
probability is about 20 percent, so will continue to leave out of
the TAFs. Models concur that ceilings will lower into the IFR
category with MVFR visibilities in showers. In addition, as low
pressure approaches the western Great Lakes, the pressure gradient
will tighten, allowing winds to increase from the south. Winds
will also become gusty up to 25 knots.
Showers will taper off late this afternoon and evening from
southwest to northeast. Ceilings in the MVFR/IFR category will
remain. Low level jet will increase in speed, which poses another
LLWS threat. This has been placed in the terminals. South winds
will remain stiff and gusty.
For tonight, another embedded disturbance along with low level
moist, convergent flow will spread showers back into the region
from the west/southwest. Best instability appears to remain
northwest of the terminals, although a rumble of thunder may still
occur. Breezy south winds 12 to 18 knots with gusts between 25 and
30 knots will continue.
OUTLOOK...MVFR/IFR ceilings and MVFR visibilities likely Thursday
into Thursday night. MVFR/IFR ceilings and MVFR visibilities are
possible at times Friday through Sunday.