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FXUS63 KJKL 170912
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
412 AM EST Sat Nov 17 2018

.SHORT TERM...(Today through Sunday)
Issued at 410 AM EST SAT NOV 17 2018

Early this morning, surface high pressure was centered over the
Appalachians. However, despite the surface high in place, one or
more mid level shortwaves passing by to the north of the area and
some lingering low level moisture generally below 925 mb has led
to stratus or stratocu gradually spreading southeast into the CWA
from OH and the Bluegrass region. This is generally in place at
present near and north of the Mtn Parkway. Meanwhile, fog has
persisted overnight in the valleys with it dens in some locations,
particularly in the Cumberland Valley and Lake Cumberland region.
Per AWOS observations and regional KY Mesonet observations some
of this is likely freezing fog. Overall, the upper level patter
from the Central to eastern Conus is somewhat zonal in nature with
westerly flow aloft as 500 mb heights remain nearly constant. A
general broad upper level trough is in place from the Hudson Bay
region of Canada south and southwest into much of the northern US
from the Rockies east. A more substantial shortwave moving
through this trough is nearing the western Great Lakes with
another shortwave dropping south through the Northern Rockies.

Today and tonight, the shortwave nearing the western Great Lakes
will continue to progress east as well as a couple of weaker waves
in advance of it. At the same time, a shortwave will drop south
and southeast into the Central Rockies and across portions of the
Plains. 500 mb heights should change little this evening before
starting to fall tonight. At the surface high pressure will depart
to the north and east while a cold front pushes south of the Great
Lakes and approaches the OH Valley. A wave of sfc low pressure
moving along the boundary should move into Western KY tonight.
This pattern should lead to a gradual dissipating or retreating
of the low clouds to the north after sunrise with a considerable
amount of sunshine for the area filtered by high clouds today. Fog
and any freezing fog should dissipate through 9 AM or 10 AM
today. On average, temperatures will moderate a couple of degrees
from Friday, but will still remain a few degrees below normal. The
surface high departing to the northeast and warm air advection
pattern tonight will support at least a moderate ridge/valley
temperature split across the east and northeast part of the area.
The pressure gradient tonight will be weak and model time heights
and forecast soundings suggest the atmosphere to be free of low
and mid level clouds.

On Sunday, the surface cold front will approach the area slowly as
a surface wave moves toward the Mid OH Valley. Models remain
consistent with the best moisture and lift along or even behind
the front with forcing focused more aloft versus at the lowest
levels. At this point, it appears that precipitation should hold
off until after sunset on Sunday evening. Temperatures should
moderate further into the 50s across the area.

.LONG TERM...(Sunday night through Friday)
Issued at 338 AM EST SAT NOV 17 2018

East KY will find itself in perhaps one of the more benign patterns
as of late. Light rain is expected to start off the period, but
otherwise, there will be several days with pleasant and
warmer weather on tap.

A cold front will be progressing through the CWA on Sunday night
into Monday morning, with a weakening shortwave moving east out of
the central Plains and across the state during the day Monday. This
shortwave is trending a bit weaker compared to 24 hours ago, but it
will still result in enough energy to produce some light rain
showers through the day Monday across the CWA. Given that most of
the moisture and forcing will actually be along and after the front,
more in line with the mid/upper level wave, this still appears to be
more of an anafront situation. Pops will move east of the region by
daybreak on Tuesday as the front quickly shifts eastward, and the
upper level wave becomes absorbed in the longwave troughing pattern.
Total QPF by the end of the event should generally be 0.2 inches or
less across the CWA. There is also the potential that a secondary
frontal system may move the region on Tuesday afternoon, which could
reintroduce pops briefly during the afternoon. Both the GFS and
ECMWF are starting to come into agreement with this, though coverage
will likely be scattered and precip amounts light.

A large area of high pressure to our west will shift eastward and
encompass Kentucky by Tuesday night. The longwave pattern aloft will
also shift eastward, leaving KY in deep NW flow aloft. This will
result in dry, mostly clear conditions across the region, but will
also continue to promote below normal temperatures Tuesday and
Wednesday. As the area of high pressure slowly traverses eastward
throughout the rest of the workweek, winds will shift to a more
southerly direction, and winds aloft will become more laxed, helping
to boost temperatures a bit higher each day. Highs on Tuesday will
be in the low to upper 40s, but by Friday, highs will be near
seasonal normals in many locations (mid to upper 50s). Meanwhile,
overnight temperatures will take full advantage of radiational
cooling under clear skies and light winds. Tuesday night into
Wednesday morning will be the coldest (especially in the valleys),
with lows in the upper 20s to low 30s. These temperatures will also
slowly moderate through the remainder of the workweek, but do expect
ridge/valley differences each night as was highlighted in the
forecast.

Another area of low pressure will develop and gain strength across
the Northern Plains on Friday, as a trough begins to deepen aloft in
the same area. This system will quickly progress eastward, bringing
us our next chance for rainfall Friday night into Saturday. There is
still quite a bit of uncertainty with this system this far out in
the forecast, so stuck with the Superblend for pops and QPF at this
time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
ISSUED AT 120 AM EST SAT NOV 17 2018

The southern edge of an MVFR cloud deck continues to expand slowly
southeast and at this point expect it to reach near KJKL and KSYM
toward 9Z and remain in those areas for about 3 hours before
retreating north after sunrise. Further cooling overnight should
lead to some of this lowering into the IFR range along and north
of I 64 for a few hours. The lower ceilings should break up or
retreat north and east between 12Z and 16Z. Along the larger
creeks and area rivers, valley fog has developed with IFR vis if
not vis below airport mins in some locations. This is affecting
KI35 and K1A6 and other valley locations. However, at this point
vis should be in the VFR or MVFR range for lighter fog at the TAf
sites. All the fog should dissipate by 15Z. Once the low CIGS and
and fog dissipate by the 15Z to 16Z period, VFR should then follow
for the remainder of the period with high pressure dominating.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...JP
LONG TERM...JMW
AVIATION...JP
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