Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 160923
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
423 AM EST Tue Jan 16 2018

.SHORT TERM...(Today through Wednesday)
Issued at 405 AM EST TUE JAN 16 2018

...Accumulating Snow Slowly Spreading Southeast Across East KY...

Early this morning, a trough extended from Eastern Canad south
into the eastern Conus. Within this trough, an upper level low was
centered over the Great Lakes region with a shortwave trough
rotating around it still digging south through the MS Valley.
Further west, a ridge extended through the Rockies with a trough
approaching the U.S. west coast. At the surface, an arctic
boundary continues to sag south and southeast across East KY and
is currently over the southeastern counties. Southeastern valley
locations are generally in the low 30s with teens and 20s over
northeast and Central Ky and some single digits in the west. A
slow moving band of steadier snow that has been moderate to heavy
at times has arrived across the counties north of the Mtn
Parkway. The heaviest snow has been across parts of central Ky
near I 65 south into parts of western and middle TN.

The cold front should continue to slowly sag south across the area
with the slow movement of the boundary and the post frontal band of
snow slow due to the still digging shortwave. However, this shortwave
should begin moving more to the east through this morning with the
through trending toward more neutral. This should lead to the
boundary continuing to slowly move east with a surface wave or two
likely moving along it while deeper moisture persist much of the day
across East KY lingering into the evening in the southeast. Also, a
jet steak moving through the OH Valley to northeast should put much
of the region in deeper lift when combined with the lift from the
approaching shortwave. The forecast soundings trend closer to
becoming isothermal nearer to -10C this morning and into the
afternoon across the south and southeast. Thus, the combination of
this, the deeper lift and substantial omega for a while in the DGZ
will probably lead to higher snow to liquid ratios from later this
morning into this evening and a bit more snow than the previous
forecast. As the shortwave starts to move east and approach, the
steadier moderate to at times heavy snow should continue pushing
south and east, possibly not arriving at the VA border until as late
as 10 AM. The steadier snow should end this morning near I-64 and
north though the steadier snow will persist longer in the southeast,
especially near to the VA border.

With the slower onset and recent model trends of accumulating snow
lingering in the far southeast and near the VA border until late this
evening the end times some adjustments have been made to the end
times of the winter weather advisory. Rowan County has been added a
segment for the bulk of the area through 0Z this evening. Pike,
Harlan, and Letcher counties will experience the latest arriving snow
and latest end to the steadier snow and have been extended until
midnight tonight.

Once the steadier snow departs, some isolated snow showers and
flurries will likely linger through some breaks in the clouds may
continue in the cold advection pattern. Lows for the entire area
should be in the single digits above zero although where decoupling
may occur with fresh fluffy snowpack, a cold spot or two could hit
zero or even a degree or two below.

Low level moisture should linger through the end of the period and
until or a while after the 500 mb trough axis moves through the
region, the threat for isolated snow showers or flurries leading
to some fluffy dusting to half inch amounts will continue into the
day on Wednesday. Highs will be well below normal on Wednesday
with the coldest temperatures in the southeast where the 850 mb
temperatures will be colder through the day and clouds and
isolated snow showers and flurries should be most persistent.

.LONG TERM...(Wednesday night through Monday)
Issued at 304 AM EST TUE JAN 16 2018

The extended period will be mostly dry, with cold temperatures to
start, and then a warming trend expected for the latter part of the
period. Bitterly cold temperatures will persist across the area
Wednesday night through Thursday night, with lows expected to bottom
out in the upper single digits and lowers teens Wednesday morning,
and in from the mid teens to the lower 20s on Thursday morning. The
warm up will first begin on Thursday, as a previously cold air mass
begins to modify after a period of persist south and southwest winds.
Highs on Thursday will only be in the 30s across the area, but most
locations will be above freezing, which will feel quite warm
compared to the bitter cold we will see across the area Tuesday
night through Wednesday night. Friday will mark the true warm up, as
the persistent southerly winds allow the mercury to climb into the
low to mid 40s across the area. The weekend looks to be even warmer,
as mostly clear skies and continued southerly winds allow the air
mass that will be in place to warm even more. Highs on Saturday
should easily max out in the low to mid 50s, while on Sunday we
could see highs ranging from the mid 50s to lower 60s across eastern
Kentucky. The southerly winds and warming conditions will be
harbingers of an area of low pressure that will be our next weather
maker. We could see rain showers moving into the area by early
Sunday morning, as the weather system makes its way eastward across
the region. The showers will be isolated to scattered at first, but
will become more widespread Sunday night and Monday, as a cold front
moves across the area. The latest model data suggests that this rain
will persist until early Monday night before finally exiting the
area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 134 AM EST TUE JAN 16 2018

Snow and lowering ceilings near an arctic boundary should
gradually sag south and east, affecting the TAF sites starting
during the 6Z to 12Z period. Initial VFR at SJS should deteriorate
to MVFR during that time and as the lower atmosphere saturates a
few spots in the north should experience some brief IFR VIS or
CIGS before 12Z with SYM possibly affected by 9Z. The steadier
snow and IFR should begin to slowly exit from northwest to
southeast between 14Z and 21Z. MVFR should then linger behind that
with scattered snow showers for most of the period. Winds should
become NW in all areas through 12Z as the boundary sags south.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 7 PM EST this evening for KYZ052-
058>060-068-069-079-080-083>087-104-106>117-119.

Winter Weather Advisory until 1 PM EST this afternoon for KYZ044-
050-051.

Winter Weather Advisory until midnight EST tonight for KYZ088-
118-120.

&&

$$

SHORT TERM...JP
LONG TERM...AR
AVIATION...JP



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