Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 161934

National Weather Service Jackson KY
234 PM EST Thu Nov 16 2017

.SHORT TERM...(This evening through Friday night)
Issued at 234 PM EST THU NOV 16 2017

The low cloud deck over the northern part of the forecast area
made an advance south early today, but the southern edge of the
clouds eroded at the same time. The erosion of cloud on the
southern edge of the cloud deck seems to be winning out slowly but
surely. As surface high pressure and some weak ridging aloft
builds into the area tonight, expect mostly clear skies to end up
being the rule across the entire forecast area. Clouds have held
temperatures in the upper 30s in the far north today, with
temperatures rising into the upper 50s in the south. With
clearing expect all areas to fall to near or below freezing
tonight. Any fog tonight will be limited to a few valley
locations mainly near water sources.

On Friday temperatures will warm as surface high pressure shifts
east and winds take on a southerly component. With plenty of
sunshine temperatures will warm to the mid 50s in the north to
the lower 60s in the south.

Sheltered valleys should decouple Friday night, allowing a minimal
ridge valley temperature difference to develop, especially early
and mainly in the east. However as cloud cover increases valley
temperatures will rise late in the night. A warm front will also
lift into the area Friday night in advance of low pressure moving
from the central plains to the mid MS valley. With some lift and
increasing moisture, showers will become possible across the
northwest half of the forecast area by late Friday night.

.LONG TERM...(Friday night through Wednesday)
Issued at 445 AM EST THU NOV 16 2017

The models are in only fair agreement aloft through the entirety
of the long term portion of the forecast. They all start off well
with an amplifying trough sweeping across the Plains and into the
Upper Midwest/Mid Mississippi Valley by midday Saturday. This
amplified, but progressive, system will then punch its way into
and through the Ohio/Tennessee Valleys by early Sunday morning
with the core of the energy running east along the Ohio River. The
GFS is slightly faster and stronger than the ECMWF with this
wave, but they are much closer than they were 24 hours ago. This
has raised confidence in the blended solution for this time frame.
Confidence lowers in its wake, though, as heights will slowly
rebound over Kentucky even as more energy pours into and through
the Great Lakes/eastern Ohio Valley on Sunday. A muddled picture
emerges by mid week in the long wave pattern as energy and strong
waves move into the Northern or Southern Plains depending on the
model. As such, the evolution is still quite up in the air for
this time step and through the rest of the extended, though the
latest ECMWF is in between the faster GFS and slower/southern
Canadian model. Going with the ECMWF idea does bring a closed low
through the northern Great Lakes by Tuesday night with some
limited height falls possible for Kentucky. The Canadian model,
though, tries to develop a closed low over the Tennessee Valley
Wednesday - now completely out of step with the other models.
Accordingly, have discounted this solution and dampened its
influence on the blends in GFE. With that being the case, am
looking at slightly northwest flow for the area from mid week on
but not much in the way of mid level energy affecting Kentucky
- though that is subject to change due to low confidence.

Sensible weather will feature breezy conditions building Friday
night through Saturday considering the approach of the cold front
and its strong parent low nearby. BUFKIT momentum transfer
indicates that winds to 40 mph at the sfc will be possible ahead
of and just behind the boundary as it passes eastern Kentucky on
Saturday afternoon/evening. Have highlighted this potential in
the HWO and will monitor it for potential wind headlines as we
get closer. The front should go through with good soaking rains
along with convective showers and perhaps a thunderstorm. Have not
introduced that threat to the forecast, yet, but the possibility
will need to be monitored with time. Colder air will follow in
the front`s wake for Saturday night and Sunday. Lingering
moisture and upslope flow may bring some mixed pcpn (rain and
snow) to the ridges for a time early Sunday and this will also
have to be watched in future forecasts. Chilly high pressure
stars as the weather maker to start the new work week. This high
will start to move off to the east Monday night and moderate,
while also allowing a return flow of moisture north into the area
from the Gulf. Meanwhile, another sfc low will be moving into the
northern Great Lakes with a weak front stretched down to the
Southern Plains. At this point, it seems that this will not be
able to activate much of the return flow moisture keeping
conditions mainly dry through Wednesday across the area before
another cool high pressure bubble slides into the region from the
northwest. Again, confidence in the latter half of the forecast is
rather low due to model discrepancies at the sfc and aloft after

Did make some fine tune adjustments to low temperatures each night
depending on the flow regimen and potential for inversions/mostly
clear conditions. As for PoPs, kept them high through fropa
Saturday evening before taking them down by Sunday afternoon and
through the rest of the forecast - primarily to remove the
Candian`s input late.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)

An extensive area of overcast MVFR ceilings was across north
central and northeast Kentucky. The area of clouds has been
advancing southeast, but the southern edge has been eroding at the
same time. This makes for a challenging sky condition forecast
for the remainder of the day. Current thinking is that SYM will
continue with an MVFR ceiling for the remainder of the day before
eventually scattering out this evening. JKL and SJS will remain
on the edge of the lower cloud and will likely have broken
ceilings for at least a few hours this afternoon, while SME and
LOZ remain south of the cloud deck and remain VFR. VFR conditions
should prevail across the entire area later tonight and into
Friday. Winds will diminish tonight and some fog will form near
rivers and other bodies of water but is not expected to affect the
TAF sites.




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