Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 160945
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
445 AM EST Thu Nov 16 2017

.SHORT TERM...(Today through Friday)
Issued at 331 AM EST THU NOV 16 2017

This morning the surface analysis shows a weak and more diffuse
cold front has generally moved east of eastern Kentucky. The
model theta-e gradient magnitude would suggest another front is
west and this is also seen on the surface analysis charts this
morning. This is a little stronger and will introduce more changes
in wind and possibly some temperature differences. The challenge
that has been presented this morning is in relation to the lower
stratus. Behind the first front, we have seen some clearing but
there has been some left over stratus/fog at times. This maybe
tough to clear out until second front moves across the region and
therefore did keep some clouds going and patchy fog through the
morning. The second front has a area of stratus slowly progressing
southward toward at least the BLuegrass portions of eastern
Kentucky. The models have been having a tough time handling this
and leaned toward a combo of NAMnest and HRRR with adjustments.

Later today, the lower stratus will slowly scatter out in the
north as we move toward the afternoon. This will lead to more sun
by the afternoon, but highs will remain in the upper 40s to lower
50s under cold air advection pattern. Tonight, an area of high
pressure will crest across the Ohio Valley as upper level ridge
builds eastward. Given the potential for mostly clear skies this
will lead to a decent shot of ridge/valley temperature splits. The
question will be how much fog do we see in the valleys to
mitigate lower temperatures. Right now will lean toward previous
forecast of upper 20s in the deeper valleys and lower 30s
elsewhere. There could be some freezing fog similar to yesterday
morning, but think similarly this will be more of the heavy frost
scenario.

By Friday, a warm air advection pattern will take hold as surface
high pressure moves east out the region. However, winds will be
more in the way of southeasterly and this will probably lead to
downsloping. Consequently, this will likely lead to lower
afternoon RH values in the mid 20s to lower 30s, but winds will
remain light. The superblend was overdone on the dewpoints and
trended these closer to the adjusted MAV and MET. This will
continue to be highlighted in the FWF. Otherwise, we are looking
at a nice day with some increasing high clouds in the afternoon.
Temperatures are in expected to top out in the mid 50s to lower
60s.

.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
Monday.

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 06Z TAFS through 06Z Thursday night)
ISSUED AT 1241 PM EST WED NOV 15 2017

Most sites are beginning the TAF cycle with MVFR to IFR CIGs and
even some VIS restrictions for fog/drizzle. The latest GOES-16
imagery is showing a good amount of clearing and drier air moving
into portions of western and central Kentucky. Therefore, will
taper the clouds off from northwest to southeast through the
overnight into the dawn hours. Then we will see sites improve to
VFR across the board to round out the period. Winds will remain
light out of the southwest then veering west to northwest through
the overnight into later today.

&&

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

$$

SHORT TERM...DJ
LONG TERM...GREIF
AVIATION...DJ



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