Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 192330

National Weather Service Jackson KY
630 PM EST Fri Jan 19 2018

Issued at 630 PM EST FRI JAN 19 2018

Low clouds are quickly moving northeast into central Tennessee.
Models handling this cloud cover poorly at best, but NAM bufkit
soundings are picking up on the moisture associated with this
cloud cover between 900 and 850 mb. Once the clouds move in, looks
like they will be with us for the balance of the weekend. Thus,
opted to go ahead and go with cloudy skies through Sunday evening.
With the increased cloud cover tonight, have opted to put the
lowest temperatures around 05z prior to the onset of clouds. The
eastern valleys should still make a run at the teens, but we will
see a modest temperature rise in these locations through the
second half of the night as the clouds blanket the area.


.SHORT TERM...(This evening through Saturday night)
Issued at 346 PM EST FRI JAN 19 2018

Current conditions across the area feature clear skies over the
region as high pressure centered over the northeastern Gulf Coast
continues to extend a ridge axis northward along the Appalachian
Range. With high pressure shifted east, south to southwest winds
brought some much needed warmer air into the region with
temperatures warming into the low 40s across the area.

Despite this warm up, mainly clear skies will hang on into tonight
and will allow for once again significant radiational cooling the
valleys with a weak southerly flow on the ridges. This will lead
to another night of a significant ridge to valley temperature
difference with valleys in the upper teens and ridges in the upper
20s. By dawn, some mid and upper level cloud cover will roll into
the region as southerly flow increases. Despite the cloud cover,
WAA will be strong enough for temps to warm into the low 50s on
Saturday. Heading into Saturday night, an upper level wave deepens
and ejects into the central Plains as southerly flow increases.
By, late Saturday night a warm front develops and begins to lift
northward. This will bring a chance of showers to the area
Saturday night. Given the low chance, the forecast challenge will
be the fact that forecast soundings are pretty shallow with the
moisture depth. Thus the rainfall onset is certainly in question.

.LONG TERM...(Sunday through Friday)
Issued at 330 PM EST FRI JAN 19 2018

For the extended forecast, the overall pattern has remained
fairly consistent with a zonal to ridging pattern over the weekend
before a system moves in Monday afternoon. The models are coming
into better agreement with timing, especially with the latest
runs. However, the GFS is still ever so slightly faster with the
arrival of the precipitation band. Although, the ECMWF shows a
more stout precip line than the GFS. Furthermore, the ECMWF shows
the incoming trough for early next week more amplified than the
GFS. This could affect exactly how much cooler the temps will get
after the front moves through mid-week. Will continue to monitor
future model runs of the trough pattern in terms of the temps for
later on next week. At the very end of the period, the pattern
will start to shift for another system looking to make its way
into the CWA.

As for the surface, the period starts with an inverted trough to
the east with a surface high pressure system to the south. By
Sunday morning, the winds will become more southerly with a warm
front to the north of eastern KY. This pattern will bring in WAA
and an increase in temps for the weekend. The warm front will
increase chances for some rain showers on Sunday, but the models
are in disagreement on how much will fall. After the cold front
moves through on Monday, surface high pressure will build in mid-
week leading to cooler, drier weather. Towards the end of the
forecast period on Thursday night and into Friday morning, there
is potential for a ridge/valley temperature split due to
light/calm southerly winds and little cloud cover.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)

VFR conditions will continue through Saturday evening, but a deck
of 4-5kft ceilings will spread across the area tonight and linger
through the remainder of the period. Winds will remain light and




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