Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 180345 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1045 PM EST Tue Jan 17 2017

.UPDATE...
Issued at 1045 PM EST TUE JAN 17 2017

Showers will exit the far southeast in the next hour, as the cold
front continues to move away, and the low level jet weakens. Only
a few sprinkles or patchy drizzle will remain in its wake. The
next feature of interest is a short wave trough which is currently
rotating through IL/IN. This will move east across the Ohio Valley
through the rest of the night, and looks to provide enough lift
for an uptick in light rain showers across most of eastern
Kentucky towards dawn. Forecast lows look on target, and have
mainly freshened up the hourly temperatures and dew points through
the overnight to account for the latest trends in observations.
Updates have been sent.

UPDATE Issued at 659 PM EST TUE JAN 17 2017

The surface cold front is slowly dropping southeast across our
area early this evening. Plenty of light shower activity is
ongoing across the southeastern half of the area. This looks to
continue over the next few hours, as a low level jet continues to
pump in moisture out ahead the passing surface boundary. The
current forecast has this well in hand, and have only freshened up
the hourly temperatures and dew points into tonight. This did slow
the drop off somewhat into tonight, as winds behind the cold
front remain more westerly, rather than northwesterly. Will take a
better look at the overnight lows in the next update.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 315 PM EST TUE JAN 17 2017

As of mid afternoon, an upper level ridge extended from the
Caribbean and Eastern Gulf of Mexico the north to off the Eastern
Seaboard. Meanwhile, a general area of troughing extended from
Ontario southwest to the Mid MS Valley Region and then southwest
and then south into the Four Corners Region and Northwestern
Mexico. Within this trough, a lead shortwave in southwest flow was
currently moving across the Lower OH Valley Region with a more
significant shortwave trough moving across the MS Valley Region
and nearing the Great Lakes and Lower OH Valley region. Another
upper level low was currently centered over the Southern Rockies
and Norther Mexico. At the surface, low pressure was centered over
the Great Lakes region with the trailing cold front nearing
Eastern KY.

This evening and tonight, the mid level shortwave trough should
progress across the Great Lakes and OH valley area with the axis
of this trough nearing the WV and VA borders by around dawn. The
cold front meanwhile should move into VA this evening. Scattered
to possibly numerous showers will remain possible until the cold
front moves through. Sfc high pressure will begin building into
the area. However, some low level moisture will persist even
behind the cold front and with the shortwave trough axis yet to
cross the area clouds, and isolated to scattered showers or light
drizzle will be possible as the low level flow becomes more
upslope. Behind the front some stratus build down fog will also be
possible. The moisture depth is a bit in question so confidence
in timing or extent of any drizzle is not all that high.

The shortwave trough axis should depart during the morning hours,
and with this so should the threat for any isolated showers or
drizzle. Any stratus build down fog should also diminish. The
upper level ridge axis should approach tomorrow afternoon with
rising heights in the afternoon and evening. However, the ridge
axis will be shifting east of the area Wednesday night. At the
same time, the upper level low will have meandered into the
Central and Southern Plains. Low pressure and an associated warm
front at the surface will begin to approach late and moisture and
isentropic lift will increase across the OH and TN Valley late. An
increase in high clouds is expected late and mid clouds may move
into the Lake Cumberland Region. However, the threat for showers
should hold off until sometime on Thursday. This should allow some
valley locations to experience lows in the low to mid 30s on
Wednesday night, which would be warmer than average for late
January but colder than the past several mornings outside of the
northern counties. Valley fog should also develop, but the extent
is uncertain due to the increase in clouds late.

.LONG TERM...(Thursday through Tuesday)
Issued at 258 PM EST TUE JAN 17 2017

Good model agreement continues into the upcoming weekend. An
active pattern will continue into early next week with several
rounds of showers expected. The added rainfall, combined with
rivers already running high could lead to some high water issues
as we head into early next week. However, confidence on actual
amounts remains low, so will continue to leave out any flooding
concerns into next week. The first round of rain will move in on
Thursday and Thursday night as a shortwave trough pushes
northeast across the region. Good forcing and lift will yield
widespread showers. As the trough exits north on Friday,
conditions will temporarily dry out, especially by Friday
afternoon. Looks like dry weather should last through Saturday,
although models are showing some support for a few widely isolated
showers on Saturday. Moisture is fairly limited and lack of any
significant forcing will keep the chance of rain out of
the forecast for now. If a shower were to pop up, best shot would
be somewhere across central Kentucky. As we head late into
the weekend, chances are increasing of a large cut off low
developing across the deep south, then slowly pinwheeling up the
spine of the Appalachians. This slow moving system could bring an
extended period of rainfall to the area late Saturday night
through Monday night. Depending on the exact track of this system
will determine exactly how much rain we receive. If southeast
downsloping flow prevails through much of the time, it would eat
away at potential rainfall. For now, going to go high on the rain
chances through this period with more of the uncertainty falling
on actual amounts. It certainly looks like it will be a mild and
damp period which has been the theme lately. It looks like a
brief shot of more normal temperatures for January will drop in
by Tuesday, but again this may just be a quick shot before we
start to warm again. Right now, no threat of any wintry weather
for eastern Kentucky through Tuesday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 659 PM EST TUE JAN 17 2017

A passing cold front will bring numerous showers to southeastern
Kentucky over the next few hours. Most of the more concentrated
activity will stay to the east and southeast of the TAF sites.
MVFR ceilings will temporarily raise up to VFR for most locations
following the frontal passage, before ceilings then return to
MVFR and eventually IFR through the overnight. An approaching
upper level disturbance towards dawn, may reinforce a few light
rain showers or drizzle across the area. IFR ceilings will then
gradually improve to MVFR, and eventually VFR from southwest to
northeast, as high pressure builds in. West southwest winds of
near 10 kts, will become more out of the west as the cold front
exits to the southeast. Winds will diminish to around 5 kts or
less by the end of the period.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...JP
LONG TERM...KAS
AVIATION...GEOGERIAN



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