Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 192330

National Weather Service Jackson KY
630 PM EST Mon Feb 19 2018

.SHORT TERM...(This evening through Tuesday night)
Issued at 405 PM EST MON FEB 19 2018

As of mid to late afternoon, a mid and upper level ridge was
centered south of Bermuda with another ridge over parts of the
eastern Pacific. A trough was located over the western Conus and
Rockies with southwest flow aloft. Meanwhile, a baroclinic zone
extended from Quebec into the Great Lakes to mid MS Valley to the
southern Plains. Despite some passing mid and high clouds and
cumulus having developed, with south to southwest flow warmer air
has advected into the region behind a warm front. Temperatures
have reached the low to mid 70s in all but the VA border counties
where clouds have been more extensive. Record highs have been at
least tied so far at both JKL and LOZ.

The ridge located south of Bermuda should build west into the
southeast and eastern seaboard tonight and into Tuesday as a
trough continues to work across the west with a series of
shortwaves moving from the Rockies and Plains to the Great Lakes
and into Ontario. At the surface, the region will remain in the
warm sector during the period, with a sfc wave of low pressure
and an initial shortwave moving into the Great Lakes tonight and
weakening. Another wave of low pressure should develop in the Lee
of the Rockies in advance of the next shortwave tonight and track
into the Western Great Lakes on Tuesday. A more potent shortwave
will move across the Rockies and into the Plains from Tuesday into
Tuesday night, combined with the mid and upper level ridge
building north off of the eastern seaboard, should begin to push
the baroclinic zone/cold front into the Lower OH Valley by the end
of the period. However, with weak forcing at best during the
period, a considerable amount of clouds are expected through the
period though it should remain rain free. However, there have
been breaks in the low clouds today and there may be some breaks
at times through the period.

Cumulus clouds should dissipate tonight with breaks in clouds
expected. Deeper sheltered valleys should decouple this evening
with eastern valleys dropping off well into the 50s with ridgetop
and more open terrain only dropping to around 60. Continued
southerly flow and 850 mb temperatures climbing a coupe of degrees
C should bring record highs for the 20th to both JKL and LOZ.
Depending on the amount of sunshine, the all time February record
high of 79 at JKL from 1996 will likely be broken as the forecast
high is currently 80. LOZ will likely set a record daily high for
the 20th, but fall short of the all time February record high.
Deeper and more sheltered eastern valleys should again fall well
into the mid 50s on Tuesday night.

.LONG TERM...(Wednesday through Monday)
Issued at 254 PM EST MON FEB 19 2018

Model solutions for the extended are in good agreement through
Thursday. There is general agreement in the overall mid/upper level
pattern thereafter but a few more significant differences show up
that will influence any details of sensible weather. The extended
will remain under the influence of southwest flow until the end of
the period when stronger systems riding out of the southwest CONUS
begin to wear down high pressure just off the Atlantic Coast,
causing steering winds aloft to veer more westerly. At the surface
we find a semi-stationary baroclinic zone has set up across the Ohio
Valley. An associated surface frontal boundary will drop down across
our area late Wednesday or Wednesday night. This boundary then
stalls in the vicinity of our area as dynamics driving the surface
system lift northeast into eastern Canada. This boundary quickly
shifts back to the north during the day Friday as a wave of surface
low pressure passes through the lower Ohio Valley and into the Great
Lakes. Several minor waves of low pressure continue to traverse the
region along this baroclinic zone until a final more significant
wave sweeps everything out to our east by late Sunday or early

Sensible weather features generally unsettled and warmer than normal
weather through the extended. There will be some threat of rain just
about anytime through the extended. Temperatures will run some 10 to
20 degrees above normal through the period. The main exception will
be Thursday when the surface frontal boundary stalls and produces a
large temperatures gradient across the area with low to mid 50s in
the north and near 70 across the south. Otherwise high temperatures
will run in the mid 60s to mid 70s on average. Overnight lows will
run generally in the 50s. Temperatures do drop back down much closer
to normal by the end of the period. There does appear to be enough
surface based instability in place across the area to maintain the
mention of thunderstorms on Wednesday with the arrival of the
surface front. There is also a short period of elevated instability
across the area early Friday north of the surface boundary as it
lifts northward. Is it possible meteorological spring arrived a bit
early this year?


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

We will start the TAF period VFR and that will remain the story
for the remainder of the TAF period. However, under warm
southerly flow we will keep at least some high clouds streaming
across the Ohio Valley for the TAF period. The models are in good
agreement on a increasing LLJ across the Tennessee and Ohio Valley
and with an inversion setting up this evening have added LLWS to
the TAF later this evening into early Tuesday. The previously
mentioned LLJ will lead to gusty winds Tuesday afternoon as we see
more mixing. Overall we will be looking at 15 to 20 knot gusts,
but higher gusts are not out of the question.





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