Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181810 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
210 PM EDT Wed Apr 18 2018

.UPDATE...
Issued at 210 PM EDT WED APR 18 2018

Some cu has started to pop up across north central Kentucky in
the past hour, otherwise skies remain clear across eastern
Kentucky. Some 80 degree readings will be achieved in places, as
temperatures have already climbed into the mid to upper 70s.
Updates will be out shortly.

UPDATE Issued at 1231 PM EDT WED APR 18 2018

Surface low pressure is currently positioned across southern
Illinois, with a cold front aligned to the southwest into central
Arkansas. A warm front is branched to the east, currently
shifting north towards the I-64 corridor. Skies are mainly clear
across Kentucky, with gustier southwest winds engaging.
Temperatures have responded, with readings ranging from around 60
north of I-64, to the lower 70s in the south. Have adjusted some
of the highs up a bit, as readings are running ahead of forecast.
Most locations will see mid 70s, with some upper 70s in places.
The main forecast concern through tonight is the wind. The latest
model data suggests some stronger 925 mb winds in the 30 to 40 kt
range available just along and behind the cold front as it moves
into the western half of our forecast area tonight. Shower
activity will also develop along the boundary, likely aiding in
mixing these winds down to the surface. The best winds look to
occur in the west, with some diminishment as the boundary pushes
deeper into eastern Kentucky towards midnight. Consequently, have
issued a wind advisory for the western half of the area, as gusts
look to peak close to 40 mph. Further east, gusts will range from
30 to 35 mph, so have covered this with a Special Weather
Statement. Updates have been sent.

UPDATE Issued at 756 AM EDT WED APR 18 2018

Mid clouds, most heavily situated along and north of Mountain
Parkway, will scour out from west to east by mid-late morning.
Expect temperatures to quickly warm as this occurs and the
approaching warm front moves through.

&&

.SHORT TERM...(Today through Thursday)
Issued at 423 AM EDT WED APR 18 2018

A warm front will continue lifting through the Tennessee Valley and
into eastern Kentucky this morning as a surface low moves out of the
central Plains into Missouri. Developing cloud cover across central
into eastern Kentucky has mainly remained in the mid levels, around
the 5-7k foot level, as subsidence has held strong by way of weak
ridging. Easterly surface winds ahead of the warm front have helped
to maintain local downslope flow, thus negating precipitation
chances this morning.

Clearing skies this morning will gradually give way to increasing
clouds downstream of an upper low approaching Lake Michigan this
afternoon. Increasing southwest flow on the southern flank of a 1003
mb surface low will promote a quick warmup with temperatures
climbing into the low-mid 70s this afternoon. The pressure gradient
will further increase later this afternoon into this evening as the
surface low tracks along the Ohio River. Additionally, 30-40 knots
of wind will reside beneath a lingering subsidence inversion, adding
to the likelihood of gusty winds through peak heating/mixing this
afternoon and early evening. Have once again hoisted a Lake Wind
Advisory for Lake Cumberland, Laurel River Lake, and Cave Run Lake
as sustained winds will approach or at times exceed 20 mph with
gusts nearing 35 mph at times later this afternoon into early
tonight.

Rain chances will increase this evening along/ahead of the
approaching cold front. Shallow saturation, through about 8k feet
off the surface, will help to keep rainfall amounts mainly below
1/10 of an inch as forcing aloft weakens with time as it phases with
an upper low across the St. Lawrence Valley. Could potentially see a
few snowflakes in the higher terrain near the Virginia border
tonight, but the combination of forcing/moisture currently looks to
lose definition by the time temperatures would become cool enough.

A raw Thursday will be on tap as surface ridging builds into the
Midwest and promotes a cold air advection regime. Upslope flow will
keep low stratus in place for a good portion of the day,
contributing to temperatures likely only warming to near 50
degrees.

.LONG TERM...(Thursday night through Tuesday)
Issued at 325 AM EDT WED APR 18 2018

The models are in fairly good agreement aloft through the long term
portion of the forecast. They all depict the departure of the latest
large upper low off to the northeast on Friday allowing heights to
rebound over Kentucky. Omega block style ridging then works east
from the Plains basically dampening out as it moves into the state
through the weekend as the next upper low takes a more southern
route through the Southern Plains. This latter feature is fastest
to come east in the GFS with the ECMWF lagging and a notch
stronger. The Canadian seems to support the ECMWF`s solution
better at this time step into Sunday morning. This low then fades
out as it slowly works east into the Tennessee Valley and Deep
South to start the next work week. Meanwhile the northern stream
will become more active as a strengthening trough moves into the
Upper Midwest and Great Lakes region leaving eastern Kentucky in
an area of weak mid level flow, almost col-like. Given the model
similarities will favor a general blend solution with little in
the way of adjustments or nudges toward any of the operational
models.

Sensible weather will feature cool high pressure slowly crossing the
region to end this work week and continue into the weekend. From
this a frosty night can be expected Thursday night into Friday
morning. The high will moderate in time with the main aspect
being to hold pcpn at bay for a fairly long stretch of time -
definitely a break from the pattern of the past several months.
We will need to watch the efforts of a southern low trying to work
east and pick up some more Gulf moisture - but at this point it
seems that this system will hold off through the weekend and
potentially into the next week - though the GFS does bring in some
rain by Monday morning with the ECMWF showing less conviction with
its wetting of eastern Kentucky for Monday into Tuesday.

Made mainly terrain based adjustments to the lows most nights
next week depending on the sfc advection pattern. Did also beef up
the PoPs in the far southeast through the start of next week in
line with the midpoint of the ECMWF and GFS solutions.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 210 PM EDT WED APR 18 2018

Generally VFR conditions will prevail through 00z, with southwest
winds becoming gusty. Sustained winds of 10 to 15 kts, with gusts
in the 20 to 30 kt range will occur, especially along and west of
a line from KSYM to KLOZ. A cold front will move through eastern
Kentucky tonight, generally between 01 and 05z. Expect
ceilings/visibilities to lower to MVFR at times with the frontal
passage, along with some shower activity. Winds will shift to the
west behind the front, with wind gusts peaking in the 25 to 35 kt
range. The front will exit overnight, with west to west northwest
winds gradually diminishing. A more solid MVFR cloud deck will
move in after dawn Thursday morning, as an upper level disturbance
moves east across the area. West to northwest winds will likely
turn gusty once again during the day.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 2 AM EDT Thursday for KYZ044-050>052-058>060-
068-069-079-080-083>085-104-106-108-111-114.

&&

$$

UPDATE...GEOGERIAN
SHORT TERM...GUSEMAN
LONG TERM...GREIF
AVIATION...GEOGERIAN


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