Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 241820 AAA

National Weather Service Jackson KY
220 PM EDT Sat Mar 24 2018

Issued at 200 PM EDT SAT MAR 24 2018

The latest band of heavy snow passing through central parts of
eastern Kentucky is coming down hard enough to coat some of the
roads with a quick inch or so occurring on grassy and elevated
surfaces. Much of this is moving through our SPS counties so have
upgraded them to an advisory. Further north heavy snow is adding
up throughout the warned counties, but a slow start to the snow
further east will likely keep them in advisory criteria even as
it comes down heavy for a few hours. Do expect the snow to change
to rain for most places south of Interstate 64 as the heavier pcpn
pushes on to the east. The advisory extension has been issued
along with an update to the zones and HWO. Updated grids through
the evening have also been sent to the NDFD and web servers.

UPDATE Issued at 1135 AM EDT SAT MAR 24 2018

15z sfc analysis shows a complex weather map across the area late
this morning as a compact low pressure center is pushing east
across the state. This is bisecting the JKL CWA with wintery
weather to the northeast of a line from Stanton to Whitesburg and
spring weather southwest. At the weather station near Jackson the
pcpn has switched from snow to rain and back to snow again in the
past hour. The heavier returns on radar, along the warm air
cutoff line, are bringing the snow and when it lets up the warm
air wins out making for just rain. The heavier snow showers are
able to cover the roads with a wet slush making to potentially
hazardous driving conditions for the warned and advised areas.
The area web cams are showing some periodically snow covered
roads along the Mountain Parkway and points north. Additionally,
reports have come in of pockets of sleet and freezing rain along
this wavy changeover line. Temperatures reveal the dichotomy
across this weather divide, as well, with readings in the upper
30s and low 40s generally south of the Hal Rogers Parkway and in
the low to mid 30s to the north. The current state of SPS areas,
advisories, and warnings appear on track, though some of the
higher end snow totals will be tough to capture given its wet
nature, packing, as well as the insolation today. It should still
be quite impactful in the warned areas through the afternoon and
into the evening, though. Winds are exhibiting a fairly uncommon
easterly component ahead of the sfc low helping to lock in the
colder air to the northeast. Have updated the forecast to reflect
the impact that the snow and slow to budge colder temperatures
will have on the afternoon conditions. Also allowed for a bit of
freezing rain and sleet in this messy and changeable transition
zone. Patchy fog will continue to affect the region through the
afternoon, as well. Finally, a potential for thunderstorms will
also develop this afternoon in the southern parts of the area and
have maintained that threat in the forecast grids. These updated
grids have been sent to the NDFD and web servers along with a
freshened set of zones.

UPDATE Issued at 800 AM EDT SAT MAR 24 2018

Precipitation making steady headway east and northeast across
eastern Kentucky. Getting reports of moderate snow around Stanton
and Clay City, but accumulations remain confined to grassy
surfaces. Temperatures will continue to wet-bulb to right around
freezing along and north of roughly a Harlan to McKee line, with
precipitation transitioning to rain from south to north through
the morning into this afternoon.


.SHORT TERM...(Today through Sunday)
Issued at 413 AM EDT SAT MAR 24 2018

Light rain continues to push into the Lake Cumberland region this
morning as a warm front lifts northeast through the mid-Mississippi
Valley toward the Tennessee Valley. The parent surface low will
track from eastern Kansas across the Ozarks, allowing abundant
moisture to stream into eastern Kentucky. Temperatures largely
remain in the upper 30s to lower 40s throughout much of eastern
Kentucky, with a few locales across the Big Sandy region and far
eastern Kentucky sitting in the low 30s as a result of being farther
displaced from the warmer incoming air and still being under the
influence of a residual cold dome on the southwestern fringes of
high pressure. Dewpoints in the Bluegrass region still remain in the
mid 20s, so wet bulb processes will allow for cooling temperatures
this morning once virga/rainfall arrives. This should allow for a
mix of rain and snow with likely all snow for a period into this
afternoon from Fleming to Elliott Counties and perhaps a few points
south and west.

Snowfall accumulations will likely be dampened by antecedent warm
ground conditions and extremely wet snow, evidenced by isothermal
sounding profiles just below freezing. Stout omega profiles,
especially above the boundary layer and right in the dendritic
growth layer, suggest plenty of lift in tandem with forcing for
ascent associated with shortwave energy stretching from the Corn
Belt through the Ohio Valley. Expecting 1.25 to 1.75 inches of
precipitation south of Mountain Parkway with around an inch north
through tonight. River flooding concerns may arise across portions
of the Cumberland River basin as elevated convection may result in
periods of heavier rainfall this afternoon and evening. Snowfall
amounts still look to fall in the 3.5 to 5 inch range along and
north of a Mount Sterling to West Liberty line, with 1-3 inches
south of this and north of a Stanton to Jackson to Whitesburg line.
These will be refined through the day based on thermal profiles. It
is important to keep in mind that a degree or less difference in
temperature profiles could spell the difference between several
inches of heavy/wet snow and cold rain. Nonetheless, even a couple
of inches of snow today may be enough to produce scattered power

After transitioning to mostly rain this afternoon, the snow line
will shift back south this evening into tonight. Precipitation will
taper off from north to south as the upper shortwave trough shears
out and translates across eastern Kentucky before becoming absorbed
with energy across the northeastern CONUS. Surface ridging remaining
centered across Quebec along with rising upper heights locally
will negate a strong push of cold air into eastern Kentucky
tonight as the surface low shifts south and east. This should keep
ridgetops near the Virginia state line from seeing much in the
way if any additional snowfall accumulations this evening and
tonight as precipitation remains mostly liquid. Drier conditions
will prevail Sunday afternoon with temperatures topping out in the
mid 40s north to mid 50s south.

.LONG TERM...(Sunday night through Friday)
Issued at 453 AM EDT SAT MAR 24 2018

Upper level ridging will take hold early Monday through Tuesday,
bringing drier weather into the Commonwealth. A trough will
develop to the west as a surface low pressure system develops.
With the progression of this low pressure, a warm front will set
up over the Great Lakes into the Ohio Valley later on Tuesday.
This southerly flow will usher in warmer, moist air up from the
Gulf of Mexico. As the surface low continues to progress eastward,
a fairly slow moving cold front will move over eastern Kentucky
Thursday. This system will be the main source of precipitation for
the extended period. One thing to note is that the precip for the
forecast period will be all rain due to the increase in
temperatures from the southerly Gulf flow.

There is fairly good agreement in the upper level pattern in the
models, especially early on in the forecast period. But, the GFS
shows higher QPF to the west of the CWA by Wednesday morning
compared to the ECMWF. The GFS QPF ranges from 0.1 to 1 inch,
with higher amounts to the north and west of the CWA. The ECMWF
shows QPF of 0.25 inches in the northernmost portion of the CWA at
this time. The latest trends in the model runs then show the
track of the system southward over the Appalachians as the upper
level trough deepens and progresses eastward. The GFS track is
more southerly than the ECMWF, though, since the upper level
trough is more amplified. This also correlates with the higher QPF
shown in the GFS run. Therefore, confidence is low for the later
portion of the extended. Opted for the Blend for the most part,
with little adjustments in the PoPs moreso for the later portion
of the extended.

Temperatures will be on the increase with the advancement of the
southerly, warm Gulf air. High temps will be in the 60s for the
majority of the period until the passage of the cold front later
Thursday, bringing a decrease in temperatures to end the work


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)

Snow impacts continue for the SYM, SJS, and JKL with VLIFR
conditions at times and periods of heavy snow leading to
slushy/slippery tarmacs through the afternoon. Should see a
changeover to mostly rain late this afternoon with some snow
continuing to mix in along and north of an IOB to PBX line. The
snow line will gradually work back south this evening and
overnight as precipitation tapers off from north to south, while
ceilings and visibilities remain IFR/MVFR through the night.
Additionally, the terminals across southern to southeast Kentucky,
including SME/LOZ may see a few bolts of lightning this afternoon
and evening as some elevated thunderstorms will be possible -
already some pulses are showing up near SDF. Conditions everywhere
improve for Sunday with clear vis and cigs coming up to MVFR.
Winds will be generally northeast to east through the period at 5
to 10 kts with occasional gusts up to 15 kts.


Winter Storm Warning until 2 AM EDT Sunday for KYZ044-050>052-

Winter Weather Advisory until 2 AM EDT Sunday for KYZ058-059-



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