Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 200258 AAA

National Weather Service Jackson KY
1058 PM EDT Mon Mar 19 2018

Issued at 1058 PM EDT MON MAR 19 2018

Based on current radar trends, decided to go ahead and remove
thunder from the forecast for tonight across eastern Kentucky. An
updated winter weather advisory has also been issued along with an
updated hazardous weather outlook, which was to remove mention of
thunder for the rest of tonight. The forecast in general was in
good shape overall, but did decide to slightly increase
precipitation probabilities for a few areas tonight, but nothing

UPDATE Issued at 733 PM EDT MON MAR 19 2018

The forecast in on track so far this evening. The latest obs have
been incorporated into the forecast grids to establish new trends.
No update required at this time.


.SHORT TERM...(This evening through Tuesday night)
Issued at 5PM EDT MON MAR 19 2018

Deep surface low pressure near the western tip of KY late this
afternoon will move east across the state tonight. Showers and
thunderstorms were ongoing ahead of the system, and will move east
with it tonight. Elevated instability supporting thunder is
expected to be limited to our southern counties. The initial
precip will move largely move east out of the area late tonight,
with a general lull lasting into Tuesday. Coastal surface low
development will take over, and the supporting upper level trough
will deepen over us on Tuesday and Tuesday night. This will result
in a large area of light precipitation developing and moving into
our area from the west on Tuesday and lasting through Tuesday
night. It should start as rain, but as cold air advection
continues on the back side of the large coastal low, a change to
snow will occur on Tuesday night into Wednesday morning. It will
take some time for temperatures to get down near freezing, and
this will obviously affect how much accumulation can occur.
Current forecast is for 1 to 3 inches for most of the area.
Elevation will also play a role, especially in our southeast
counties. With warm ground and uncertainty of timing of freezing
temperatures, confidence in accumulations is not particularly
high. However, with interoffice collaboration being a factor,
advisories were issued at a fairly early stage.

.LONG TERM...(Wednesday through Monday)
Issued at 406 PM EDT MON MAR 19 2018

The extended portion of the forecast begins on Wednesday with an
active pattern in place over the CONUS. The period begins with a
longwave trough set up over the eastern CONUS as an upper low slowly
exits off to the northeast. During the day on Wednesday, at the
surface, cooler air will continue to filter in from the northwest.
This will keep surface temps cold enough a bit longer for a
longer period of snow before switching back over to rain or a rain
and snow mix. Model sounding lapse rates indicate snow may be
occurring at a warmer temperature, perhaps 33 to 35 degrees. With
the ground being pretty warm and the snow falling during the day
as well, expecting a while for significant accumulation to occur.
Thus, expecting around an inch in the valleys for Wednesday
morning with more expected on the higher elevations even lasting
into the early afternoon. Northwest winds engaging on the back end
of the low Wednesday evening into Wednesday night will lead to
some upslope snow showers lasting into Wednesday morning. With
some instability in the soundings another few tenths of
accumulation is possible for Wednesday night. At this time, ground
temps and critical surface temps will drastically affect the
amount of snow accumulation during the day on Wednesday and even
into the evening and Wednesday night. There definitely are a few
uncertainties to iron out.

After this event, high pressure moves in from the northwest
allowing for a break in the active weather as clearing skies and
dry conditions will persist through the day on Thursday and into
much of Thursday night. In fact the clear skies and cold air
moving in from the northwest will allow for a ridge to valley
temperature difference both Thursday morning and Friday morning.
Lows will be in the mid 20s. For Friday, some uncertainty will
certainly be in the forecast as a disturbance moving in from the
northwest seems a bit starved for moisture and rain chances will
be low at this time as it seems the only chance arrives into the
southwest. By Friday night, a stronger low develops in the Plains
pushing a warm front eastward into the OH Valley, bringing a
better chance of showers to the area. The warm front setting up
across the area by Friday night will linger through Saturday and
Saturday night. The one uncertainty at this point will be any snow
chances. It seems that the only change over will be during the
overnight hours but accumulation will be little to none at all
from Friday through Saturday night.

The front lifts north by Sunday as some showers will linger with
with the passage of the cold front. At this point, it is difficult
as to how far north the warm front will lift so that all of
eastern Kentucky will be in the warm sector. For now, will leave
showers in the forecast for Sunday and Sunday night.


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

VFR conditions will be the rule at the TAF sites for the first
couple of hours of the period. After that, rain showers, and
perhaps a few thunderstorms, will begin affecting SME and LOZ. By
4Z or so only rain showers should be affecting LOZ and SME. The
rain is expected to reach SYM and JKL between 2 and 3Z, and SJS by
3 or 4Z. This first round of rain should be ending at LOZ and SME
by 5Z. Isolated showers are expected to linger near JKL, SYM, and
SJS through the end of the TAF period after the initial wave of
more widespread rain moves through. Once the rain begins, MVFR to
IFR CIGs can be expected at the TAF sites from time to time. Winds
will be light and variable through early Tuesday morning before
becoming west at 5 to 8 mph across the area. BKN to OVC cloud
cover is expected to prevail through out the period as well.


Winter Weather Advisory from 11 PM Tuesday to 8 PM EDT Wednesday
for KYZ044-050>052-058>060-068-069.

Winter Weather Advisory from 2 AM to 8 PM EDT Wednesday for

Winter Weather Advisory from 10 PM Tuesday to 8 PM EDT Wednesday
for KYZ087-088-118-120.



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