Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 240057 AAA

National Weather Service Jackson KY
857 PM EDT Fri Mar 23 2018

Issued at 850 PM EDT FRI MAR 23 2018

Hourly grids have been adjusted based on recent observations and
trends for tonight. Clouds are gradually thickening and lowering
from southwest to northeast. With some lower clouds having moved
into parts of south central and middle TN. Some light rain has
been reported as close as KGLW. A few of the eastern valley
locations have experienced few if any mid level clouds so far and
have dropped off to around the 40 degree mark.

Taking a look at the upcoming event, not much in the way of
changes appear to be needed at this time. Looking at 18Z and
recent convective allowing models and making some slight
adjustments to hourly temperatures storm totals generally remained
very similar. Using smaller one hour time steps for snow to
liquid ratios and these hourly temperatures which are a tad cooler
int he north leads to a little less snow for upper end amounts in
northern Fleming, Rowan, and Elliott counties. For locations from
Estill to Letcher, this results in about half of an inch more
snow for Saturday morning. At this time, no changes are planned
for headlines, but each hourly run of HRRR will be evaluated for
any any need for changes. A refreshed WSW product and SPS will be
issued over the next couple of hours.


.SHORT TERM...(This evening through Saturday night)
Issued at 444 PM EDT FRI MAR 23 2018

Extremely complex forecast as low pressure moves out of the
central plains and into the lower OH valley by Saturday evening.
Precipitation type is an extreme challenge as model soundings in
the north show some deep near freezing isothermal profiles, which
may hold through much of the day on Saturday. If such soundings
verify that could mean a very heavy wet clinging snow where even 3
or 4 inches may result in power outage problems. However, it also
means that just a degree temperature difference can result in a
very cold rain. With the trends of recent model runs, WPC guidance
and collaboration with neighboring office have opted to go with a
winter storm warning for our northern counties. Three to 5 inches
of snow is forecast for the warning area, but a few isolated 6 or
7 inch amounts cannot be ruled out. South and east of the warning
we continued the advisory, and also added a couple of counties to
the advisory.

There will be close to a 20 degree temperature spread from north
to the southwest part of the area on Saturday. And further south
some thunderstorms will be possible, mainly in the Cumberland
basin. Latest indications are that rainfall will be spread out
over a long enough time period that small stream flooding should
not be an issue. WPC also has not placed any of the area in the
excessive rainfall outlook. With that in mind have opted to not go
with a flood watch, which we had been considering earlier today.
However, a few points on the Cumberland river could reach flood
stage sometime on Sunday.

.LONG TERM...(Sunday through Friday)
Issued at 111 PM EDT FRI MAR 23 2018

The long term portion of the forecast will feature a deepening
upper level trough over the western U.S. early next week, with
deep southwest flow becoming established across the OH and TN
valleys. By the end of the week the trough will shift east, but
with southwest flow across the eastern U.S. continuing. There is
good model agreement with the overall upper air pattern though
some differences are to be expected with individual short waves
ejecting from the upper low that will be over the southwestern
part of the United States through the first half of next week.

With good model agreement with the overall pattern, the concern
for the coming week will be the potential for heavy rain somewhere
in the central to eastern U.S. with deep southwest flow becoming
established. Current indications are that the heaviest rains will
likely affect areas to our west early to mid week as a slow
moving front moves into the MS Valley. The front will eventually
move across our area during the second half of the week, but it is
possible it will stall again at some point near us or just to our
east. The greatest threat for heavy rains next week appears to be
over western KY and TN. While this is outside our forecast area
it is close enough that the coming week will need to be monitored
closely. Considering the heaviest rain potential is still 5 days
away or so, it is likely the forecast axis of heaviest rains will
shift during the coming days.

The southwest flow will also result in warming temperatures, with
above normal temperatures expected from Tuesday through at least


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

VFR conditions will prevail for the first 6 to 9 hours of the
period, before deterioration to MVFR and then IFR for most
locations after 14Z. The IFR should then persist through the end
of the period as the lower levels saturate leading to low ceilings
with falling precipitation. Low pressure will move from the
central plains to the lower OH valley by Saturday evening. Clouds
will thicken and lower tonight with low level clouds moving into
the southwest part of the area during the next few hours and
advancing northeast ahead of the approaching system. Precipitation
should overspread the area between about 6Z and 13Z. Enough cold
air will remain in place over the northern part of the forecast
area that much of the precipitation will fall as snow or a rain
and snow mix Saturday morning for JKL, SYM, and SJS. Further
southwest just plain rain is expected. Some thunder will be
possible generally after 17Z, mainly at SME and LOZ.


Winter Storm Warning from 2 AM Saturday to 2 AM EDT Sunday for

Winter Weather Advisory from 2 AM Saturday to 2 AM EDT Sunday
for KYZ059-107>110-119-120.



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