Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 131140

National Weather Service Jackson KY
740 AM EDT Tue Mar 13 2018

Issued at 738 AM EDT TUE MAR 13 2018

Issued an update to the forecast to input the latest observations
into the grids and trend them into the after dawn hours. The snow
showers have come to an end and so removed them from the forecast.
So touched up the pops this morning as well. A new zfp was needed
for this update.


.SHORT TERM...(Today through Wednesday)
Issued at 322 AM EDT TUE MAR 13 2018

Current conditions across the area feature the last of the snow
showers passing through southeastern Kentucky this hour. With this
will also follow a brief let up in the cloud cover. Will also
expect low temperatures to drop a few more degrees this morning
with the clearing skies this morning. With an upper level low
stuck in the pattern over the Great Lakes and Northeast region,
another wave will slide south over the OH Valley by this
afternoon. Model soundings show quite a bit of instability with
this feature with 100 J/KG in an upslope event pegged for eastern
Kentucky lasting into tonight.

Heading into this afternoon, max temps will round out around 40
across the area. Any precip will likely begin as rain but will
change to snow heading into the evening. Snow at 36 and 37 degrees
cannot be ruled out for this event given the lapse rates on tap
for this event. The one caveat is the lack of moisture for this
event so will expect the heavier precip to hold off till into the
night and confined mostly to the higher terrain to the east. Thus,
by Wednesday morning, will expect up to 2 inches in the far
eastern counties bordering Virginia. There are still some
uncertainties as to how much moisture this upslope event can
utilize so will throw out an SPS for now to highlight the upcoming
event. Wind directions seem to be a favorable directions as well.

One concern with the models is that the mentioned wave this
afternoon is quickly followed by a second more robust wave late
tonight and into dawn Wednesday morning. This may lead to a few
snow showers around dawn on Wednesday morning that can put down a
quick dusting of snow. The question though remains with the amount
of moisture to work with at that time. Expecting little to none
at that time but some uncertainty remains. The last of the
moisture exits by midday Wednesday bringing an end to the
northwest flow as skies clear out by late day.

.LONG TERM...(Wednesday night through Monday)
Issued at 445 AM EDT TUE MAR 13 2018

The models are coming into better agreement aloft through the long
term portion of the forecast. They all depict anomalously deep
troughing through the eastern half of the nation pivoting to the
northeast by the end of the week. Meanwhile, a flat ridge will
approach Kentucky from the west lifting heights for the JKL CWA
into Friday evening. By this time, a batch of energy will be
coming out of the west and closing off over the High Plains with
the ECMWF slower and further south of the GFS/CMC. This mid level
low remains rather weak as it slips east into the Ohio Valley over
the weekend with the GFS and ECMWF continuing their trends and
the CMC further marginalized as it essentially loses this key
feature. The main energy with this does pass through eastern
Kentucky Saturday night with height rises in its wake. However,
the ridging that follows is not all that strong and plenty of
energy will stream through the area in fairly fast flow before
another Central Plains trough approaches and turns the flow to the
southwest. Additionally, the general agreement among the GFS and
ECMWF does break down for the latter part of the weekend through
Monday so that confidence in any particular solution starts to
flag. Given the issues late, and decent agreement through the
first part of the weekend, a blended solution looked reasonable.

Sensible weather will feature drying and quiet conditions through
Thursday evening before a developing warm front scoots over the
area and likely sets up a glide path over our part of the state
for a return of showers by Friday morning particularly in the
south. This boundary holds in place through the first part of the
weekend while a weak sfc low takes shape and crosses through
Kentucky and the central Appalachians into Sunday morning. It
still looks like the best instability will stay south of the area,
but a stray thunderstorm cannot be ruled out from this event. In
the wake of the departing low, high pressure will slide by
through Monday morning before another warm front threatens to
bring more showers to the state late Monday. Temperatures for the
rest of the week will be near normal before climbing to between 5
and 10 degrees above on Sunday and Monday.

Made only minor, point-based temperature adjustments through most
of the period with the exception of Sunday night when a ridge to
valley temp split is anticipated. As for PoPs - limited the low
values to the north of the boundary through the forecast with some
maximizing of them on Saturday as the main focus of the system
passes through the CWA.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)

The snow showers over the area have ended and a few instances of
IFR and below cigs as well as a few MVFR cigs are still hanging
around. After this, will see clearing skies before another wave
will pass through the area this afternoon. This will bring
another round of rain and snow showers lasting through the end of
the TAF period. Will expect another round of MVFR cigs and near
field mins for visibility with these snow showers. Winds will be
on the increase as well with some 20 knot wind gusts out of the
northwest by this afternoon and lasting into tonight.




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