Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 162341

National Weather Service Jackson KY
741 PM EDT Fri Mar 16 2018

Issued at 741 PM EDT FRI MAR 16 2018

The forecast is on track so far this evening. Still expecting
widespread cloud cover, rain showers, and perhaps even a few
storms to spread across the area late tonight. Ingested the latest
obs into the forecast grids to establish new trends. Otherwise, no
forecast update is planned at this time.


.SHORT TERM...(This evening through Saturday night)
Issued at 302 PM EDT FRI MAR 16 2018

Low pressure at the surface and aloft was over north central
Kansas early this afternoon. At the surface a frontal boundary
extended east from the low across central Tennessee. The focus of
this forecast will be on this system as the upper low opens up and
moves east across the OH valley on Saturday and the surface low
moves east southeast across Kentucky.

In response to the approaching low the front over TN will lift
north as a warm front tonight before stalling again Saturday.
Showers will develop across our area late tonight. Instability
will be limited tonight but a strong low level jet may support
some elevated convection late tonight as the warm front lifts
north. As such we will include a slight chance of thunder over
the southwest part of the area after 09Z. As the front lifts north
Saturday there will be a break in the rain chances in the
southern part of the area.

Breaks in the clouds will develop across the the south on
Saturday, and surface heating will lead to increased instability
across the south Saturday afternoon. A significant temperature
gradient is forecast across the area as warm advection and a
little sunshine result in temperatures climbing into the upper 60s
and lower 70s in the far south while temperatures remain in the
lower to middle 40s over the far northern part of the area
Saturday afternoon. With the approach of the upper level short
wave trough and the surface cold front Saturday afternoon,
thunderstorms may develop, especially where instability is
greatest in the south and southeast. With decent shear a couple
of storms could be strong or even severe. SPC has placed our area
in a marginal risk for severe storms Saturday, with hail and
strong gusty winds both possible.

As the surface low exits off to our southeast Saturday night rain
chances will diminish from northwest to southeast.

.LONG TERM...(Sunday through Friday)
Issued at 437 PM EDT FRI MAR 16 2018

The main feature to affect the region during the period will be
a large low pressure system tracking from the high plains on
Sunday, eastward across the Ohio/Tennessee valley region Monday
night into Tuesday, and up the east coast later in the week.

Initially, a frontal boundary will be well to our south, and
surface high pressure passing just to our north will bring dry
weather Sunday and Sunday night. As the low heads east, it will
draw the front northward as a warm front, along with gulf
moisture. Showers are expected to develop in response to this on
Sunday into Sunday night. The exact track of the low and resultant
northward limit of the warm front are uncertain, and will be the
main determining factor for our temperatures Monday night and
especially Tuesday. The current forecast is a middle ground of a
wide range of possibility. Model forecasts of instability are
being picked up by MOS, and thunder has been mentioned in the
forecast for Monday afternoon into Monday night.

Along with the coastal development, a significant eastern CONUS
upper trough is forecast to develop, along with a large area of
light precipitation in the cold cyclonic flow on the back side of
the surface low. The GFS and ECMWF are not in perfect agreement,
but both show this affecting our area at midweek. Unusually cold
air is expected, and the rain should mix with or change to snow.
Some light accumulation is a possibility late Tuesday night and
Wednesday, but will be highly dependent on temperatures. At this
point, the best shot at getting snow cover will be over the higher
elevations in southeast KY, but temperatures a little bit colder
than forecast (which is possible) would bring down the elevation
for accumulations. The system pulls out and leaves fair weather
for Thursday into Friday. Cold air advection eases and
increasingly strong March sunshine will work on warming up the air


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

The first several hours of the TAF period should feature SCT to
BKN high level cloud cover. As the night progresses, however, the
clouds will gradually lower and thicken as an area of low pressure
and a frontal boundary approach from the west. LOZ and SME should
begin experiencing rain showers around 9Z Saturday, with JKL and
SYM seeing rain between 9 and 10Z. SJS should finally see its
first rain by 10 or 11Z on Saturday. A few thunderstorms will even
be possible for all the TAF sites but SYM overnight. JKL, LOZ, and
SME should all see a break from the rain from late Saturday
morning through early Saturday afternoon. After that, all five
airports should experience periods of rain showers, and isolated
thunderstorms, during the afternoon and evening hours on Saturday.
A few storms may produce damaging wind gusts or large hail. Low
level wind shear of up to 35KTs will be an issue at the TAF sites
between 12 and 15Z tomorrow. The TAF sites will likely see
fluctuating conditions between MVFR and IFR on Saturday as showers
and maybe a storm or two affect each airport from time to time.
Winds in general should be variable at 5 to 6KTs.




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