Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 181048

National Weather Service Jackson KY
648 AM EDT Tue Apr 18 2017

Issued at 648 AM EDT TUE APR 18 2017

WSR-88D radar continues to show a few isolated showers or perhaps
sprinkles this morning. Dry air remains in place north of the
Mountain Parkway this morning and therefore could only justify
some sprinkles in those areas. Otherwise little intervention
needed with the grids set this morning.


.SHORT TERM...(Today through Wednesday)
Issued at 349 AM EDT TUE APR 18 2017

WSR-88D does indicate isolated showers continue to move east
across southern portions of the CWA this morning. These seem to be
aligned across a moisture boundary where dewpoint are in the mid
and upper 50s generally south of the Mountain Parkway. Also a high
level jet is exiting east and perhaps providing modest lift as it
does. Most guidance does indicate a upper level wave will move
east out of the Arkansas region through the day. This will
interact with a nearby boundary and increase the chances of
showers and perhaps a few thunderstorms through the day. Does seem
like the guidance would suggest the instability will meager
particularly in the east. The flow will also be
southeasterly/downsloped and this could lead to less overall
coverage in the east as well. That said did keep POPs in the
slight range in the east and northeast, and also keep thunder
limited to the south given little if any support in the MUCAPE

Tonight think the deeper reflection of lift from the upper level wave
will move into the region. Therefore, do go at least chance POPs
area wide by around 4Z to 5Z. Right now limit the thunder to early
evening and wane after. Moisture return will be better on
Wednesday and lingering low level lift will lead to showers and
thunderstorms. Best area for this will be the far east, but the
lift will be fleeting in the afternoon hours based on the omega
sampling seen in the soundings. That said much of the western
portions of the CWA could see little in the way of showers by the
later afternoon hours.

.LONG TERM...(Wednesday night through Monday)
Issued at 418 AM EDT TUE APR 18 2017

The remnants of a shortwave trough will be to our southeast at
the start of the period, but advection of warm/moist air into the
region will persist in the lower levels Wednesday night and
Thursday. No clear focus/forcing mechanism is seen during this
time, but some sparse coverage of showers/thunderstorms can`t be
ruled out. A low pressure system crossing the Great Lakes will
send a cold front south through KY on Thursday night and early
Friday, providing a better shot at getting precip. At this point,
shear does not look too impressive, and the late night/early
morning timing of the system is not favorable for severe weather.

The front is forecast to stall just to our south, and remain close
enough to keep a threat of rain in the forecast Friday and Friday
night, especially in our southern counties. Models are consistent
in developing low pressure along the front in response to an upper
low (currently well offshore of the Pacific Northwest) moving east
in the flow aloft. This system would pass near our area during the
weekend, with our best chance at rain being on Saturday night.
Although models are consistent in developing the system and have
come into better agreement on timing, the track is still shifting.
The trend has been for a more southerly track, and the ECMWF now
takes the surface low by to our south. This would keep our area on
the cool side of the system and limit thunder probabilities. The
GFS still takes the surface low up the Ohio Valley before further
development occurs near the coast. The GFS scenario would bring a
thunderstorms potential, and a mention will still be made in the
forecast, but only in the chance range. With the upper low/trough
not passing over until Sunday night or Monday, showers will remain
a possibility.


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

VFR conditions will be the story to begin the period. The model
soundings still indicate the potential for ceilings to lower to
MVFR as we move into the afternoon. An upper level wave is still
expected to move toward the region and interact with a surface
boundary. This will bring rain showers and perhaps a few storms
as we move into the afternoon hours. The instability still looks
meager and kept the thunder out of SYM/SJS. Winds are expected to
remain light and veer to the SE through the period.




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