Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 221139

National Weather Service Jackson KY
639 AM EST Mon Jan 22 2018

Issued at 639 AM EST MON JAN 22 2018

WSR-88D radar has indicated a few passing rain showers or
sprinkles across the Bluegrass region this morning. Otherwise, a
line of showers and thunderstorms are just now entering far
western Kentucky this morning. Some of the latest guidance
indicates this line of showers and thunderstorms will diminish as
it moves east toward eastern Kentucky. The HRRR has this line
diminishing but another line of showers developing closer to the
approaching boundary. These trends will have to be monitored and
additional edits will probably be required related to timing and
amounts of precipitation in later updates. These ideas along with
updates to the latest obs have been added to the grids and sent
to NDFD.


.SHORT TERM...(Today through Tuesday)
Issued at 350 AM EST MON JAN 22 2018

The morning surface analysis indicates a warm front to our north
from the Lower Great Lakes into the Midwest. An area of low
pressure is centered near Kansas City with a cold front extending
southward into the Southern Plains. The water vapor imagery
reveals a closed upper level low is located across the Central
Plains. These features will be of interest later this afternoon
into this evening. This morning we are dealing with some mid level
clouds streaming out ahead of this system. This mid level deck
will lift through the morning and lead to a period of just high
clouds late this morning into the early afternoon. This will be
aided by downslope flow ahead of the approaching cold front.

The previously mentioned upper level low will become vertically
stacked as it moves into the Upper Midwest and Great Lakes region.
A lead cold front will move eastward and the model guidance still
shows some disagreement on the timing on the precipitation this
morning. Overall took a compromise between the guidance products,
and did back away some from 100 POP given some guidance shows
weakening of the precipitation as it moves east. Despite this,
there remains the potential for gusty winds ahead and behind this
front. It looks like winds of 25 to 30 with isolated gusts up to
35 mph are possible this afternoon and evening. Given the more
isolated nature of the 35 mph gusts will hold off on a lake wind
advisory for the Lake Cumberland, Laurel River Lake and Cave Run
Lake regions at this time. The other hazard this afternoon and
evening will be the chance for thunderstorms. The wind shear will
be unidirectional but quite strong, However, the lack of more
substantial instability will keep these storms tame.

The rest of tonight into Tuesday will be in the process of a
slight cool down. Matter of fact, tonight will probably be a
midnight high temperature for Tuesday and falling temperatures
there after given the lingering trough and clouds. We never get
into a stronger northwest flow and remain more westerly, so the
temperature drop will not be the extreme drops that we have seen
in the past few weeks. There will be some left over moisture and
this will translate into showers Tuesday mainly in the far east
and southeast. There remains some question on if we will see any
snow mix into these showers, as the model soundings conflict on
how much ice will be present. Given this did limit the mix of snow
showers in the higher terrain in the southeast and otherwise kept
this all rain showers for now.

.LONG TERM...(Tuesday night through Sunday)
Issued at 414 AM EST MON JAN 22 2018

A few showers may still be ongoing as the period starts, occurring
in upslope cold air advection on the southwest edge of a large
storm system departing to the northeast. They could be in the form
of rain or snow, with surface temperatures being marginal, and -10C
moisture aloft necessary for snow also being marginal. The storm
system departs by Wednesday, but a shortwave trough could result
in additional snow showers or flurries, especially in the northern
and eastern portions of the forecast area. Even though high temps
could push 40 on Wednesday, any precip would likely be snow due to
low surface dew points and cold air aloft. This departs Wednesday
night, and surface high pressure builds in from the west, followed
by ridging aloft, resulting in dry weather and warming temps to
finish the work week.

During the weekend, another progressive upper trough moves in
along with a surface cold front. Models are still showing some
differences in timing, and POPs for showers are being held to the
likely category. At this point, the highest POP looks to be late
Saturday and Saturday night. A categorical POP may be in order
once the timing is more certain.


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

The TAF sites are starting off the morning VFR and this will hold
till this afternoon and evening timeframe. A strengthening low
level jet will develop today ahead of a cold front and upper level
trough. This will lead to LLWS through late morning. A tightening
pressure gradient will also lead to gusty winds this afternoon and
tonight, with gusts out of the south to southwest at 25 to 35 mph
at times. A cold front will head toward and cross the region this
afternoon into tonight and bring a chance of showers and
thunderstorms. This line of showers and thunderstorms will lead to
periods of MVFR for CIGs and VIS this afternoon and evening.
These will subside and only showers will remain in the wake, and
the guidance indicates CIGs will improve to VFR.




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