Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 130550 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1250 AM EST Wed Dec 13 2017

.UPDATE...
Issued at 1235 AM EST WED DEC 13 2017

The current forecast is on track for a chilly morning with a west
to northwest wind adding to the chill. Outside of Black Mountain
wind chills will well stay above zero through dawn. Did update
the T and Td grids through the rest of the night per the latest
obs and trends. also cleared out the sky cover even more based on
the latest obs and satellite images. These minor updates have been
sent to the NDFD and web servers.

UPDATE Issued at 1031 PM EST TUE DEC 12 2017

Tweaked temperatures down a couple more degrees tonight given the
degree of both dry air and clearing filtering into eastern
Kentucky. Expect lows to generally bottom out in the mid teens to
near 20 degrees by daybreak Wednesday.

UPDATE Issued at 652 PM EST TUE DEC 12 2017

Radar continues to show some light returns across portions of far
eastern and northeastern Kentucky. However, dewpoints crashing
into the single digits will likely result in any snow shower
activity remaining as virga early this evening before exiting the
Commonwealth. Clearing skies underneath the influence of surface
ridging approaching from the west will lead to a cold night with
temperatures bottoming out in the mid teens to lower 20s. While
isolated slick spots will certainly be a possibility this evening
and tonight, feel that the threat is far too limited to warrant
any headlines given the degree of drying. This drying influence
will be further exacerbated by ongoing gusty winds for the next
couple of hours until the pressure gradient relaxes.

&&

.SHORT TERM...(This evening through Wednesday night)
Issued at 352 PM EST TUE DEC 12 2017

Scattered snow showers were ongoing over the eastern portion of
the forecast area late this afternoon in upslope cold air
advection, but the back edge of the activity was shifting eastward
as drier air advected into the area and the low level moisture
mixed away. The last of the snow should end from west to east this
evening, and no appreciable accumulation should occur. Clouds
were already diminishing from west to east as well late this
afternoon, and this trend will continue through most of the night
as surface ridging builds in from the west and low level cold air
advection eases, and warm air advection begins.

Warm air advection will continue on Wednesday as a potent clipper
type system moves southeast toward Ohio. Mid level clouds will
likely show up at times over the northeast part of the forecast
area, but dry low levels should prevent any precip. The low will
pass to our north on Wednesday night, and all significant precip
associated with the system will be to our north. However, the
trailing cold front will bring another quick burst of colder air
to the region beginning late Wednesday night. Once again, low
level lapse rates will steepen, and forecast soundings suggest
that the top of the shallow, moist convective layer may reach
temperatures cold enough for ice production overnight over the
northeast part of the forecast area. A low POP for snow showers
will be included there.

.LONG TERM...(Thursday through Tuesday)
Issued at 352 PM EST TUE DEC 12 2017

The extended portion of the forecast begins on Thursday with an
amplified meridional pattern in place. The period begins with the
OH Valley in northwest flow as a weak wave is in the process of
swinging through the area. The next wave passes through the area
by Friday afternoon but stays a tad further north than the
previous. By the weekend timeframe, the pattern seems to become
more progressive and less amplified as the closed low over the
southwest CONUS ejects east into the lower MS Valley, this shifts
east as another stronger wave moves through the Central Plains and
into the Midwest. These features seem to combine over the OH
Valley with the next shot of precip arriving for Sunday and
Monday.

Concerning the lower levels, the waves expected to impact eastern
Kentucky on Thursday and again on Friday, while in upslope flow,
still appear to be starved for moisture. A slight chance of snow
showers will still be on tap for Thursday despite the lack of
moisture but the Friday wave appears to be a tad too far north
with a small chance over the far northern counties. Also expected,
the daytime high temperatures will be a bit too warm for snow all
day so will expect a mix and or change over to rain. A surge of
moisture ahead of the stronger system Sunday evening into Monday
will provide the next best chance for rainfall. As temperatures
cool Sunday night into Monday, a few spots, especially the higher
terrain may change over to snow before changing back to liquid by
the daytime on Monday. At this point, there is little consistency
to pin point any accumulation. Even so, it will be little to none
at this point.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 1255 AM EST WED DEC 13 2017

VFR conditions will persist through the period as high pressure
briefly moves through the area. Look for west/northwest winds
to persist at 5 to 10 kts through the night, before backing
southwesterly and increasing to near 10-15 knots late Wednesday
morning/afternoon as a low pressure system moves toward the upper
Ohio Valley. Gusts Wednesday afternoon could reach 20-25 kts.
Later Wednesday night wind shear looks to be a concern. Will
examine that further for the 12z TAF cycle.

&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...GREIF
SHORT TERM...HAL
LONG TERM...SHALLENBERGER
AVIATION...GUSEMAN/GREIF



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