Area Forecast Discussion
Issued by NWS Jackson, KY

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639
FXUS63 KJKL 140554 AAA
AFDJKL

AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1254 AM EST Thu Dec 14 2017

.UPDATE...
Issued at 1254 AM EST THU DEC 14 2017

A surface cold front is closing in on our area, currently aligned
from near KFGX to just west of KBWG. Southwest to west winds of 10
to 20 mph, with gusts of 30 to 35 mph continue to howl. The
strongest winds remain just west of our area; however, a few gusts
to around 35 mph will be possible near and around frontal passage.
Have freshened up hourly temperatures, which continue to run mild
in the low to mid 40s out ahead of the front. The models typically
struggle with this leading edge air mass, and have tried to blend
into the existing curve through the rest of the night. Will stick
with the current lows; although, the low temperatures will likely
be achieved closer to the mid-morning hours. A few post-frontal
flurries still look possible as well.

UPDATE Issued at 915 PM EST WED DEC 13 2017

Increasing and lowering cloud cover continues to invade eastern
Kentucky on the southern fringes of a clipper system pushing
through the Great Lakes and mid-upper Ohio Valley. Gusty southwest
winds will veer westerly and then northwesterly later tonight with
the approach of an associated cold front. A dry near-surface layer
combined with the bulk of any upper support riding north of the
Bluegrass should keep any precipitation, other than a few
negligible snow flurries, north and east of eastern Kentucky
through the night and Thursday morning.

Have let the Red Flag Warning expire as relative humidity values
have increased above 25 percent. Still seeing some sustained
southwest winds of 15-20 mph at times with gusts of up to 30 mph,
so any ongoing fires should be watched closely for erratic
behavior through the night.

&&

.SHORT TERM...(This evening through Thursday night)
Issued at 404 PM EST WED DEC 13 2017

A potent clipper type system was moving southeast across the
Midwest today, headed for the upper Ohio Valley by late tonight.
It is bringing an increasing pressure gradient and warm air
advection to Kentucky this afternoon. An increase in mid level
moisture was resulting in radar returns moving over the area, but
very dry low levels were resulting in virga. Despite the
combination of wind and dry air, verification for the RFW has been
hard to find. Much of the area has seen RH below 25%, but the 20
ft winds above 15 mph have been much more limited so far, and not
coincident with the lowest RH. There is still time for winds to
pick up more by early evening, and the RFW will be left to ride.
If conditions do not materialize, it`s possible it could be lifted
early.

During the night, the clipper system`s cold front will pass
through. With a return to cold air advection, the low levels will
moisten in the upslope flow once again, and low clouds should
develop. If the top of the convective moist layer can reach cold
enough levels, we could see some flurries, but forecast soundings
look marginal for this. Have included a chance in all but our far
southwest counties for late tonight into Thursday morning.

The system quickly departs to the east on Thursday and a weak
surface ridge will build in from the west. Cold air advection will
ease and become more neutral, and the moisture in forecast
soundings become very shallow. We should see low clouds start to
break up, but whether or not the whole area sees it by the end of
the day is uncertain. High clouds will start to thicken during the
day, which would limit sunshine even where low clouds do scatter
out.

.LONG TERM...(Friday through Wednesday)
Issued at 411 PM EST WED DEC 13 2017

The extended portion of the forecast begins on Friday with an
amplified upper level pattern in place with a stout ridge in the
western CONUS transitioning to a trough in the east. On Friday, a
decent short wave passes through the OH Valley but current model
trends keep the majority of the lift and moisture to the north of
the CWA so Friday will remain dry in addition to Saturday as a
weak ridge quickly passes through the area. The upper level
pattern transitions to a more progressive through the weekend
before the next system develops with a stronger shortwave diving
to the south and developing over the lower MS Valley area. This
combined with another wave passing to the north. This set up will
bring a much needed surge of moisture northward with precip
developing into eastern Kentucky by Sunday morning and lasting
into Monday evening.

Concerning the top down of Sunday morning. At this point, surface
temps will be border line for any sleet or freezing rain
development. It appears with surface temps warming up ahead for
this event, will keep a snow and rain mix in the morning hours and
warming quickly into the late morning hours. Thus, will not expect
any accumulation as well. With the drier pattern taking over again
and the main storm track remaining to the north, the last two days
of the extended will likely be dry at this point. This is
especially the case with the outlooks and climatology. The last
half of the extended looks to be at or just above normal as well.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
ISSUED AT 1254 AM EST THU DEC 14 2017

A cold front will move through eastern Kentucky between 06 and
10z. Gusty southwest to west southwest winds of 10 to 15 kts,
with gusts of 15 to 25 kts at times, will shift to the west
northwest through 10z. Northwest winds will then diminish to 5 to
10 kts after 14z. Clouds will gradually lower to MVFR from
northwest to southeast between 08 and 14z, before scattering out
thereafter. Low level clouds will break up by late this
afternoon, with at least some mid-level clouds hanging around
through the rest of the period. A few snow flurries may also be
seen through 15z, but these should not cause any significant
visibility restrictions.

&&

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

$$

UPDATE...GEOGERIAN
SHORT TERM...HAL
LONG TERM...SHALLENBERGER
AVIATION...GEOGERIAN



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