Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 211258
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
758 AM EST Sun Jan 21 2018

.UPDATE...
Issued at 757 AM EST SUN JAN 21 2018

Only minor updates were made to blend obs into the daytime
forecast.

&&

.SHORT TERM...(Today through Monday)
Issued at 449 AM EST SUN JAN 21 2018

High pressure over the southeast CONUS coupled with a large area
of deepening low pressure over the southern plains is bringing
milder air northward into our area on southerly winds. There is
also shallow moisture present below a 700 mb cap. Lapse rates in
the moist layer are sufficient for some light showers. However,
model guidance suggests the moisture will decline today and this
evening, with a dry night expected. There could even be some sun
to break through today.

The southern plains storm system is forecast to slowly track
northeast to northern Illinois by late Monday. A cold front
spiraling around the system should reach central Kentucky by late
Monday. Southerly winds will increase as the front approaches,
and some limited sunshine during the day will help to mix some
stronger winds to the ground with gusts to near 30 mph. By late in
the day showers near the front should be moving in from the west.
Weak deep layer instability may also be enough for a few
thunderstorms, with the best shot at this in our southwestern
counties.

.LONG TERM...(Monday night through Saturday)
Issued at 356 AM EST SUN JAN 21 2018

The models are in reasonable agreement with the long wave pattern
for most of the extended period with some smaller scale
differences at times. The period will begin with an upper level
closed low in the Midwest Monday evening. This upper low will
track across the Great Lakes through the night into Tuesday and
then the pattern almost flattens briefly in the wake of the
trough. Then another shortwave dives into the area by Wednesday
before a ridge axis moves out of the plains bringing height rises
back into the area Thursday into Friday. Then another long wave
trough moves into the Plains by early Saturday, with an increased
chance of showers late in the day on Saturday.

The period will begin with a cold front approaching from the west
and this will sweep rain showers across the region Monday evening.
The models continue to come into better alignment on timing and
little edits were needed for this portion of the period. The total
precipitation amounts are expected to remain less than a half inch
for most spots given the progressive frontal passage. The pressure
gradient will tighten up and reasonable low level jet will combine
leading to gusty winds Monday night into Tuesday. The winds could
gust as high a 30 mph mainly in the more open Bluegrass region,
higher terrain, and Lake Cumberland region. In the wake of the
front expect falling temperatures on Tuesday, however, we will not
see the more aggressive airmass changes of late. The temperatures
dropping and forecast soundings suggesting some ice present will
lead to a few rain and/or snow showers on Tuesday. The airmass in
the wake will bring temperatures closer to climate normal values
for this time of year Tuesday into Wednesday. Then temperatures
warm as upper level ridge introduces height rises Thursday into
Friday. Then yet another storm system approaches to round of the
period. Given the drier airmass ahead of this system did cap POPs
at chance for now.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 757 AM EST SUN JAN 21 2018

Mainly VFR ceilings are expected through the period, although
MVFR ceilings or a lack of ceilings may also occur at times. A few
light showers may also occur, especially this morning. Winds will
generally be from the south to southwest at 10 kts or less.

&&

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

$$

UPDATE...HAL
SHORT TERM...HAL
LONG TERM...DJ
AVIATION...HAL



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