Area Forecast Discussion
Issued by NWS Jackson, KY
FXUS63 KJKL 181845
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
245 PM EDT Tue Oct 18 2016
Issued at 245 PM EDT TUE OCT 18 2016
Saw a sudden increase in clouds due to a Cu field. Made a quick
update to adjust for this temporary feature and to tweak afternoon
highs. Otherwise no major changes to the early afternoon update.
UPDATE Issued at 1011 AM EDT TUE OCT 18 2016
Forecast is pretty much on track. Had to make some adjustments to
hourly temps across our east where valley temps are struggling to
respond, more a result of some low level cloudiness that has
developed over some of the higher terrain than fog. Also tweaked
sky grids a bit to account for the additional cloudiness. Any
adjustments to the grids were not significant enough to warrant
an update to the zones at this time.
UPDATE Issued at 629 AM EDT TUE OCT 18 2016
IR SAT showing a mid level deck of clouds streaming into portions
of the region this AM. Other than maybe some patchy valley fog not
much to deal with given the surface high remaining in control.
Overall think the grids are in good shape and little changes were
needed this update.
.SHORT TERM...(Today through Wednesday)
Issued at 340 AM EDT TUE OCT 18 2016
Surface Analysis shows high pressure off the east and we are stuck
in between surface low across the Northern Midwest. This will
establish a gradient across the region today and increasing the
LLJ through the day. This will continue to lead to additional WAA
and we should see our high temperatures maximized today. That said
another potential record setting day with highs in the mid to
upper 80s. The previously mentioned LLJ will also combine with
decent mixing to lead to gusty winds especially across the
Bluegrass and Lake Cumberland region through the afternoon. These
winds are expected to subside through the evening as the mixing
Tonight we will begin seeing an increase in clouds across the
Bluegrass region as a cold front approaches. This could aid in
limiting the temp split tonight, however the usual cold valley
spots will see a drop off early on. While the cold front
approaches by Wed it does stall out along the Ohio River until the
upper level wave moves east out of the plains beyond the short
term period. Therefore most spots will remain dry for Wed, but
areas mainly north of the I-64 corridor will have a slight chance
of a shower and/or thunderstorm in the afternoon. It will remain
well above normal for Wed with temperatures topping out in the low
to mid 80s.
There remains good agreement model wise within the short term, and
therefore was comfortable keeping close to the model blends. One
issue where straying was needed would be max/min temps.
.LONG TERM...(Wednesday night through Monday)
Issued at 400 AM EDT TUE OCT 18 2016
The models are in fair agreement aloft through the extended. They
do start out well matched up as they move a developing trough
through the plains and into the Ohio and Tennessee Valleys by
Thursday night. This sharpening wave will push out the upper ridge
through the Southeast that has been responsible for the record and
near record warmth of the past few days. The trough comes through
eastern Kentucky with a potent band of mid level energy late
Thursday. For this, the ECMWF is running just a tad faster than
the GFS but they are of similar strength. Meanwhile, the Canadian
is much too slow and these problems persist through the remainder
of the forecast so it has been discounted. Once the core of the
trough moves through, the breadth of the lower heights slowly
pass through the Ohio Valley into the first part of the weekend
before heading into New England - allowing the heights to rebound
over Kentucky into the start of the new week. Given the
uncertainty around the initial trough moving through the area, but
reasonableness of the ECMWF and GFS solutions, the blended
guidance looks to be a good starting point.
Sensible weather features the best bet for an end to the dry weather
so far this month as a healthy cold front will move through Kentucky
later thursday with showers and some storms likely. In fact, a few
strong to severe storms will be possible given the instability
ahead of the boundary and decent upper level dynamics associated
with the mid level trough. Will hit this a tad harder in the HWO.
The threat for thunder will continue into Friday, but hold to just
the higher pops as they depart from west to east during the day.
The frontal passage will herald in a colder air mass and with the
clearing to follow over the weekend cannot rule out some frost
patches for the deeper valleys late at night Friday and Saturday.
For now, though, will leave this out of the grids and just monitor
its potential in upcoming forecast packages.
Made some small to moderate adjustments for lows each night from the
CR init throughout the extended primarily to better address
anticipated terrain driven ridge to valley temperature splits early
and late in the period. As for PoPs, basically just tightened up the
highest values around the fropa from Thursday afternoon into Friday.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
ISSUED AT 245 PM EDT TUE OCT 18 2016
VFR conditions expected through the forecast period. Main forecast
challenge has been winds, which have been running between 10 and
20 kts. Gusts have only been 5-10 kts higher. Overall winds are
beginning to shows signs of trending down slightly. Expect winds
will continue to lighten but only gradually through the
afternoon, and not without the occasional spike. Current CU field
will also dissipate gradually as drier air continues to mix out
the boundary layer. However, clouds will be on the increase,
especially across the north tonight as a cold frontal boundary
approaches the Ohio River.