Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 011144
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
744 AM EDT Sat Oct 1 2016

.UPDATE...
Issued at 744 AM EDT SAT OCT 1 2016

Light showers/virga continue to develop across central Kentucky,
but tend to be diminishing in intensity as they move into eastern
Kentucky when farther displaced from forcing aloft. Still possible
to see some of these across the Bluegrass region through the
Interstate 75 corridor later today with diurnal heating.

&&

.SHORT TERM...(Today through Sunday)
Issued at 346 AM EDT SAT OCT 1 2016

Upper low continues to slowly propagate north, now located just
about directly over Cincinnati. This will keep isolated shower
chances confined to the Bluegrass region down toward Lake
Cumberland as upper forcing continues to depart off toward the
lower Great Lakes today. Thunder chances still looking anemic
with surface-based instability of perhaps a couple hundred J/kg
complete with a stout temperature inversion near 700 mb.
Increasing heights/thicknesses and warmer air advecting in on
southwesterly flow will be somewhat offset by increasing cloud
cover rotating into the region this morning and afternoon, keeping
high temperatures in the mid 60s to low 70s.

Weak surface ridging will build north tonight across southeastern
Kentucky, allowing for another appreciable ridge/valley split as
valley temperatures dip into the upper 40s with ridgetops
remaining in the low-mid 50s. Shower chances will continue as
energy skirts around the southern flank of the upper low riding
through the southern Great Lakes. Valley fog will also be in the
offing, especially across southeastern Kentucky where quicker
clearing will take place.

Sunday will offer up one final day of isolated showers, mainly
north of Hal Rogers Parkway/Highway 80 in closer vicinity to any
impulses which may clip eastern Kentucky. Cloud cover will slowly
diminish from south to north through the day with warmer air once
again kicking in aloft, allowing for high temperatures to reach
normal values in the low-mid 70s.

.LONG TERM...(Sunday night through Friday)
Issued at 404 AM EDT SAT OCT 1 2016

Strong upper level low will continue to exit to the northeast during
the extended portion of the forecast. This will leave general
ridging across the Ohio River Valley, with surface high pressure
expected to be in control for Kentucky and points northward from
Monday through midweek. Winds will shift from a northerly direction
to more southerly flow by Tuesday as we find ourselves on the
southwest flank of the center of high pressure. This will allow for
better WAA and temperature modification. While highs on Monday will
stay with in the mid 70s, temperatures by Tuesday will increase to
the upper 70s to around 80 degrees, with a slight uptick in humidity
expected as well. Given the strong southerly pull generated from the
soundings, in addition to good mixing this day, went ahead and
nudged temperatures up a degree or two higher in some locations
compared to the Superblend. Similar conditions will be in place on
Wednesday as well with southerly flow still in place.

Meanwhile, a strong upper level low, which will be located across
the far western conus during the day Monday, will continue on a
northeast track, reaching the Canada/North Dakota border by 0Z
Wednesday. This will result in deep upper level troughing across
much of the western and central conus, and decreasing heights across
the Ohio River Valley. The closed low will lose some momentum and
strength, but should continue to push northeastward through the rest
of the work week, with the axis of the trough moving across Kentucky
Thursday night into Friday (given some slight model discrepancies
this far out in the forecast). At the surface, a low pressure system
will follow in the tracks of the upper level low. It should lag
slightly behind the upper level feature, moving into the northern
Dakotas/Canadian border throughout the day Wednesday. The cold front
produced from this system will extend southward the length of the
conus, and should be located across the central plains and into
Texas by Wednesday afternoon. This will be yet another contributor
to the increasing southerly flow across the Ohio River Valley as
this frontal zone approaches.

The cold front should arrive and traverse the state sometime during
the day Friday (once again this differs slightly given the lack of
forecast agreement this far out). However, continuing to note some
large discrepancies in the extent of precipitation associated with
this frontal passage. As the low continues to pull north while the
front pushes eastward, we stray farther and farther away from the
best forcing. GFS run 24 hours ago showed no precip across the
region as the front passed. However latest 00Z run shows a skinny
but defined line along the frontal axis traversing western KY during
the day Friday, but still loses coverage as it makes it into eastern
KY Friday evening/night. Meanwhile, the ECWMF is much faster and
continues to bring a line of precipitation across the entire state
Thursday night through Friday morning, exiting east of the state by
18z Friday. Which model is right is yet to be discovered, however
given the strong uncertainty, did not feel confident enough to lean
towards one or the other. Kept with the blend, which resulted in
slight chance pops closer to the ECMWF timeline. Given the weakening
boundary and the lack of any instability in the forecast soundings,
chose to remove thunder wording with the precipitation chances.
Temperatures will be on a decline after the frontal passage, with
mid 70s expected for highs on Friday, but only upper 60s on
Saturday.

During the extended portion of the forecast, we also continue to
track Hurricane Matthew as it approaches the southeast Atlantic
Coast. The GFS is much more progressive in its movement toward the
conus, showing Matthew reaching eastern FL by Thursday and then
riding northward along the coastline through Saturday, before
merging into the upper level trough system Sunday. The ECMWF is a
bit slower and keeps the system well off the Atlantic coast. the
ECMWF actually seems a bit more realistic in its timing/velocity of
movement northward through the weekend. But once again, given the
lack of agreement this far out in the forecast, it is yet to be seen
which solution will be closer to the truth. Either way, this system
and its influence on the weather, should remain east of the state
during the extended portion of the forecast.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 744 AM EDT SAT OCT 1 2016

An upper level low continues to meander across the Lower Ohio
Valley. This will lead to bands of clouds through the period and
the threat of isolated showers, although these should remain west
of all TAF sites. Patchy valley fog will mix out within the next
couple of hours, while stratus/MVFR ceilings persist through mid
morning at LOZ/SME and possibly SYM. VFR conditions will return by
mid-late this morning as southwest winds generally increase to
5-10 knots. Winds will diminish this evening as low stratus
potentially develops near the Bluegrass region toward Lake
Cumberland. With the main concentration of this and any visibility
reductions being centered northwest of all TAF sites, have opted
to leave mention out for now.

&&

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

$$

UPDATE...GUSEMAN
SHORT TERM...GUSEMAN
LONG TERM...JMW
AVIATION...GUSEMAN


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