Area Forecast Discussion
Issued by NWS Jackson, KY

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450
FXUS63 KJKL 241909
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
309 PM EDT Sat Sep 24 2016

.SHORT TERM...(This evening through Sunday night)
Issued at 309 PM EDT SAT SEP 24 2016

A strong upper level ridge is in place across across much of the
lower Mississippi and Ohio River valleys early this afternoon,
caught between two upper level closed lows... one off the eastern
Canadian coast, and another more progressive low moving northward
across the Dakotas. Meanwhile another disturbance remains positioned
across much of Florida and the southern extent of the SE gulf
states. This will show little progression through the remainder of
the weekend, staying well to our south and with little impact on the
region`s weather. However, the closed low over the Dakotas will
continue to track northeast today, pushing the associated troughing
pattern eastward toward the Upper Great Lakes by Sunday evening.
This will work to break down the high pressure ridging over time,
though is should still have general control of the Ohio River Valley
during this time.

At the surface, a very weak boundary is pushing southward across the
state this afternoon. This is connected to a surface low pressure
center currently in the Dakotas, being driven by the upper level
low. However with such strong upper level ridging in place, this
frontal passage is dry and overall benign. The only change will be a
deeper northerly post frontal wind component and some continued
diurnal CU through this evening. Strong surface high pressure to our
NE will push into the state behind this frontal passage overnight,
with light winds and strong subsidence expected once more. This
pattern will lead to temperature differences between the ridges the
valleys overnight. Also, any lingering moisture, especially in the
deeper valleys and near bodies of water, will likely lead to more
fog development overnight, with some locally dense spots possible.

High pressure will be in control once again during the day tomorrow
(Sunday). Temperatures will only be a degree or two lower than today
at best, despite the weak cold frontal passage, with such strong
ridging and dry air in place. Meanwhile, the strong surface low will
push into south-central Canada Sunday morning, and continue an
eastward track throughout the day. This will pull with it a stronger
cold front, moving eastward and into the Mississippi River Valley by
Sunday evening, then eventually into central KY to end out the
forecast period Sunday night. Weak southerly flow just ahead of this
line will do little to increase moisture across the region, keeping
best POPs and QPF at bay, especially for eastern KY, through the end
of the forecast period. However, can`t rule out some low end pops
making it into portions of the CWA late in the night. Clouds will be
slow to develop as well, allowing temperatures to be very similar to
that of tonight, with a ridge valley split likely to occur as well.

.LONG TERM...(Sunday night through Friday)
Issued at 335 AM EDT SAT SEP 24 2016

Models have come into much better agreement with the transition from
summer-like to seasonal fall weather during the first half of the
coming work week. This occurs as a deep upper level trough,
currently over Wyoming, splits with its northern piece shifting
eastward and breaking down the upper ridge currently in place over
the Tennessee Valley. The trough and closed low system will dig
southward from the Great Lakes into our area Tuesday and Wednesday,
then may push off the east coast. There are some discrepancies with
how the models handle the closed low beyond the Wednesday time
frame and this could have impacts on how long the cool air sticks
around as well as potential cloud cover. However, there is still
good agreement with the initial transition to cool weather. At the
surface, all models have trended toward the faster and drier
frontal passage solution shown in the past several ECMWF runs.

In terms of sensible weather, summer-like warmth comes to a close
Monday as a cold front approaches the region. Pops increase Monday
afternoon and continue through Monday evening as the front quickly
passes through East Kentucky during the evening time frame. Less
than a quarter inch of rain is generally expected with the frontal
passage, which won`t make much of a dent in the rain deficit for the
month of September. Some lingering showers may be possible along the
Virginia border Tuesday morning but otherwise the area should be dry
by dawn on Tuesday. A much cooler and drier air mass will invade the
region behind the front, with afternoon highs topping out in the low
and mid 70s for the remainder of the work week. Overnight lows will
dip below seasonable values with temperatures ranging from the mid
40s to low 50s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
ISSUED AT 210 PM EDT SAT SEP 24 2016

High pressure will remain in control of our weather through the
weekend resulting in VFR conditions for most areas with light and
variable winds. Some diurnal CU has developed across the CWA,
mainly between 4.5 and 5k ft. These clouds should dissipate with
loss of daytime heating this evening. Patchy valley fog will form again
overnight, possibly affecting SME with some MVFR BR for a couple
of hours late in the night into early Sunday morning. Otherwise
have continued to keep the TAFs to one line.

&&

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

$$

SHORT TERM...JMW
LONG TERM...JVM/ABE
AVIATION...JMW



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