Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 202119 CCA

National Weather Service Jackson KY
519 PM EDT Tue Oct 20 2020

.SHORT TERM...(This evening through Wednesday night)
Issued at 518 PM EDT TUE OCT 20 2020

Amplified flow remains in place across the CONUS. Prominent
ridging continues to reside along the western Atlantic, as well
as the eastern Pacific, while broad troughing rules within the
center of the country. At the surface, a strung out quasi-
stationary frontal boundary remains positioned from northern New
England down through the Ohio Valley and into the southern Plains.
High pressure is centered across southeast Ontario, as well as
the northwest Atlantic. Ridging extends southwest from this center
across the Mid-Atlantic region and through the lower Mississippi
Valley. Dry weather has returned to eastern Kentucky this
afternoon, as 925-850 mb moisture transport weakened and shifted
north with time. Skies have cleared out across southeastern
Kentucky, with partly to mostly cloudy skies hanging in across the
northwestern half of our area. Despite the clouds, temperatures
rebounded nicely today, with most places seeing low to mid 70s,
with a few upper 70s noted, where clouds had thinned a bit

Dry weather with above normal temperatures will be the rule
across eastern Kentucky through the short term. The western
Atlantic ridge will expand higher 500 mb heights in across the
southern and central Appalachians through Wednesday, before
relenting a bit more into Wednesday night, in response to
short wave energy digging in across the Rockies. At the surface,
high pressure will remain positioned across the southern and
central Appalachians. This will result in mostly clear skies, with
temperatures averaging around 10 degrees or slightly more above
normal for this time of the year.

Clearing skies will continue to build in from the southeast
tonight. Light southerly flow will promote a modest ridge/valley
temperature split, with valleys seeing lower 50s, while ridges
stay closer to the 60 degree mark. Patchy fog will also develop
tonight, mainly in the deeper river valleys. Wednesday will
feature mostly sunny skies and temperatures rebounding to the
upper 70s to around 80. Wednesday night will feature a repeat
performance, with skies remaining mostly clear, along with
similar temperatures compared to tonight.

.LONG TERM...(Thursday through Tuesday)
Issued at 436 PM EDT TUE OCT 20 2020

At the beginning of the forecast period our area sits under the
influence of ridging aloft. A trough centered over top of the
central plains starts to amplify as a wave begins to round through
it. As it progresses eastward on Friday, it starts to erode those
higher heights. The pattern continues to amplify as we go through
the weekend and into the beginning of the work week and the trough
continues its journey east. While this general pattern is fairly
well represented, there is still some disagreement surrounding speed
and intensity.

At the surface, the region still remains under the influence of high
pressure off to our east on Thursday and Friday. The ridging aloft
and the southerly to southwesterly flow around the high helps to
keep things warm through that time frame, with highs generally
staying in the upper 70s to about 80. As we get into Friday
afternoon and evening, a surface low moving northeast from the Upper
Great Lakes into Canada will drag a cold front east across the
Mississippi Valley towards our area. With the support of a moist
airmass and this approaching front, our area sees the beginning of a
decent stretch of rain chances. Through the weekend, some
differences arise regarding how the front is handled. The ECMWF has
been consistent in showing this front stalling just to our north
before eventually lifting out. The GFS had previously been keeping
the front more aggressive and moving further through the area. While
still a relatively more progressive solution, the GFS has trended
toward the ECMWF solution and so have leaned slightly more towards
that direction as well for temps. Going into Monday and Tuesday a
second front is set to impact our area, bringing continued chances
for rain, but there is still considerable disagreement over the
details. With the magnitude of the spread among model solutions and
within ensemble members, have kept closer to the NBM output,
especially regarding temps. However, these are likely to need
adjusting as we move forward in time and models hopefully begin to
converge toward a common solution.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)

Scattered to broken stratocu, ranging from 2-4k feet agl, will
gradually dissipate through this afternoon. KSYM will see the
longest period of MVFR ceilings, before VFR conditions return by
around 21z. Skies will clear out tonight, with some river valley
fog likely seen between 04 and 13z. Have left out any mention in
the TAFs for now, as current model guidance was not too keen on
it. South to southwest winds of around 5 kts this afternoon will
diminish into this evening.




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