Area Forecast Discussion
Issued by NWS Jackson, KY-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS63 KJKL 281910
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
310 PM EDT Wed Sep 28 2016
-- Changed Discussion --Issued at 309 PM EDT WED SEP 28 2016
There is a contrast in observed temps dependent on occurrence of
sunshine ahead of the cold front versus clouds/precip behind it.
Have incorporated this into the forecast grids, using the HRRR to
time the boundary southeast through the area late today.
UPDATE Issued at 1112 AM EDT WED SEP 28 2016
Models are in good agreement for this afternoon and evening
regarding precip associated with the cold front and upper low.
Showers and a few thunderstorms will gradually progress into the
JKL forecast area from the NW, but probably only make it into the
far NW part of the area before nightfall. Some further progress is
expected after nightfall, but loss of heating should lead to a
gradual decline in activity. Have updated the forecast for this
UPDATE Issued at 640 AM EDT WED SEP 28 2016
Freshened up the hourly temps to reflect most recent obs. Sent
updates to NDFD and web servers.
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.SHORT TERM...(Today through Thursday)
Issued at 340 AM EDT WED SEP 28 2016
The large upper level low continues to gradually sink southward
from the Great Lakes region towards the Ohio Valley this morning.
The process of this low reaching Kentucky has actually slowed down
a bit in models, delaying further the increase in sky cover and
rain chances this afternoon. In fact, high-res models bring
rain/storms into the far northern counties closer to 21Z. The
models then develop a convective linear feature along the cold
front as it pushes further into our area closer to 00Z Thursday.
The best chances for thunderstorms, including some small hail and
strong winds (with about 900 DCAPE) will likely be contained to
the far northern counties during the late afternoon period. But
since the frontal passage will take place mostly outside of peak
heating late this evening, thunderstorms shouldn`t pose much of a
threat for the majority of the area. Shower chances will then
continue through Thursday evening as the upper low continues
moving over Kentucky. Thunderstorms will again be possible
Thursday afternoon and evening with ample upper level dynamics and
modest instability in the area.
Due to clear skies and dry air in place, lows this morning are
expected to dip into the upper 30s in the deepest valleys and in
the low and mid 40s elsewhere. Even with the dry air in place,
some fog is possible in the deeper valleys and near bodies of
water this morning. Afternoon temperatures should be near average
today, in the mid 70s. But this will depend on how quickly the
cloud cover increases this afternoon. Low temperatures tonight
will be closer to normal (around 50 degrees) with overcast skies
and showers in the area. Thursday will be on the chilly side with
highs only in the low and mid 60s.
.LONG TERM...(Thursday night through Tuesday)
Issued at 326 AM EDT WED SEP 28 2016
A blocky long wave pattern will be in full swing across the CONUS
through the weekend. Starting out, an upper level low will be
entrenched across the Ohio and Tennessee valleys, with ridging
across the Plains, while troughing works in across the West Coast.
The models have maintained fairly good continuity, gradually
shunting the upper level low back to the north towards the Great
Lakes, as the ridge slowly slides east towards the Mississippi
Valley, and troughing becomes more established across the western
CONUS. Model differences in timing and amplitude become more
apparent by early next week, as the trough swings east into the
Cool conditions, along with a threat of some showers, and perhaps
a few storms during peak heating, will continue across eastern
Kentucky to end the work week. Depending upon the exact position
of the cutoff low and an associated dry slot, Friday may be
drier than currently forecast, as depicted by the latest ECMWF.
The last of the showers will end by late Saturday afternoon, as
the low pulls far enough away, and heights recover. Dry weather
will ensue Saturday night and looks to last into early and
perhaps middle of next week, depending on the amplitude of the
ridge. Temperatures will gradually warm up across eastern
Kentucky through early next week, with a few 80s for highs
returning by next Tuesday.
.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 231 PM EDT WED SEP 28 2016
VFR conditions dominated at the start of the period. There were
some diminishing showers moving through the far northern portion
of the forecast area, mainly north of I-64. Much more
precipitation was a bit further to the N & W, from SW OH to W KY.
The precipitation was associated with a surface cold front and a
large upper level low pressure system. The cold front will move
southeast through the JKL forecast area late today and this
evening, accompanied by showers and possibly a few thunderstorms.
Conditions will take a downturn once the precip and front arrive,
with a deterioration to IFR forecast for late tonight and lasting
into the day Thursday. Improvement to MVFR is possible before the
end of the period. Southwest winds will occur ahead of the front
this afternoon, with some gusts near 20kts. Winds will ease behind