Area Forecast Discussion
Issued by NWS Jackson, KY

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789
FXUS63 KJKL 261730
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
130 PM EDT Wed Apr 26 2017

.UPDATE...
Issued at 1026 AM EDT WED APR 26 2017

Just updated the forecast to remove mention of fog from the zone
forecast text product, along with any morning or afternoon
wording. The forecast overall is in good shape with no other
changes needed at this time.

UPDATE Issued at 651 AM EDT WED APR 26 2017

Some locally dense valley fog has developed this morning. Updated
to put more areas of fog in valleys. Otherwise, forecast is on
track.

&&

.SHORT TERM...(Today through Thursday)
Issued at 331 AM EDT WED APR 26 2017

Surface and mid level ridge axis will continue to shift east today
with return flow developing across eastern Kentucky. This will
help to usher in some milder weather today with highs into the mid
80s under sunny skies. In the meantime, a potent shortwave vort
max will be digging into the southern Mississippi river valley. A
robust line of showers and storms will develop along a surface
cold front as this wave pushes across that region today. This
activity will then advance eastward tonight. While some weakening
is expected overnight, it may become cold pool dominated and keep
on going through much of the night. If this is the case, this line
of showers and storms could arrive by daybreak into our
southwestern counties, then move across the rest of the area
during the Thursday morning hours. This system will have fairly
good 0-3km shear and this would aid in maintaining the cold pool
as it pushes across the area. The big question is how much
instability will be in play Thursday morning. 00z GFS has some
fairly significant values of SBCAPE, while the NAM has almost
none. The answer may be somewhere in the middle of these two
solutions, as surface moisture may not be as high across the area
as the GFS is suggesting. Regardless, any instability with the
shear involved would aid in the potential for a few damaging
downburst winds. The recent event that comes to mind is the March
1st wind event. However, this time around the low level jet is not
quite as strong, but nonetheless, there will be at least a low end
severe risk through the morning and into the early afternoon
hours. Showers and storms should be done by mid afternoon, with
the evening shaping up to be dry. Temperatures will be a challenge
on Thursday as early day convection may take temperatures down
before a recovery is seen in the wake of the convection in the
afternoon and evening hours.

.LONG TERM...(Thursday night through Tuesday)
Issued at 413 AM EDT WED APR 26 2017

A dynamic and active spring long wave pattern is ahead, as
persistent troughing remains in place across the central CONUS
into early next week. The blended guidance approach mitigates
some of the model differences with regard to the timing and
evolution of the small scale features, so did not stray too far
from the given values.

Short wave ridging will temporarily build in across the region
Thursday night, bringing dry weather. This weekend, a short wave
trough will drop southeast across the Rockies and eventually
cutoff near the Four Corners region and then continue to deepen as
it lifts northeast across the central Plains and eventually into
the Great Lakes. Several short wave troughs will be moving through
the flow, with a warm front aligned into the Ohio Valley, before
a resultant surface low pivots a cold front across the Mississippi
Valley by the end of the week and into early next week.

Friday through Saturday, the better chance POPs look to be Friday
night, as a low level jet ramps up across the area, and the warm
front close by at the surface. At this point, there is too much
uncertainty with the surface evolution and the mesoscale role, to
hone in on a severe threat, so will leave this mention out of the
HWO for now.

The front will be lifting to our north on Saturday, with only a
few showers or storms possible within the warm sector. The surface
cold front will approach from the west Sunday into Monday. Right
now, the best chance for POPs will be Sunday night; however, there
will likely be some forthcoming timing adjustments. Any rain
chances will be on the decrease by Monday afternoon as the cold
front pulls further away to the east. Tuesday looks dry with
heights recovering aloft.

Temperatures will average well above normal through the period,
with highs mainly in the 80s and lows around 60 from Friday
through Sunday. Temperatures will then return to near if not
slightly below normal early next week behind the departed cold
front.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
ISSUED AT 130 PM EDT WED APR 26 2017

Mainly VFR conditions and south southeastern winds at around 10
mph will be seen this afternoon through early this evening. These
winds should shift to a more purely southerly component later this
evening, as a cold front approaches from the west and the pressure
gradient tightens. The winds should continue to increase in
strength overnight, with gusts to around 15KTs possible at times.
BKN to OVC clouds, with bases between 1 and 2K, are expected to
begin overspreading the area around 11Z on Thursday. Scattered
showers and isolated thunderstorms are expected to move across the
area from early Thursday morning through Thursday afternoon. Most
of the rain should be out of the area by the end of the TAF
period. A few storms Thursday afternoon may produce damaging wind
gusts. MVFR conditions will be possible at the TAF sites with any
thunderstorm or intense shower on Thursday.

&&

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

$$

UPDATE...AR
SHORT TERM...KAS
LONG TERM...GEOGERIAN
AVIATION...AR



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