Area Forecast Discussion
Issued by NWS Jackson, KY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KJKL 232100

National Weather Service Jackson KY
400 PM EST Thu Feb 23 2017

.SHORT TERM...(This evening through Friday night)
Issued at 400 PM EST THU FEB 23 2017

South-southwest flow aloft will keep our weather warm through the
short term. Potent trough/low will plow into Great Lakes Region
swinging a trough through the Commonwealth by late in the period.
At the surface, high pressure is anchored over the Appalachians
with a nearly stationary frontal boundary draped from roughly DTW
southwest to STL. Low pressure currently taking shape over the
central plains will march east-northeast along the boundary and
into the Great Lakes by late Friday night. This feature will also
pull a cold front eastward through the region, and into eastern
Kentucky Friday night.

This dynamic storm system could bring a round of severe weather to
our forecast area Friday night. Main threat at this time appears
to be winds, with hail being a secondary threat. Shear is quite
strong with this system as well. Consequently could not rule out
an isolated tornado. Gradient winds will increase across the area
Friday ahead of the system, and from all appearances will become

Main limiting factor to severe weather will be moisture
as dew points struggle to climb to near 60 Friday into Friday
night. Timing of the cold front is also not favorable for severe
weather as it will not enter into our area until sometime just
after midnight. Consequently any nocturnal inversion that develops
will have to be scoured out, though surface gradient winds appear
to be able to do just that, but generally only as the frontal
boundary is approaching. Bulk shear is quite strong with this
system as well, 40-60 kts, with the majority of the shear
realized in the lowest 3 km. Thus the potential for bowing cells
and line segments will be favored. Surface based instability to
support this storm mode is not ideal but does appear to be
sufficient, again mainly just ahead and with the frontal boundary
itself. This has a distinctive QLCS flavor to it and considering
the environment as a whole feel an isolated tornado can not be
ruled out, though features of this type tend to be weaker than
most and short lived. Strong gradient winds mixing down may have
the potential for more damage should they occur. Low wet bulb
temperatures and freezing levels mean hail is a possibility as

.LONG TERM...(Saturday through Thursday)
Issued at 400 PM EST THU FEB 23 2017

The long term portion of the forecast will be active, with several
systems affecting the area. However there remains considerable
uncertainty on the timing, track and strength of a series of short
waves and associated surface lows and fronts that will affect the
area next week.

By 12Z Saturday the cold front which brings our severe weather
threat Friday night will be east of the area, but some showers will
linger across the area mainly during the morning. Gusty west winds
will usher in cooler air on Saturday, with lows by Sunday morning
expected to dip down into the mid to upper 20s.

Surface high pressure will be over the area Sunday morning, but will
shift to the east during the day. This result in dry weather Sunday
with near normal afternoon temperatures in the upper 40s to lower

The mean flow for the first half of next week will be southwesterly
with a mean long wave trough axis centered over the western part of
the country. This will result in warming temperatures with highs
back in the 60s for Tuesday and Wednesday. The first in a series of
short waves looks to affect the area from Sunday night into Monday,
with rain shower chances increasing from Sunday night into Monday.
If precipitation moves in quick enough Sunday night a few flakes of
snow could mix with the rain before changing to all rain quickly by
Monday morning.

Tuesday still remains one of the least certain days of the forecast,
with the GFS quickly moving out Monday`s system, while the ECMWF
points to lingering rain chances for Tuesday. We will continue to
follow the blended forecast for Tuesday which maintains rain chances
but with probabilities generally lower than on Monday. There is
better agreement that a stronger short wave, surface low and
associated cold front will bring a better chance of showers and
thunderstorms on Wednesday. In fact we will be be going with likely
rain probabilities Wednesday. After the cold front passage cooler
air will spread into the area Wednesday night and Thursday.


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

Seeing isolated reports of marginal MVFR CIGS. Exception being
SYM which is under a band of considerably thicker cloud cover.
This band is pushing northward and should be north of SYM by
around 19Z. Elsewhere CIGS should lift a bit more with afternoon
heating. Seeing some decent CU developing across our southwest but
not seeing anything on radar yet. Forecast soundings suggests a
cap may be building across the area that would otherwise help
retard development. However, could not rule out a renegade shower.
Looking at VFR conditions for the remainder of the forecast
period. Winds will be the main challenge as gradient winds
increase ahead of an approaching cold front. Maintained some non-
convective LLWS for our valley sites through the predawn hours as
a southerly jet begins to increase across the area just above the
boundary layer. Winds will continue to increase through the day
Friday as the nocturnal inversion mixes out. In addition, winds
will become gusty through the afternoon. May have underplayed
gusts just a bit for late in the period but forecast soundings
suggest the greater threat for highest gusts was beyond the TAF
forecast period, or after 18Z.





AVIATION...RAY is the U.S. government's official web portal to all federal, state and local government web resources and services.