Area Forecast Discussion
Issued by NWS Jackson, KY

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FXUS63 KJKL 231137
AFDJKL

AREA FORECAST DISCUSSION
National Weather Service Jackson KY
637 AM EST Tue Jan 23 2018

.SHORT TERM...(Today through Wednesday)
Issued at 339 AM EST TUE JAN 23 2018

The morning surface analysis shows a cold front pushing across
the region and the low pressure associated with the front pushing
across the Lower Great Lakes region. Meanwhile, an upper level low
pushes on the heels of the surface low as they continue to become
vertically stacked. The Nighttime Microphysics RGB does shows
broken sky cover across far eastern Kentucky with a narrow back of
clearing moving into portions of the Bluegrass and Lake
Cumberland regions. Then behind this another area of stratus will
push east this morning and bring mostly cloudy skies back into the
area through the morning. There is some shower activity early
this morning that will push north and east. Do bring back a slight
chance of showers this afternoon as a surface trough axis and
upper level trough swing toward the area. Overall did keep wind
gusts going in the 25 to 30 mph range at times today as the
pressure gradient remains a factor. Given the cloud cover and
overall pattern the temperatures will drop or remain steady state
through this afternoon.

This evening into tonight a short wave rides around the broad
nearby upper level low. This will also swing a surface trough
across the area. These will combine leading to a few rain and/or
snow showers this evening into tonight. Overall the model sounding
show the moisture just barely getting into the dendritic growth
zone and therefore think the activity will remain light. Did
however add a few tenths of inch to the grids to better match up
to WPC, but again think this will be limited to elevated or
perhaps grassy surfaces. Temperatures dip below freezing for the
first time in several days with lows in the upper 20s.

Wednesday opted to keep sprinkles and/or flurries going through
the afternoon. This as another upper level shortwave drops
southeast and the axis splits eastern Kentucky by 18Z to 20Z.
While the moisture is quite shallow, the model soundings hint at
enough ice to keep flurries going for much of the area. It will
likely remain cloudy through the day and temperatures will remain
in the 30s for most.

The synoptic models have come into better alignment on the
precipitation chances tonight. The short term guidance agrees that
light precipitation moving across north central Kentucky early
this morning will just miss the region and seem to have a better
indication for the potential showers this afternoon. In terms of
clouds in the near term went toward the RUC which seemed to have
the better handle on the narrow band of clearing. The remainder of
the period leaned toward the blended model guidance with edits as
needed.

.LONG TERM...(Wednesday night through Monday)
Issued at 359 AM EST TUE JAN 23 2018

A progressive pattern will be in place during the period. An
upper level trough over the eastern CONUS will be moving eastward
and on the way out at the start of the period, with ridging ready
to move in from the west late in the work week. This too will be
transitory, as another trough ripples eastward across the CONUS,
reaching us over the weekend.

The result for our weather will be dry conditions and moderating
temperatures early on. Both the GFS and ECMWF then show a system
moving in over the weekend, but they do not agree on the timing or
evolution of the system. The GFS shows less amplitude in the upper
wave and is faster. Meanwhile, the slower ECMWF has a deeper upper
level trough and associated surface low development to our south
as the front passes. In light of the differences, will still be
holding POPs no higher than likely category. The overlap of precip
in both models is most prominent on Saturday night, which is when
the highest POP will be placed. There will also be high chance
POPs on either side of this to account for either the slower or
faster scenario. If the ECMWF were to pan out, precip in the
trailing comma head region of the storm system could change to
light snow on Sunday night before it ends. Considering the model
differences which remain, there is not good confidence in the
forecast, and changes can be expected.

&&

.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
ISSUED AT 637 AM EST TUE JAN 23 2018

The TAF sites are beginning the period under VFR conditions, but
latest obs and satellite trends show an area of stratus pushing
eastward across eastern Kentucky. The trend will be for CIGs to
fall to MVFR through the late morning and early afternoon
timeframe. Another round of rain and/or snow showers will be
possible later this afternoon and evening, as another upper level
wave and surface trough axis move across the Ohio Valley. This
could lead to MVFR VIS at times in heavier showers. These will end
late this evening into tonight and CIGs will lift to VFR toward
the end of the TAF period. The tight surface pressure gradient
will continue to lead to 20 to 25 knot gusts through this
afternoon, but these winds will decrease through the evening into
tonight.

&&

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

$$

SHORT TERM...DJ
LONG TERM...HAL
AVIATION...DJ



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