FXUS63 KPAH 180939

Area Forecast Discussion
National Weather Service Paducah KY
339 AM CST Fri Jan 18 2019

.SHORT TERM...(Today through Sunday night)
Issued at 338 AM CST Fri Jan 18 2019

Main forecast challenges/concerns in the short term continues to
lie with the storm system expected to affect much of the region
tonight through Saturday evening.

Important note: There is still a considerable amount of model
uncertainty in regards to the winter aspect of this system
Saturday afternoon and evening. Confidence remains low at this
time, especially in locations along and south of the Ohio River.

Widespread moderate to occasionally heavy rains, and even a few
isolated thunderstorms (south areas), will spread east across the
forecast area tonight as strong mid level forcing gets underway
ahead of a potent mid level trof moving east through the southern
Plains/AR region. General rainfall amounts close to an inch to an
inch and a half are expected through Saturday, highest numbers
over wrn KY. With the ground already quite wet, we could see some
minor flooding impacts to creeks, streams and clogged drainages,
especially where the rain comes down hard at times. However,
widespread flooding is not expected to pose an issue, so will hold
off on any headlines at this time.

Bigger questions and uncertainty come into play Saturday afternoon
and Saturday night as the associated surface low moves east
through the mid MS River Valley. Though most models have come into
agreement now on a surface low track through wrn KY on Sat, there
are still differences on how they handle the mid/upper level
dynamics as northern and southern branch trofs interact and try to
possibly phase.

For now, it looks as through there is decent consensus that at
least some type of deformation zone will set up for a few hours
as much colder air sweeps southeast into the region Saturday
afternoon and early evening. If this scenario indeed occurs, we
would have the potential for a couple inches of snow across about
the northern half of the forecast area. Generally less than an
inch would be possible farther south over southern portions of
western KY and MO. However, with rapidly falling temperatures
into the 20s and blustery north winds howling over 30 mph, even
small amounts of accumulating snow could cause some travel
impacts. Given existing uncertainty and the fact that the main
winter impacts are not anticipated until later in the 3rd period
of the forecast, will hold off on headlines with this package and
let the day shift take another look and hone it a bit better. It
is still a somewhat fluid situation given the complexity of the
mid/upper level dynamics. Will issue a strongly worded special
weather statement with this forecast package.

Conditions will become quite blustery and cold Saturday night as
the low pulls off to the east, with temps tumbling into the mid
teens to near 20. Wind chills will likely dip into the single
digits at most locations by sunrise Sunday. As the bulk of the
cold air arrives in force Sunday, high temps at most locations
will not get out of the 20s. It could even stay in the teens to
near 20 up along the I-64 corridor if there is a decent coating of
snow on the ground. Sunday night appears it will be the coldest
night with this outbreak as the surface high moves east over the
Great Lakes region. Most locations will fall well into the teens
by sunrise Monday.

.LONG TERM...(Monday through Thursday)
Issued at 338 AM CST Fri Jan 18 2019

Confidence in the long term portion of the forecast starts off
higher than average with good overall model agreement at the start
of next week. However, confidence drops off by mid week with greater
model variability over the timing of the next weather system.

The core of Arctic high pressure will shift to the east by Monday as
our next storm system approaches from the Central Plains. Flattening
flow aloft and low level southerlies should bring about a decent
moderating trend, with highs on Monday forecast back into the 30s.
The chance for precipitation will increase late Monday night into
Tuesday as the Plains system approaches and makes passage. The bulk
of available guidance indicates a thermal profile warm enough to
support mainly rain during this time. Enough cold air may work in on
the back edge of the precipitation shield to result in a transition
to a period of snow or a mix before ending sometime mid week.

The forecast from Wednesday on is really subject to change at this
point. The model blend hangs on to a small chance of snow through
Wednesday night and Thursday morning. Of the 00Z runs, the CMC is
the only model that supports this, as was the case with its 12Z
predecessor, primarily due to its slower/further west progression of
a secondary southern stream wave. Prior to that, the ECMWF had been
the slow outlier. Within the 00Z GEFS, a quarter of the ensemble
members support a secondary round of wintry precipitation Wednesday
into early Thursday. So while prolonging precipitation chances is
not necessarily the favored solution at this time, it cannot be
completely ruled out. Thus, will maintain the low chances in the
initialized blend for the time being until confidence improves.


Issued at 1043 PM CST Thu Jan 17 2019

Little functional change from the 00z Friday WFO PAH TAF issuance.
Even as a surface low moves into and slightly deepens over
southern Oklahoma near 00z Saturday, the pressure gradient that
would enhance mixing remains generally west of the WFO PAH TAF
sites. The exception would be KCGI, but scattered rain will serve
to keep ceilings near or below 1000 feet agl toward the end of the

For the most part, with light winds in place, fog potential will
be limited through the forecast period.

With limited mixing through the 06z forecast, plan to keep with
the status quo for ceilings with this issuance. Low end mvfr and
upper end IFR ceilings will be the rule.

Should the system over OK speed up, we may see more improvement
into the MVFR category of ceilings for KCGI and possibly KPAH.




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