Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 120538
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1138 PM CST Sun Feb 11 2018

.UPDATE...
Issued at 1138 PM CST Sun Feb 11 2018

Updated aviation discussion.

UPDATE...
Issued at 713 PM CST Sun Feb 11 2018

Updated to issue short fuse winter weather advisory through midnight
for all of western KY/sw IN and a small portion of se IL.
Though precip amounts will be very light, even trace to light
amounts of freezing rain/sleet will cause some travel impacts with
temps below freezing...especially on bridges and overpasses.

&&

.SHORT TERM...(Tonight through Monday night)
Issued at 313 PM CST Sun Feb 11 2018

We will monitor closely the chance of precipitation this evening.
The models vary somewhat with the northwest extent of this
second light precip event, driven by the approach of a mid level
positive tilt short wave seen on water vapor over the plains.

The CMC is the farthest NW with precip this evening (more along
the Ohio River to start). All the models show precip chances
across west Kentucky. As the cold air in the low trop deepens, we
should see more of a wintry mix vs. the light freezing
rain/drizzle we saw last night into early today. Temperatures
today went nowhere, so we are starting slightly colder heading
into the next several hours. We will account for the most
northwest solution, and have at least a slight chance along a line
from Poplar Bluff Missouri to Evansville Indiana south. Highest
chance PoPs will be across west Kentucky.

For now, after coordination with neighboring WFO`s will continue
with a Special Weather Statement approach. Our PoPs are in chance
category given the element of uncertainty, thus a statement vs. an
Advisory (usually issued with higher confidence). In play will be
the potential for an upgrade to a Winter Weather Advisory should
we start to see notable travel impacts, as we did overnight in
the previous Advisory and statement areas.

The precipitation should wind down by midnight or 1 a.m. across
the KY Pennyrile region. Dry, weather for Monday through Monday
night with high pressure continuing to build into the area.

.LONG TERM...(Tuesday through Sunday)
Issued at 313 PM CST Sun Feb 11 2018

Variability continues to be an issue with the weekend regional model
blended guidance for the extended forecast period. Although low
amplitude ridging still remains in force across the WFO PAH forecast
area Monday through early Wednesday, there has been some variation
in the western extension of the low level ridge across the Gulf of
Mexico. This variability is allowing for moisture advection
northward the Lower Mississippi Valley as early as Tuesday into the
WFO PAH forecast area.

At this point, there is low confidence that enough lift and
instability will be in place late Tuesday night into Wednesday
morning, but for collaborative purposes, have kept a small chance of
precipitation in place Tuesday night. However, some of the model
guidance suggests there may even be enough elevated instability to
warrant at least an slight chance of thunderstorms as a weak warm
frontal zone develops to the south and west with time.

There does not be significant forcing as the warm frontal zone lifts
north of the WFO PAH forecast area Wednesday into Thursday, but
suspect the guidance is keying in on warm air advection showers
being isentropically lifted across the area.

The channeled vorticity and enhanced lift from an approaching
northern stream, positively tilted, shortwave on Thursday will
tighten the baroclinic zone and lift across the WFO PAH forecast
area from north to south Thursday into Friday, with the best QPF
expected Thursday night along and just ahead of the cold frontal
passage Thursday evening.  The ECMWF, GFS, and Canadian are slowly
getting closer on the timing of the frontal passage.

A light wintry mix still seems to be possible early Friday morning
and again Friday evening, but the transition zone of temperatures
versus available moisture for precipitation continues to shrink with
successive model runs.

There was more consensus with surrounding office to move
precipitation out of the WFO PAH forecast area Saturday and Saturday
night as high pressure builds in.  This may be short-lived by Sunday
and Sunday night, as the remnants of the Southwest U.S. closed low
moves across the southern Plains to the Mississippi Valley,
including the WFO PAH forecast area.

The trend the last several model runs has been to increase
temperatures at a rate of 3 degrees a day...with ten degree spikes
each day from Monday through Wednesday.  Not sure, if it will be
totally realized due to precipitation chances on Thursday, but the
GFS and other guidance is even suggesting 70+ temperatures in
southeast sections of the WFO PAH forecast area Thursday afternoon.
Not too optimistic in seeing temperatures that high this week.

&&

.AVIATION...
Issued at 1138 PM CST Sun Feb 11 2018

As a drier airmass moves in, MVFR cigs will break up from the north
and west overnight. Winds will gradually veer to a more
northeasterly direction, with sustained speeds up to 12 knots.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Winter Weather Advisory until midnight CST tonight for ILZ090-
     091-094.

MO...None.
IN...Winter Weather Advisory until midnight CST tonight for INZ081-
     082-085>088.

KY...Winter Weather Advisory until midnight CST tonight for
     KYZ001>022.

&&

$$

AVIATION...DB



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