Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 111156
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
556 AM CST Sun Dec 11 2016

.UPDATE...
Issued at 556 AM CST Sun Dec 11 2016

Solid overcast skies and increasing south winds have held
temperatures up some 20-25 degrees warmer than this time
yesterday. What a difference a day makes.

The AVIATION section has been updated for the 12Z TAF issuance.

&&

.SHORT TERM...(Today through Tuesday night)
Issued at 303 AM CST Sun Dec 11 2016

A solid layer of 5-6kft clouds and south winds 5 to 10 mph are
holding temperatures up early this morning. As of 09Z, current
readings are within a degree or two of yesterday`s high
temperatures. See no reason why we would drop much if at all
through sunrise.

The upper-level storm system that will eventually push the cold
front through our region tonight is currently pushing east into
North Dakota, and is forecast to reach Michigan by 12Z Monday. The
00Z models have pretty good agreement on this as well as the
timing of the front through the region from 03Z through 12Z.

The general trend in the 00Z guidance, especially the CAMs, is to
delay the onset of significant precipitation across the region
until around 21Z and then ramp it up heading into the evening. It
looks like the primary wet period will be from 21Z through 06Z,
with a rapid drying trend from the northwest overnight. The 00Z
models have no QPF after 12Z Monday, but the models have been
waffling back and forth with this timing over the last few days.
Decided to continue with a slight chance into Monday morning in
the far southeast.

Another issue is where the back edge of the precipitation will
be. The bulk of the 00Z guidance emphasizes development from the
Missouri Boot-heel northeast along the Ohio toward KEVV this
afternoon, and then an eastward progression through the area
tonight. The bottom line is that our western and northwestern
border areas may not see much rainfall with this event. We still
have the same general gradient in QPF, ranging from around a tenth
of an inch in the northwest to two thirds in southern Todd county.
The NAM seems a bit aggressive with its warm/moist surge around
850mb, so will ignore its negative Showalter Indices and keep
thunder out of the forecast. No other models are generating much
in the way of elevated instability.

A weak mid-level disturbance is forecast to move eastward from the
southern Plains to the Mississippi Valley Monday night. With the
old cold front draped east to west somewhere across Mississippi
and Alabama, there is some potential of a few showers or sprinkles
with this disturbance in the southern half of our region. Most of
the 00Z guidance is dry late Monday night, so will keep the
forecast dry and keep an eye it. Temperatures will be near
freezing, so even a little bit of precipitation could be
significant.

The next chunk of Canadian surface high pressure will surge
southeast through the region late Tuesday and Tuesday night.
Northern portions of the area may see temperatures falling in the
afternoon. The forecast winds may not be great enough based on the
rather impressive gradient Tuesday night.

Tried to go closer to the warm side of statistical guidance for
high temperatures today and Monday, but otherwise the consensus of
all available guidance looked reasonable.

.LONG TERM...(Wednesday through Saturday)
Issued at 303 AM CST Sun Dec 11 2016

High confidence in the extended through most of the week. Confidence
is increasing for the weekend but still a great deal of discrepancy
in the models for that time frame.

Models are trending warmer with this end of week system...however
there remains a great deal of discontinuity especially with
temperature profiles. The ECMWF MOS has 46 for Fridays high while
the GFS has 34 at Paducah. This creates a great deal of uncertainty
in precip type as one would imagine. However the blend is warming
from previous runs and if this trend continues it will likely be
mostly liquid vs frozen. Current thinking is a mix for now with much
less impact than previous runs predicted. We will essentially by
under the influence of cold high pressure until late Friday when a
warm front lifts through the region...changing any frozen
precipitation to mainly liquid. Things may get a little interesting
after Saturday as cold front moves into the region...this could
change precipitation back to frozen before ending. Otherwise very
cold Wednesday and Thursday with temperatures struggling to reach
freezing...and most everyone staying below freezing at least until
Friday. For now the main impact would be the longevity of below
freezing temperatures. In summary this end of week system will need
to be monitored closely as the models are in a great deal of flux
with surface temperatures.

&&

.AVIATION...
Issued at 556 AM CST Sun Dec 11 2016

South winds will gust this morning and into the afternoon before
diminishing a bit ahead of the cold front. In general,
deteriorating conditions are expected from late this afternoon
through the cold frontal passage late tonight. The worst
conditions, possibly as low as LIFR, will occur this evening in
the west and into the overnight hours in the east, as the cold
front begins to push through the region.

All sites should see the frontal wind shift. There is some debate
about how strong winds will be this evening just ahead of the
front. Tried to play the middle ground, but gusts to 20kts or more
are not out of the question into the evening. The cold front, in
addition to the wind shift to the northwest, will bring an end to
the rains and should bump ceilings up into MVFR territory at all
sites by the end of the period.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

UPDATE...DRS
SHORT TERM...DRS
LONG TERM...KH
AVIATION...DRS



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