Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 031739 AAA

Area Forecast Discussion...UPDATED
National Weather Service Paducah KY
1139 AM CST Sat Dec 3 2016

Issued at 1139 AM CST Sat Dec 3 2016

Updated the aviation discussion for the 18z TAF issuance.


.SHORT TERM...(Today through Monday night)
Issued at 327 AM CST Sat Dec 3 2016

Considerable cloud cover today given satellite trends. High
pressure should keep most of the area dry. Some light rains
could move into SEMO, SW KY by dark as Isentropic lift seen on
295-300k surfaces increases coincident with increasing moisture.

Tonight, rain chances will increase, though areal coverage may be
non uniform. A mid level trof over the Plains 06-12z Sunday will
support precip to our west, while along and east of an inverted
surface trof we will see rains move NE into the area then shift
toward the TN valley tonight through Sunday morning. As the Plains
trof moves east and becomes positioned over the Great Lakes and
Ohio Valley, drier air working in from the west will end precip
chances from west to east Sunday.

Dry weather is forecast Sunday night as high pressure maintains.
Next system of interest will be an H5 low over the Rio Grande
around 12z Monday. The low is forecast to eject NE and be over NE
TX by 00z Tuesday, then accelerate and open up Monday night,
ending up over West TN by 12z Tuesday. The NAM looks way too
aggressive and overdone spreading rains over the area Monday
afternoon. This is an outlier trend, and not supported by the
slower GFS, CMC and EC. We will give it about 20 percent weight,
and an even 80 percent with the other 3 for timing Monday
afternoon and evening. Eventually PoPs will reach categorical
Monday night as ample moisture and lift generate showers and
possible isolated thunder/lightning.

Will tend to the cool side of MOS, toward the NAM today given
clouds and the chilly start this morning. After that we used a
blend of MOS and base model blend output.

.LONG TERM...(Tuesday through Friday)
Issued at 327 AM CST Sat Dec 3 2016

At the beginning of the long term period, a compact negatively tiled
shortwave will be making its way across the area. This system will
be lifting northeast and out the area rather quickly though during
the morning/early afternoon. Most of the precipitation that will
likely be ongoing during the morning hours, will be occurring over
our eastern sections; the rain will be departing the SEMO counties
during the morning hours.

After that system moves out...we will be sitting in southwest flow
aloft waiting for the next system to impact the area. Models
continue to have issues in timing and strength of this next system.
Both models start bringing colder air into the region with a sfc
high Tuesday night into Wednesday. The ECMWF continues to be slower
with bringing a large scale trough across the country`s mid section
on Wednesday and indicates any precipitation will likely hold off
until after 00Z Thursday. At that time, a sfc low develops to our
southwest which races northeast Wednesday night and ends up over our
southeastern counties by 12Z Thursday. Because of this, the cold air
infiltration halts for a while. But cold air eventually gets pulled
into the area, but does so behind the precipitation, so most of the
precipitation will likely remain all liquid but a brief changeover
to snow is entirely possible.

The GFS is consistently faster, colder and indicates much less QPF.
According to the GFS, the cold air is already making its way into
the region during the day on Wednesday and as the upper wave reaches
the area. Therefore, any of the low QPF that is generated, could be
in the form of flurries or light snow showers.

Given the severe lacking of model consistency, am not inclined to go
hook line and sinker on any one model or model run. Is light snow a
possibility with this system - yes. How much and when remains
questionable at this juncture. Will run with a compromise as far as
timing for now, with slight chances in the west for rain in the west
prior to 00Z Thursday. On Wednesday night, will opt for a rain/snow
chance north in the evening. Then, for the overnight hours, decided
on a rain/snow chance south, light snow showers north. Keep it
simple for now. Could have some lingering flurries/light snow
showers early Thursday morning.

Despite the timing issues, models are agreeing that some pretty cold
air will be spilling into the region late Wednesday night into
Thursday as arctic high pressure builds in. In fact, lows will be in
the teens Thursday night. Expect the cold weather to stick around a
while but some locations could rebound to near 40 degrees for highs
by Saturday.


Issued at 1139 AM CST Sat Dec 3 2016

VFR conditions will prevail through the afternoon. Lowering cigs
and light rain will enter from the south and spread NE overnight.
Expect MVFR cigs/vsbys to develop at KCGI/KPAH and areas further
south and west. For Sun AM, expect MVFR cigs/vsbys to work NE
toward KOWB, with IFR cigs further south at times. East winds
generally AOB 10 kts tonight, becoming ESE Sunday.




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