Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 170832
AFDPAH

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PADUCAH KY
332 AM CDT Wed Sep 17 2014

.SHORT TERM /Today through Friday/...
Issued at 330 AM CDT Wed Sep 17 2014

In the near term...the main issue is fog that has developed
overnight. Though it is very difficult to estimate the depth and
coverage of the fog...all of the available surface obs from southern
Illinois /except Metropolis/ indicate vsbys are below a mile as of
08z. Will issue a Dense Fog Advisory for southern IL only. While
there are a few reports of dense fog elsewhere...it should be
relatively patchy and shallow in those areas.

The fog will burn off by mid morning...followed quickly by the
return of cloud cover. The leading edge of these clouds was
already along a KPOF/KFAM line at 08z. These clouds will
overspread the remainder of se Missouri and all of southern
Illinois by 13z.

Radar indicates scattered showers and storms forming over eastern
Kansas...which is in good agreement with the models. This activity
is associated with a mid level shortwave moving southeast into the
Plains. The shower activity will develop quickly eastward into
southeast Missouri this morning along a fairly strong low level
moisture gradient. The showers will dry up as they move into drier
air over western Kentucky and southeast Illinois...but the models
disagree on how far east they will make it. Will continue with
chance pops in southeast Missouri and slight chance pops in far
west Kentucky and sw Illinois. Due to widespread cloudiness...will
forecast high temps on the cool side of the model guidance
envelope...similar to ecmwf mos.

For tonight...the models indicate precip will linger across
southeast Missouri along the low level moisture gradient as
another upper level impulse moves southeast. Elevated instability
is forecast to increase over southeast MO this evening. Capes will
be near 1000 j/kg for parcels based around 900 mb /per 00z nam/.
Will continue with mention of thunder tonight. The eastern extent
of cloudiness tonight will play a role in the low temp forecast.
Given the strong gradient of cloud cover and dew points...there
may be a large temperature range from west to east late tonight.

On Thursday...surface high pressure over the Great Lakes region
will bring a surge of drier air on northeast winds. This will
shunt the moisture gradient and associated cloudiness westward.
Expect lots of sunshine by afternoon in all areas. This will help
temps reach the 70s despite the slight cooling at 850 mb.

On Friday...upper level ridging will build across our
region...ensuring dry conditions and somewhat warmer temps.

.LONG TERM /Friday night through Tuesday/...
Issued at 330 AM CDT Wed Sep 17 2014

The extended forecast is virtually unchanged from yesterday. A ridge
of high pressure aloft Saturday will give way to increasing
northwest/cyclonic flow, as the upper flow amplifies significantly
heading into next week.

The ECMWF, GFS, and GEM have diverged a bit with the timing of this
amplification and also in the fate of T.S. Odile. The GFS and GEM
are in reasonable agreement with the storm system Saturday night and
Sunday, but the GFS is more amplified by Sunday. Neither model shows
much in the way of coherent return flow ahead of the cold front, and
the GEM, which keeps the tropical remnants over the southern Plains,
really struggles to generate QPF over our region. The GFS seems to
bring the remnants across at least southeast Missouri Saturday
night, but that does not lead to a significant QPF output.

The 00Z ECMWF is much slower with the amplification process, and
doesn`t bring the cold front through until Sunday night. It takes
the tropical remnants from southwest Missouri into Arkansas Sunday
night as well. This is a significant change from just 24 hours ago,
so will discount it at this time.

Typically when there is a consistent signal in the models for 2 to 3
days, its time to ramp up PoPs.  However in this case, will keep
them at the 40% level, since there is a reasonable chance that parts
of the region will see little, if any, rainfall.

Guidance seems to be warming up for highs on Saturday. The ECMWF MOS
has a high of 87. This forecast is a degree or so higher than
yesterday`s forecast, which is just shy of the ECMWF guidance.
Probably the biggest question for temperatures will be on Sunday,
with the potential for precipitation in the slower ECMWF solution,
and the weaker initial frontal passage of the GFS solution. This
forecast may be a bit cool Sunday. Temperatures should drop well
below normal by Monday and Tuesday of next week. It appears that the
better cold advection may occur Monday night into Tuesday, so
Tuesday will definitely be the coolest day of the extended forecast.

&&

.AVIATION...
Issued at 330 AM CDT Wed Sep 17 2014

Areas of fog will burn off by mid morning. The fog is rather
shallow and patchy at kpah as of 08z...but without the benefit of
webcams there is no way to estimate its depth at other locations.
ASOS vsbys will be near one quarter mile at kcgi and kpah at
times...but kevv and kowb will likely stay higher.

For kpah and kcgi...low and mid clouds will overspread the region
this morning...with mainly vfr cigs anticipated today and tonight.
Areas of light rain are not expected to significantly impact
vsbys.

For kevv and kowb...the clouds will be mainly of the mid to high
variety...and no rain is expected there.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
MO...NONE.
IL...DENSE FOG ADVISORY until 9 AM CDT this morning FOR ILZ075>078-
     080>094.

IN...NONE.
&&

$$

SHORT TERM...MY
LONG TERM....DRS
AVIATION...MY





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