Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 181801

Area Forecast Discussion
National Weather Service Paducah KY
101 PM CDT THU AUG 18 2016

Issued at 101 PM CDT Thu Aug 18 2016

The AVIATION section has been updated for the 18Z TAF issuance.


.SHORT TERM...(Today through Saturday night)
Issued at 322 AM CDT Thu Aug 18 2016

It appears that LIFR ceilings are winning out over fog over much
of the region early this morning. KFWC and KMVN along I-64 are
bouncing under a mile, and this area is on the fringe of the
clouds, so will monitor this area for a potential Dense Fog
Advisory through sunrise. May just go the SPS route, given the
uncertainties with ceilings.

The 00Z models are in decent agreement in keeping a weak shear
zone at 700mb over our region. It shows up real good in the VWP
data from area radars with northeast winds at KPAH and southwest
winds at KHOP and KOHX. This will keep things stirred up along our
southern border.

Most 00Z guidance emphasizes the late night/early morning
timeframe both today and again late tonight into Friday for decent
coverage of showers and possibly a few thunderstorms. Will focus
PoPs in the south through Friday morning, with the best chances
in the morning hours. The shear zone gets wiped out by Friday
afternoon, as a more substantial mid/upper-level trough approaches
the area from the west. This will allow for a chance of convection
throughout the area Friday afternoon and night.

The 00Z guidance is in pretty good agreement in developing fairly
widespread convection Saturday afternoon, as a rather vigorous
(for August) mid/upper-level trough emerges from the Plains by the
end of the day Saturday. The associated cold front will enter
southeast Missouri and southern Illinois in the late afternoon.
With the forcing, presence of a boundary, and strengthening deep
layer wind fields, a few severe storms will be possible along and
ahead of the cold front Saturday afternoon. Instability will be
meager at best, but cannot argue with SPC`s Marginal Risk at this
time. Of course, locally heavy rainfall and lightning will be more
prevalent threats with thunderstorms on Saturday.

Did not stray much from guidance on temperatures through the
period. However, did go a bit above the consensus on lows Friday
night with more persistent south winds and plenty of cloud cover

.LONG TERM...(Sunday through Wednesday)
Issued at 322 AM CDT Thu Aug 18 2016

Above average confidence in the extended...mainly due to model

A fast moving cold front will move through Saturday night, resulting
in a high chance of thunderstorms with strong confidence. By
Saturday night however, the severe threats decrease significantly
after sunset. The surface based Li`s drop from negative 4 or 5
depending on which model you choose. And the Surface based CAPE
falls from 2k j/kg/2 to less than 100 between 00z and 6z; again all
models indicate this trend but some are slower than others to
diminish the instability.

An upper level long wave trough will be poised to move through the
area this weekend. The front will be exiting the area at the
beginning of the extended with much cooler and drier air in its wake.
Unlike the previous front that lay stalled over the area...this
front has a strong long wave trough associated with it that will
help push this front through rapidly. Forecast soundings indicate
very stable and dry conditions settling in for Sunday and after. All
severe potential will be out of the are by the start of the extended
with a very unseasonable/comfortable week ahead of us.
Otherwise the next frontal system set to move through the area will
be next weekend or the last weekend of August. Yes, after a record
setting rainfall for August, we still have two more good chances of
rain before September; one this weekend and another next weekend.
The ECMWF is hinting at a weak front possible before next weekend
around Thursday but has very little support from other model
solutions, especially with high pressure at the surface and ridging
aloft from the GFS and Canadian vs. nearly zonal flow with ECMWF.


Issued at 101 PM CDT Thu Aug 18 2016

All evidence points to MVFR ceilings most terminals lingering
through the afternoon and into the evening, though there may be some
periods of VFR, especially in parts of southern IL. VFR cigs are
possible by sunset. However, clearing will likely be short-lived as
fog or low clouds are likely to reform overnight. At this time, it
appears there will be enough wind just off the surface to diminish
the likelihood of dense fog. Instead, IFR to low MVFR cigs are
likely. Conditions should begin to improve by mid morning Thursday,
but shower activity is expected to begin to move in from the south.


.PAH Watches/Warnings/Advisories...


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