Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 181152
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
652 AM CDT THU AUG 18 2016

.UPDATE...
Issued at 652 AM CDT Thu Aug 18 2016

As expected, the low clouds are winning out over fog except in a
very few fairly isolated locations. The SPS should handle the
situation just fine.

The AVIATION section has been updated for the 12Z 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
expected.

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

Above average confidence in the extended...mainly due to numerous of
model consistency.

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 strong long wave trough associated with it that will help
push this front through rapidly. Forecast sounding indicate very
stable and dry conditions setting 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 models
solutions. Especially with high pressure at the surface and ridging
aloft from the GFS and Canadian vs. nearly zonal flow with ECMWF.

&&

.AVIATION...
Issued at 652 AM CDT Thu Aug 18 2016

The IFR and lower conditions over much of the area will linger
well into the morning before conditions improve to MVFR levels.
All evidence points to MVFR ceilings lingering through the
afternoon and into the evening. KOWB will likely keep the MVFR
ceilings through the night as well, but the other sites will
attempt to get to VFR levels. However, clearing will likely be
short-lived as fog or low clouds are likely to reform. For now
will keep it at MVFR levels for the overnight hours, but that may
not be low enough. Will also have to watch for shower development
at KPAH near 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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