Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 200153

Area Forecast Discussion
National Weather Service Paducah KY
853 PM CDT Thu Oct 19 2017

Issued at 853 PM CDT Thu Oct 19 2017

Winds have already become calm over much of the region, and
guidance indicates that calm winds will prevail through the night.
As a result, lowered low temperatures a few degrees, but not all
the way down to forecast dewpoints in the middle 40s. Will
continue to evaluate for further downward adjustments.

UPDATE Issued at 642 PM CDT Thu Oct 19 2017

Updated aviation discussion for 00Z TAFs.



Only a few cirrus moving our way ahead of the next system with the
upper level ride centering over our area around 06z tonight. The
ridge moves east as the trough entering the western U.S. digs and
moves east.

Increased temperatures slightly tomorrow from the blend as
southwest flow increases at all levels.

.LONG TERM...(Saturday THROUGH Thursday)

The main trough moves to the lee of the Rockies by Saturday
afternoon which will aid in thunderstorm development over the
southern Plains. Locally we will stay dry through Saturday but
both winds and clouds will increase during the day. Low level
moisture will increase as well with dew points reaching into the
upper 50s by late afternoon and into the lower 60s Sunday morning.
Adjusted the blend to CONSall for the winds and wind gusts on
Saturday per collaboration.

Models have come into better agreement for the weekend weather but
subtle differences are seen. All models develop an upper level low
to our south by 18z Monday. The ECMWF has it near the Bootheel
while the GFS/ensembles have it over Mississippi. The GFS holds on
to the upper level low and moves it into Georgia by Tuesday while
the other models quickly open it up and lift it east.

As this happens another significant short wave moves southeast out
of Canada and continues to dig the main trough over our area
during the first part of the week. All models move the main trough
over the Appalachians by mid day Wednesday.

At the surface, the front should move through the area during the
day on Sunday with the NAM being faster than the other models.
The ECMWF is a bit stronger with the upper trough and thus slower
with the eastward movement and holds the front over our eastern
sections until early Monday.

Locally heavy rain is possible. Ahead of the main trough, an
atmospheric river develops over the Plains and moves over our area
by Saturday Night. This aids in bringing precipitable water
values of 1.5 to 2 inches over the area on Sunday. This is well
above the 75th percentile for this time of year.

Instability is meager, but it is there and scattered thunderstorms
are possible Saturday night through Sunday evening. The chances
for any severe are low but not zero. Will have to wait until we
get closer and things become better defined.

Frost is possible Thursday morning. GEFS data has several members
going down to freezing Thursday and Friday mornings. Grids are
now reflecting mid to upper 30s. So it will depend upon clouds and
wind if frost is to develop.


Issued at 642 PM CDT Thu Oct 19 2017

VFR conditions will continue throughout the 24 hour TAF period as a
ridge in the flow aloft builds. Meanwhile, surface high pressure
will remain over the Appalachians, providing southerly winds 5 to 10
knots during the day and near calm conditions at night. Expect an
increase in high clouds through the period, especially Friday.




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