Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 210455
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1155 PM CDT Thu Jul 20 2017

.UPDATE...
Issued at 1155 PM CDT Thu Jul 20 2017

Updated aviation section for 06z TAF package.

&&

.SHORT TERM...(Tonight through Saturday night)
Issued at 241 PM CDT Thu Jul 20 2017

The main story is of course the heat. The center of a 500 mb ridge
will move east, parking itself directly over the Kentucky-Missouri
border on Friday. The 595 dm center will peak over west Kentucky
Friday evening, then a very subtle weakening trend and southward
drift will occur Saturday. This subtle trend will not be enough to
bring changes to our sensible weather Saturday. However, the
long-term discussion will detail some noticeable changes beyond
Saturday.

In the near term, heat indices early this afternoon ranged from
100 to 105 at most stations. Stations falling outside this range
were showing oddities in surface dew point readings. For example,
the dew point of 66 at kevv was 8 to 12 degrees lower than
surrounding sites. The 80-degree dew point at kpof fell on the
other extreme.

Little change in temps or dew points is expected through Saturday.
Afternoon highs should continue to be in the mid 90s, with
overnight lows in the mid 70s. This will continue to produce peak
heat index values near 105 each afternoon.

Precip chances appear very low under the 500 mb ridge, but the 12z
mesoscale models are increasingly pointing to convection in
southwest Indiana on Friday afternoon. The operational model blend
used here indicates a 20 to 30 percent pop in sw Indiana and
adjacent counties Friday afternoon. This is actually lower than the
short-range ensemble pops (sref) for that area. The forecast will go
with 20 to 30 percent pops in sw Indiana and adjacent counties.
This region will be on the periphery of the mid-level high, and a
convective outflow boundary could impinge on southern Indiana.
Any such convection and its outflow cirrus could affect heat index
values, but right now the most likely scenario is a repeat
performance of today.

Precip chances will increase north of the Ohio River Saturday
night as a cold front approaches.

.LONG TERM...(Sunday through Thursday)
Issued at 241 PM CDT Thu Jul 20 2017

This period starts out with a ridge centered over the western
U.S. and troughing over the Great Lakes region. Initially our area
is in more of a zonal flow, with a cold front expected to push
through during the Sunday/Monday time frame. This will lead to a
chance of mainly afternoon/evening convection affecting the whole
region Sunday and mainly just southern counties come Monday. One
last day of heat index readings over 100, and around 105 in some
locations, is expected on Sunday.

Drier and cooler air associated with surface high pressure over the
upper midwest is expected to push into northern counties by Monday
and through the entire area by Tuesday into Wednesday. This is
modeled well by both the GFS and Canadian deterministic models and
ensemble means. However, the 00z and 12z ECMWF runs continue to wash
out the front and thus prevent the drier, cooler air from
penetrating all the way through the region. This would essentially
keeps dewpoints above 70 and temperatures in the 90s, at least for
the southern half of the area. The 12z ECMWF also keeps rain chances
in through much of next week with waves of energy riding along the
remnant boundary. Will continue to side with the consensus and
disregard the ECMWF for now, but will need to monitor it as it has
been fairly consistent in holding up the front further north.

Given the expected north/northeast fetch of drier air, dewpoints
should lower into the 60s areawide by Tuesday and Wednesday.
Temperatures will lower to near normal with highs generally in the
upper 80s and lows back into the 60s.

Isolated convective activity can`t completely be ruled out Tues/Wed
especially across southern and western counties closer to the better
moisture and instability. However, chances are too small to mention
this far out. Rising upper level heights by Thursday should
translate in a slight uptick in temperatures. Mentioned slight
chance PoPs for this period given a shortwave moving by to our
north, and this may lead to some activity making it into our
region.

&&

.AVIATION...
Issued at 1155 PM CDT Thu Jul 20 2017

MVFR fog is possible between 09z-13z, otherwise VFR conditions
through the TAF period. FEW-SCT050 cu expected after 15z. Southwest
winds around 3 kts will increase to around 6 kts after 13z.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 7 PM CDT Sunday for ILZ075>078-080>094.

MO...Heat Advisory until 7 PM CDT Sunday for MOZ076-086-087-100-
     107>112-114.

IN...Heat Advisory until 7 PM CDT Sunday for INZ081-082-085>088.

KY...Heat Advisory until 7 PM CDT Sunday for KYZ001>022.

&&

$$

SHORT TERM...MY
LONG TERM...SP
AVIATION...RST


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