Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 171314
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
814 AM CDT Fri Aug 17 2018

.UPDATE...
Issued at 814 AM CDT Fri Aug 17 2018

Updated aviation discussion.

&&

.SHORT TERM...(Today through Sunday night)
Issued at 400 AM CDT Fri Aug 17 2018

The approach of a mid level shortwave trof toward the PAH
forecast area was apparent this morning, providing forcing for
showers and tstms initially. As the atmosphere stabilized some
this morning, the western batch of pcpn settled into an extensive
area of light to moderate rain, with isolated lightning strikes.
Meanwhile, isolated to scattered showers and tstms continued to
form in the Evansville Tri-State region, and will probably merge
with a convective complex moving southward out of central IL early
this morning. The strength of this activity will continue to be
monitored, plus flooding potential, as it expands into northern
parts of the region. Meanwhile, the large stratiform area of rain
affecting the western and southern areas should diminish in
coverage toward sunrise. This is the best estimate for now based
on a general consensus of models, despite erratic forecasts by the
CAMs.

After a possible lull in pcpn after sunrise, as the mid level trof
axis closes in, shower and tstm activity is expected to re-fire
across the region in the heat of the afternoon. Plenty of
cloudiness is expected to limit tstm strength overall in the
afternoon, though a few storms may still become strong south of
the OH River where the best instability should be. Damaging wind
will be the main concern there.

PoPs will gradually decrease tonight as the trof axis arrives.
however, despite decreasing deep moisture, it appears the
presence of the slow-moving axis will continue to provide enough
instability for scattered showers and even some tstms to form
mainly east of the MS River during the day Sat.

After a brief period of ridging Sat night and much of Sun, a
vigorous low pressure system will approach our region late in the
short term period, ramping up PoPs again west-to-east Sun night.

.LONG TERM...(Monday through Thursday)
Issued at 400 AM CDT Fri Aug 17 2018

Long term starts out with our next storm system over Kansas, taking
shape and barreling toward the FA. It spins a warm front
northward across the area, with associated convection, during the
daytime Monday, as the Low advances into Missouri by 00Z Tuesday.
The cold front enters the forecast picture, and drives to the
Mississippi river Monday night, as the Low tracks due eastward
into Illinois. This will shift the elevated/warm sector convective
mode, to linear/frontal driven convection. The surface cold front
completes its passage across the FA Tuesday morning, as the Low
tracks up/just north of the Ohio river, across Indiana and into
Ohio by 00Z Wednesday. The upper trof digs/shifts with the storm
system, but lags by 6-12 hours as heights continue to fall thru
12Z Wednesday. The trof sharpens during the daytime Wednesday, but
the trof axis does look to be just to the east of our FA, so we
think the GFS is perhaps a little overdone (per usual) with its
overall QPF that extends behind the trof into our eastern
counties. High PW`s and continued good moisture advection ahead of
this system will make for heavy rainfall continuing as a storm
hazard. Strong storms may be possible in the warm sector,
diurnally enhanced, Monday, or along/ahead of the cold front,
mainly western portions Monday evening, into Monday night. If so,
damaging winds looks to be the associated hazard, given the
increasing depth of shear as the Low itself approaches.

The best news on the extended comes in the latter portion, as we
replace the active wet weather system and associated trof with
surface High pressure and cooler/drier northwesterlies aloft. This
occurs in response to our wedging between the developing western
CONUS ridge and the eastern CONUS trof. This continued/persistent
model signal is upping our confidence level in Highs in the lower
80s (with lower humidity), and Lows in the lower 60s (even some
upper 50s), as we move into the middle and latter portions of the
work week.

&&

.AVIATION...
Issued at 814 AM CDT Fri Aug 17 2018

VFR conditions are anticipated through the morning hours across the
region. However, as showers and tstms re-fire this afternoon, MVFR
cigs are possible by afternoon, at least intermittent ones,
associated with the activity. There is some uncertainty whether
widespread MVFR cigs will occur. If they do, they should occur in
the eastern half of the region, including KEVV/KOWB. Meanwhile,
southwesterly winds will continue up to 12 knots sustained during
the daylight hours, going light tonight with the beginnings of a
shift to the northwest late. Clearing skies in the western half of
the region will be conducive to fog formation late in the night,
with IFR vsbys possible.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

SHORT TERM...DB
LONG TERM...DH
AVIATION...DB


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