Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 190804
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
304 AM CDT Sun Mar 19 2017

.SHORT TERM...(Today through Tuesday night)
Issued at 239 AM CDT Sun Mar 19 2017

We begin the short term with surface High pressure ridging across
the lower Ohio river valley. Satellite still shows some cyclone
related lower clouds just to our north/east, east of the ridge,
and then some warm advection mid decks, just to our west, west of
the ridge. The models shift the surface High to the east Today,
and Tonight, as we return southerlies to the lower trop flow in a
developing warm sector. This allows the lower trop column to warm
and moisten, sufficiently so to destabilize and introduce a chance
of thunder by early Monday morning, as a zonal almost northwest
flow action aloft shoots some energy over the frontal boundary
that sets up to our north/west.

Monday, we`ll see this activity on the increase, with the
boundary sagging into the Ohio river vicinity and acting as a
focus for showers/thunderstorms. Best forcing/winds aloft shoot
the boundary east-southeasward, on across the Ohio river Monday
night, effectively laying it out along our southern FA border by
Tuesday morning. Sufficient elevated instability, and even MU
Capes in the 0-1KM layer, support continued thunder mention
throughout this time period, with rain/lightning primary
associated hazards in SPC outlooked general thunder.

For Tuesday, additional forcing aloft is added to the mix, and
with the boundary hung up along our southern border, we see an SPC
issued Day 3 Marginal risk across our south/southeastern most
counties, where the forcing best intersects the boundary and axis
of instability/moisture. Damaging winds would be the primary
severe threat/hazard, with rain/lightning continued associated
hazards. The energy, and boundary, push on out Tuesday night, so
we should then see the thunder diminish, and eventually Pops, from
north(west) to south(east) as the night wears on and some
cooler/drier air works in from a Canadian/Polar surface High that
drops down for the mid week.

.LONG TERM...(Wednesday through Saturday)
Issued at 239 AM CDT Sun Mar 19 2017

Confidence has improved a bit for the extended but still think the
longevity of pops is overdone.

We start off the extended with a surface high pressure system being
the dominant weather feature. This should mitigate any chances
for rain from overrunning the front stalled just south of the
area. A northwest flow aloft will persist until Thursday night as
upper level ridging starts to move east into the region. This will
combine with a warm front at the surface that lifts through the lower
Ohio Valley. The warm front will bring a chance of rain to the
region mainly Friday into Saturday. This system will have low
level moisture but it will also have a strong cap with very little
moisture above the cap. Instability index values are marginal at
best with LI`s staying positive and CAPEs never reaching 500
j/kg2. K index values get well into the 20s but again there is
very little moisture aloft with this system. The warm front
however will bring above normal temps to the region then return to
near normal with the cold front`s passage Saturday.

&&

.AVIATION...
Issued at 239 AM CDT Sun Mar 19 2017

VFR conditions will largely prevail through the period due to
surface High pressure remaining in the general vicinity. The
eastward shift of the High with time will allow winds to veer
toward the south, but they should remain under 10 kts. Gridded
time/height cross sections suggest some warm air advection mid
decks initiate later today, with moisture saturating downward
in the atmospheric column, toward MVFR levels tonight.

&&

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

&&

$$



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