Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 171957

Area Forecast Discussion
National Weather Service Paducah KY
257 PM CDT Sat Mar 17 2018

.SHORT TERM...(Tonight through Sunday)
Issued at 257 PM CDT Sat Mar 17 2018

The cold front is making quick progress southward through the
region, and the potential for convection is limited to Muhlenberg,
Hopkins, Christian and Todd counties. That potential is fleeting
as the front will clear those areas by 22Z. Satellite imagery
shows considerable bubbling of cu in those areas just ahead of the
front, but no deep convection has developed. We will continue to
monitor, but the threat of thunder and severe is dwindling quickly.

500mb heights will climb in the wake of this storm system tonight,
as weak surface high pressure settles overhead. Gusty northwest
winds will subside this evening, and light winds are expected
overnight. The large area of lower ceilings has been progressing
eastward through southern Illinois and is about to enter
southwest Indiana, but the southern extent has been held off by
strong mixing over southeast Missouri. The consensus of guidance
will eventually spread the low cloud over the entire region later
tonight, and that should help hold temperatures up a bit, but it
will still be quite cool compared to the 70s some of us have
experienced this afternoon. Temperatures should not get down to
freezing even in the far north or northwest.

High pressure at the surface and aloft will dominate the region
Sunday. The low clouds may be slow to erode, and deepening high
clouds will be spreading eastward over the area through the day,
so sunshine will be limited. Went on the cool side of guidance
where possible, but not as low as the NAM-based guidance.

As our next storm system emerges from the Rockies, warm advection
showers may reach our far southwestern counties just before
sunset Sunday. No sign of instability to support thunder, so just
a few showers will be possible generally after 4 PM.

.LONG TERM...(Sunday Night through Saturday)
Issued at 257 PM CDT Sat Mar 17 2018

For the latter part of the short term and extended portion of this
forecast package, it appears that the best potential for strong to
potential storms will be late morning into late afternoon on Monday,
then again next Saturday evening.

There is the potential for some storms approaching severe limits in
southeast Missouri between 06z-09z (1am-4am CDT) this Sunday night,
but the potential is quite conditional.

The first precipitation event is initiated from a shortwave moving
rapidly from the Four Corners area of the desert Southwest midday
sunday, becoming a vertically-stacked intense low over northeast
Oklahoma by 7 am CDT Monday. Showers will already be breaking out
across the Quad State region Sunday night, as broad scale lift,
moisture and instability will be readily present across the area.
Cannot completely rule out as strong storm in the 06z-12z Monday
time frame, but looking at the CMCnh (Canadian) and 12km NAM 12z
Saturday guidance, it appears that there is too much potential for
contaminated updrafts for any organized convection overnight.

However, the probability for strong to severe storms does increase
as the upper low begins to move through south central Missouri
between 12z-18z Monday. With drier air being fed into the southern
quadrant of the low aloft, anticipate some fairly rapid overturning
of parcels across southeast Missouri and the Purchase area of West
Kentucky. Between 18z-21z, the surface-based potential for severe
weather shifts toward the southern Purchase/Pennyrile region of west
Kentucky, tied to the proximity of surface low/frontal boundaries.
The regionally blended model initialization probabilities of
thunderstorms plaster elevated thunderstorms much further north
across the WFO PAH forecast area. Given some forecast uncertainty on
the northern limit of the thunderstorms activity, will leave a
conditional mention of thunderstorms over the eastern part of the
forecast area (north of the surface low) through the rest of Monday

The main challenge will be how far the instability works northward
into the WFO PAH forecast area. The CMCnh (Canadian) is furthest
north with the surface low in western Kentucky, the ECMWF (European)
the furthest south, with the NAM-WRF splitting the difference. This
will have a definite impact on any severe potential in west Kentucky
Monday afternoon.

The 00z Canadian model guidance attempted to introduce some light
late Tuesday into Wednesday on the western edge of an upper trough,
but the 12z Saturday model run, along with the 12z ECMWF have
dropped any potential for precipitation.

Relatively dry weather, subject to ridging aloft will dominate from
Tuesday through late Thursday or Friday. Warm advection showers will
break out as a strong moisture/wind gradient builds between an Ohio
Valley ridge and an eastern Colorado low. Given the colder
temperatures aloft and at the surface, some of the precipitation may
be a light mix late Thursday night. Suspect there will be some
timing issues with the second system late next week, but it looks
very likely for scattered warm sector, isentropically lifted,
showers will dominate from Friday onward. The next chance for
thunderstorms will likely occur next Saturday night.


Issued at 1240 PM CDT Sat Mar 17 2018

A cold front will push through the TAF sites by 20Z and the entire
area by 22Z. Northwest winds will gust 20-25kts behind it through
sunset, and west winds will gust ahead of it. A few thunderstorms
may develop just to the south or southeast of KOWB early this
afternoon, but not close enough to impact KOWB.

Broken MVFR ceilings will accompany the cold front at KEVV and
KOWB, but more scattered conditions are expected farther
southwest. A large area of MVFR and even IFR ceilings will
eventually spread east across KEVV and KOWB later this afternoon
and they will likely linger through the end of the period. Most
recent guidance drags the MVFR ceilings south with time such that
they may impact KCGI and KPAH overnight into Sunday morning.




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