Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 181732
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1232 PM CDT Sun Jun 18 2017

.UPDATE...
Issued at 1232 PM CDT Sun Jun 18 2017

Updated aviation section for 18z TAF package.


UPDATE Issued at 1209 PM CDT Sun Jun 18 2017

Very small MCV (aka "bookend mesocyclone", in this case) developed
over Alexander Co. IL and evolved E-SE through the KPAH area to
just northeast of KHPX at 17z. The MCV and associated bowing
structure move into weakly to slightly moderate CAPE/Shear/lapse
rates to support continued forward propagation, but lacked
sufficient shear to support robust updrafts after it moved from
the Land Between the Lakes into a previously convectively
contaminated area over the Southern Pennyrile.

Some regeneration will likely occur over Southeast Missouri
Foothills later this afternoon with frontal zone lift. The 16z
LAPS data show some 1700-3200 J/kg2 within surface theta-e
convergence zone. KPAH VAD wind profile at 17z shows the waning
influence of the post-convective wake high. The wind profile is
showing veering at low levels to 5kft msl. There is still some
implied warming at 6-9kft msl, but slight backing of winds
9-15kft msl 9kft as leading edge of midlevel trough axis moves
into the area. The profile is not real conducive for robust
convection, but some modification will occur this afternoon as the
surface front moves into the area. The ESRL HRRR/RAP/etc...still
show some regeneration of isolated to scattered organized
convection, especially after 3 pm. The location of the SPC slight
risk area seem reasonable for the remainder of this afternoon.

UPDATE Issued at 651 AM CDT Sun Jun 18 2017

The most recent HRRR output takes the band of storms from Carter
County through Jackson County east southeast this morning, and has
the entire area dry by early afternoon. The latest radar trends
certainly support this idea, but not sure if that will be the
end of the precipitation or not.

The AVIATION section has been updated for the 12Z TAF issuance.

&&

.SHORT TERM...(Today through Tuesday night)
Issued at 253 AM CDT Sun Jun 18 2017

With the MCS entering the area and a Watch in effect will attempt
to be brief.

There appears to be plenty of instability to keep the MCS going
across much of the area through daybreak, but not sure if the wind
fields will be sufficient to keep the winds near severe levels.
We have had a rash of 40-45kt observations just upstream, and
hopefully it will stay in that range. Most of the available
guidance indicates that the system should be weakening as we head
toward daybreak, and the leading line convection certainly looks
strongest from northwest Jefferson county northward, while the
rest of the line looks rather unorganized. As for the watch we
decided to err on the side of caution. It will likely be done well
before 9 AM.

The 00Z models are quite muddled with the surface pattern later
today. The outflow from this system should push through the entire
area regardless of the strength of the convection, and the cold
front is not very well defined as it moves through our region.
The convective debris will make it hard to destabilize today, and
with the front not being very sharp/convergent, development may
not be as widespread as previously thought, and it may take longer
into the afternoon for it to develop. Not sure how much convection
we will see and therefore severe storms seem like a long shot at
this point.

It still looks like it may take most of tonight to get the front
and the last of the convection out of the area, but the cooler
weather is still on track for Monday. Unfortunately, it will warm
up above normal again on Tuesday.

.LONG TERM...(Wednesday through Saturday)
Issued at 253 AM CDT Sun Jun 18 2017

We will have weak high pressure over the area on Wednesday with dry
but warm conditions. It will not feel as humid on Wednesday either
with dew points progged to be in the lower 60s This high moves east
during the day on Wednesday and into Wednesday night.

We continue to watch a system that will be coming onshore in the
Gulf. Of course models differ on the track of this system but both
the Canadian and ECMWF bring moisture northward into our area
Thursday into Friday. This will mean the humid conditions will be
returning along with the chances for rain. The GFS shunts the system
eastward into the Gulf Coast states and keeps the moisture to our
southeast. If the Canadian and ECMWF are correct and that Gulf
system or remnants thereof come right up the Mississippi River, we
could see precipitation as early as Thursday night. These model
differences affect the forecast for Friday as well. However, the GFS
does indicate that deeper moisture will infiltrate the eastern parts
of the forecast area by Friday. Therefore, we will continue
advertising the best chances in the eastern half on Friday given the
path of the aforementioned system.

However, by Friday night into Saturday, we will be dealing with an
incoming frontal boundary from the north. Timing is fairly good
between models and good chances for convection will arrive Friday
night and last at least through Saturday night. Models have been
consistent in drying things out Sunday morning into the afternoon.


We will see high temperatures a few degrees either side of 90 for
Wednesday through Friday, with slightly lower temperatures on
Saturday given clouds/precipitation and lower readings on Sunday
behind the front.

&&

.AVIATION...
Issued at 1232 PM CDT Sun Jun 18 2017

VFR conditions will remain predominant this afternoon and a few
shra/tsra will linger/redevelop through 00z with passage of a cold
front. Coverage is expected to be widely scattered at this point,
with brief MVFR conditions possible with any precip that goes
over TAF sites. Behind the front, VFR conditions expected except
for some MVFR fog possible at all sites between 06z and 13z. Winds
will be from the west to northwest around 5 kts, becoming light
overnight.


&&

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

$$

SHORT TERM...DRS
LONG TERM...CW
AVIATION...RST



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