Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 150909

Area Forecast Discussion
National Weather Service Paducah KY
309 AM CST Wed Nov 15 2017

.SHORT TERM...(Today through Thursday night)
Issued at 306 AM CST Wed Nov 15 2017

08Z surface analysis showed a frontal boundary stretching from
southwest Ontario Canada through eastern MN/western WI, central IA
into the TX panhandle. This front will slide east today and provide
the entire area with some rain. The main item of concern today will
be tracking the scattered to numerous showers that will traverse
the area through the day and figure out the best timing of the
highest POPs. Already have showers impacting parts of the area
and this will only fill in with time from west to east. Basically
showed higher POPs increasing from west to east across the area
today. Chances for thunder appear limited at this time, but would
not be surprised to see a few lightning strikes though.

Most of the short term models start to end the precipitation in our
western sections as early as 18Z, as the actual front starts
moving into the CWA and begins scouring things out. Therefore,
will show the rain departing the area from west to east through
the afternoon hours. In fact, the entire area may be rain free by
22Z or 23Z. This will leave the evening hours completely dry.
Rainfall amounts should range between a quarter to half inch,
maybe some locally higher amounts and some of the activity out
there now does show some heavier prospects.

Low level cloudiness may linger into the evening hours especially
over the eastern parts of the area but we are looking for mainly
clear skies to occur later on this evening or overnight as surface
high pressure builds into the region.

High pressure will dominate the forecast for Thursday with a good
deal of sunshine. However, some cooler air will arrive behind the
cold front. Therefore, highs on Thursday will only be in the upper
40s to lower 50s. This sfc high will start moving east of the area
on Thursday night and moisture will begin increasing to our west.
This moisture will start impacting parts of southeast MO after
midnight Thursday night. It should mainly be just an increase in
cloudiness, but some sprinkles would certainly be possible.

.LONG TERM...(Friday through Tuesday)
Issued at 306 AM CST Wed Nov 15 2017

Confidence in the long term has improved to higher than average
given the convergence of model solutions over the past 24 hours.
Forecast confidence remains high into early next week as well.

Shortwave energy progged to enter the Pacific Northwest Thursday
night is forecast to move swiftly east across the Plains into the
Mississippi Valley Friday night and Saturday. At the surface, low
pressure is forecast to develop in the lee of the Rockies on Friday
then rapidly move northeast into the Great Lakes region on Saturday.
A cold front accompanying this low should pass through the forecast
area on Saturday. As this occurs, the potential for showers and even
some thunderstorms will exist until the front makes passage.

Fortunately, models have come into much better agreement on timing
of frontal passage, with the current GFS no more than 6 hours faster
than the ECMWF and CMC. The forecast still utilizes an overall model
blend--albeit weighted in the direction of the slower ECMWF/CMC. The
end result is a small chance for warm advection showers Friday into
Friday evening, with numerous showers and some thunderstorms
expected late Friday night into Saturday.

With such a dynamic system, it is difficult to completely rule out
the potential for severe storms. After all, deep-layer shear on the
order of 60-70 knots is forecast late Friday night and Saturday
morning immediately ahead of the front with preliminary low level
helicity values of 200-400 m2/s2. However, instability remains a key
limiting factor given the persistent signal in forecast soundings to
maintain a layer of warm air aloft even as the front presses into
the region. Models also continue to show a westerly component to the
low level flow as the front approaches with a positive tilt to the
upper level shortwave. Considering these variables and the limited
amount of instability, the potential for severe weather does not
appear to be as favorable as what it did a couple days ago. Will
maintain a close watch in the coming days though, especially given
the differences in frontal timing.

Once the system shifts east of the area, a return to dry and cooler
weather is forecast late in the weekend into early next week. A slow
warming trend back to near seasonable temperatures is expected by
Tuesday as flow turns southerly ahead of the next cold front. Models
indicate this front should pass through dry sometime Tuesday or
Tuesday night. Generally used a model blend of temperatures through
the period, with a non-diurnal temperature trend emphasized Friday
night and Saturday as the cold front makes passage.


Issued at 306 AM CST Wed Nov 15 2017

Not much change to the 00Z thinking. Showers will move across the
entire area from early this morning through the day Wednesday.
Ceilings will deteriorate with time and may reach IFR levels for a
time, especially in the east after noon. Still think that
visibilities will hold at VFR levels unless a heavier shower
impacts a terminal. Some isolated TS will be possible, but
expected coverage is too low to mention at this time. Conditions
should improve rapidly with the weak cold frontal passage in the
late afternoon or early evening. Winds will pick up from the south
after sunrise and some gustiness cannot be ruled out as they
gradually veer to west southwest just ahead of the cold front.




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