Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 290417
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1017 PM CST Mon Nov 28 2016

.UPDATE...
Issued at 1016 PM CST Mon Nov 28 2016

Post convective 30-40 knots southwest flow from 2-5kft agl showing
up in KPAH VAD wind profile. This continues to advect moisture
along the gradient of a low level ridge axis. This has generated a
band of stratus streatching along the Southeast Missouri Foothills
into Southwest Illinois.

The model suite is finally picking up on this cloud cover and the
forecast has been updated to reflect this change. The GOES-E 4km cloud
thickness, VFR to LIFR probability images are depicting this area
well. Anticipate this area will remain in place overnight,
gradually lifting by 14z Tuesday.

UPDATE Issued at 557 PM CST Mon Nov 28 2016

Allowing the remaining wind advisory for West Kentucky to expire as
scheduled at 6 pm CST.  The convective line and associated sustained
wind/wind gust potential will have moved east of the WFO PAH
forecast area by 6 pm CST.

A wake high building northeast across the area within an hour after
the passage of the convective line will keep south-southeast winds
in the 20 to 30 mph range, with a complimentary increase on the
western side of the high over Southeast Missouri. Adjusted winds
within the last 45 minutes to account for the increase in winds.
They should remain below wind advisory criteria.

The AVIATION section has been updated for the 00Z TAF issuance.

&&

.SHORT TERM...(Tonight through Wednesday night)
Issued at 235 PM CST Mon Nov 28 2016

Large area of moderate rains producing storm totals thus far on
the order of 2 to 2.5 inches over southeast Missouri and far
southwest Illinois will be coming to an end late in the day.
Amounts have been less the farther east one heads, but will
continue to rise through the early evening before all ends over
the Pennyrile of western KY by around 8 or 9 PM.

Will be fairly rapid drying behind this system overnight.
Temperatures will actually warm nicely on Tuesday with a return
to some periods of sunshine and southerly breezes around 10 mph.

Forecast confidence decreases Tue night through as deterministic
models diverge on the track of a southern stream system across the
southeastern United States. The ECMWF seems by far to be the
farthest north and west, with additional light rain tracking well
north into wrn KY all the way up to the Ohio River. GFS/Canadian
agree on farther south/east track and keep most of the region
rainfree. Out of respect for the EC...will bring some chancy POPs
back into western KY Tue night, but main message is no real
impact expected from this one.

Cooler and drier air will filter in behind the system on Wed/Wed
night as westerly winds gust over 20 MPH in many locations. Temps
will be back down into the 30s by late Wednesday night.

.LONG TERM...(Thursday through Monday)
Issued at 245 PM CST Mon Nov 28 2016

Decent confidence in the first part of the long term period however,
we are still having model discrepancies over the weekend.

On Thursday, our region will be on the south side of a deep upper
level low centered over southeastern Canada and into the Great
Lakes. This low will continue to push eastward, which will help keep
things rather cool across the area for the last few days of the work
week. High pressure will eventually build into the area which will
mean dry weather to end out the week. Plenty of low level moisture
rotating around the sfc low in the eastern Great Lakes will mean
more cloudiness though, especially in our northern and eastern
sections.

While models start off pretty consistent with the upper level
pattern to start out the weekend, they diverge fairly quickly.
Models are in agreement that a closed upper level low will develop
over the southwestern U.S. on Friday. How this system evolves as it
slides eastward becomes a problem. The GFS/GEFS/Canadian continue to
indicate a split flow pattern with a shortwave trough racing east
across the Plains and into our region by Saturday night/early Sunday
and the closed upper low shifts south and eventually lifts northeast
into TX and impacting our area by Monday night. So that provides us
two opportunities for precipitation, with the first being fairly
light.

The ECMWF does not indicate this split flow pattern and simply
brings an upper trough across the central Plains Friday night into
Saturday night. Strong cyclogenesis develops over the lower
Mississippi Valley by Sunday. This sfc low shifts
northward/northeastward bringing us precipitation Saturday night
through Sunday night.

So even though there continues to be discrepancies in the models,
the next chance for precipitation could arrive Saturday night but
would be light so POPs will be only slights.  However, the timing of
when the main closed low/upper trough swings through remains a
problem...so POPs for Sunday will continue to be low but not
nonexistent. Still plenty of time for things to stabilize.

High temperatures should generally remain in the 40s for the most
part. A few locations could reach close to 50 degrees during the
extended period. Lows will be in the upper 20s to lower 30s.

&&

.AVIATION...
Issued at 557 PM CST Mon Nov 28 2016

The fine line has cleared the area, but the bubble high pressure
behind it has created some nice southeast winds in its wake.
Figure on some 15-20kts southeast flow for a few hours beginning
near the back edge of the precipitation shield which should be
clearing KPAH at 00Z. With west southwest winds off the surface,
threw in LLWS until the surface winds veer back to southwest later
this evening.

There has been pretty nice improvement to VFR conditions for the
most part behind the main convective line, but there are signs of
low clouds behind the upper cloud shield over southeast Missouri
and southward into eastern Arkansas. Once the winds veer to
southwest, we should be advecting better low-level moisture to the
region, which the GFS and NAM hit hard for IFR or lower fog and/or
low clouds. Took each site to IFR levels as a first guess mainly
overnight into Tuesday morning. South winds should pick back up by
late morning and help with the clearing process.


&&

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

$$

UPDATE...Smith
SHORT TERM...GM
LONG TERM...CW
AVIATION...DRS


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