Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 182313
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
513 PM CST Wed Jan 18 2017

.UPDATE...
Issued at 512 PM CST Wed Jan 18 2017

Updated Aviation discussion for 00Z TAF Issuance.

&&

.SHORT TERM...(Tonight through Friday night)
Issued at 249 PM CST Wed Jan 18 2017

The main concern in the short term portion of the forecast is a
storm system pivoting north northeast out of the southern Plains
Thursday and through the mid-Mississippi Valley Thursday night.
Ahead of it, winds will become easterly and lots of elevated
moisture will return to the region beginning late tonight. The
overall trend in the 12Z guidance is for a slower arrival time for
the elevated showers. The HRRR has been consistent in killing off
any light shower activity moving northeast out or Arkansas this
evening.

Generally followed the 12Z GFS and ECMWF for the placement of PoPs
for Thursday and Thursday night. The models are indicating a
pretty sharp western edge to the heavier rains, so western and
northwestern portions of the region may see a quick hit of some
showers late tonight and Thursday morning, and then dry out fairly
quickly.

The 12Z guidance is in decent agreement in developing some meager
elevated instability, so will keep a slight chance of thunder
going Thursday into Thursday evening. Do not feel that enhanced
rainfall rates will persist long enough at any one place to cause
much in the way of flash flooding. However, given the saturated
soil conditions across the region, and in particular, west
Kentucky, did give serious consideration to a Flood Watch for
Thursday.

6 hour FFG values over west Kentucky are well over 2 inches, so
the 1.25"-1.6" currently forecast over a 12 hour period in west
Kentucky should not cause major problems. The FFG may be a bit
optimistic, so will give the areal flood concerns a decent write
up in the HWO. The bulk of the rains should hold off until the
midnight shift forecast is complete, so there is still time for a
Watch or at least an SPS. Needless to say the forecast rainfall
will only aggravate river flooding across the region.

As this upper system lifts north and weakens, another storm system
will emerge into the central Plains Thursday night and Friday. It
will actually lift a warm front north through our area late
Thursday night and Friday. There could be some shallow instability
that could be just deep enough to support a few showers near the
front on Friday, so will have 20% PoPs over at least the
west/northwest half of the area through the day. Friday night
will actually be dry. Yeah!

For tonight, the low clouds have cleared over much of southern
Illinois, but thicker high clouds will keep things more cloudy
this evening than clear. The low clouds should lift back to the
north quickly by midnight, and despite easterly winds, a non-
diurnal temperature trend is a good bet. Much of the area will
likely see lows at some point this evening, with steady or
slightly warming temperatures after midnight.

It will be mild through the period, with the warmest conditions
expected behind the warm front on Friday. Much of the area should
climb above 60 Friday.

.LONG TERM...(Saturday through Wednesday)
Issued at 249 PM CST Wed Jan 18 2017

Main story in the long term period is the unseasonably warm
temperatures and a storm system that will impact our area over the
weekend.

The region will reside in southwest flow aloft on Saturday, with
warm, moist air being transported into the area. Weak forcing ahead
of energy moving into the Southern Plains on Saturday should result
in at least isolated to scattered showers through the day, although
many places may end up dry for most of the day. The main piece of
energy will move toward the area Saturday night through the 1st part
of Monday, with precip chances increasing during this time. The peak
time period for best areal coverage appears to be Sunday into Sunday
night. From Saturday afternoon thru Sunday, models are hinting at
enough instability for thunder potential. With sufficient MUCAPE,
marginally negative showalters, and LI`s from 0 to -3, went ahead
and included slight chance of thunder. QPF from the weekend system
is expected to be highest over western KY (roughly 1-1.50"), to
around 0.50" across western and northwest counties.

The system is expected to pivot out of our area sometime on Monday,
although exact ending time is somewhat in question. Drier weather is
then expected Monday night into the day on Tuesday as upper level
ridging moves in. Discarded the 12Z ECMWF for now, as it came in wet
for Monday night/Tuesday morning for the 1st time and only model
showing it. Troughing over the western states will work east by
midweek, bringing a cold front into the area. Currently the best
forcing looks to be well north of our area, closer to the sfc low
track, and models aren`t in great consensus on the amount of
moisture moving through our area. So for now only pops late in the
period are slight chance for Tuesday night.

As for temperatures, Saturday will be the warmest day with highs in
the 60s areawide. Would not be surprised to see a few locations
touch 70, especially if any breaks for sunshine occur. Record highs
may be challenged (Paducah: 70, Evansville: 71, Cape Girardeau: 68).
Temperatures will slowly migrate down heading into next week with
50s common Monday thru Wednesday, still some 10 degrees above
normal. There has been good consensus with long range guidance
hinting at a cooler pattern setting up later next week and possibly
lasting thru the end of the month, as troughing sets up over the
eastern half of the country.

&&

.AVIATION...
Issued at 512 PM CST Wed Jan 18 2017

Open Gulf stream/fetch readily depicted by both Satellite/Radar
will lead to lowering CIGS and VSBYS tonight-tmrw, with IFR
conditions at times. Some improvement noted late in the planning
period for KCGI/KPAH as conditions worsen eastward (KOWB) same
time, given the west to east translation of the overall system.

&&

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

&&

$$



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