Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 161940

140 PM CST Tue Dec 16 2014

.SHORT TERM...(Tonight through Thursday)
Issued at 130 PM CST TUE DEC 16 2014

The primary forecast challenge is the Wednesday night system. With
the new 12Z ECMWF just trickling in at this writing, we see a
confirmation of a warmer introductory Pop Wednesday evening in the
Ozarks, while the overnight thermo profile remains largely
unchanged across the broader CWA from the previous forecasts.
Soundings increasingly suggest a warm elevated layer between 3 and
6 or 7 K feet during this time frame, mainly for our southern tier
of counties, and there is broad collaborative agreement to include
a mention of sleet there. The net qpf result is a continued,
generally inch "ish" forecast (or less) of snow for the Wednesday
night-Thursday morning time frame...and this is confirmed by WWD.
Pops now run into the high likelys for the peak pop time frame of
06z-18z Thu.

.LONG TERM...(Thursday night through Tuesday)
Issued at 130 PM CST TUE DEC 16 2014

To start off the long term, a system will move east across the Gulf
coast states Friday into Saturday. Model agreement has improved
considerably over the past 24 hours. There is not much model
difference in the track of the surface low, which moves east across
the Gulf coast states. Now that agreement exists on the path of the
system, there is very little difference in low level temps. The 12z
ecmwf has trended a little warmer, and it now keeps surface temps
above freezing through the entire event in much of western Kentucky.
Looking at a blend of the gfs and ecmwf, mostly snow is forecast
north and west of the Ohio River and mostly rain down toward khop.

Due to the southern track of the system, precip amounts will be
lower in the colder air north of the Ohio River. Heavier precip
along the Tennessee border should be offset by warmer temps and a
shorter duration of snow. Based on a blend of 12z model temps and
qpf, this does not appear to be a high impact event. However this
system is still more than 72 hours away, so there will likely be
adjustments to the forecast.

The gfs timing of the system slowed down to come into better
agreement with the ecmwf timing. The window for most of the precip
should be mainly Friday night into Saturday morning.

A surface high will move quickly east across our region on Sunday,
followed by milder southwest winds on Monday.

The longer range ensemble means /gfs, ecmwf, naefs/ all develop a
deep 500 mb trough or closed low over the Great Lakes region on
Tuesday. This system will draw significantly colder air
southeastward across the central and eastern states.


Issued at 130 PM CST TUE DEC 16 2014

With the parent cyclone departing further east, we should
ultimately see the lower clouds scatter. However, with the
nightfall inversion approaching, some lower trop moisture may get
trapped and be harder to disperse (particularly further east at
KEVV/KOWB). Thus we may see MVFR cigs continue into/thru the
evening, but by late tonight-early tmrw, believe drier air working
down the column could disperse. Either way, by the planning period with
some diurnal mixing, should see them scattered out by then as high
clouds begin to stream in ahead of the next system.



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