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Area forecast discussion 
National Weather Service Paducah Kentucky
1144 PM CST Wed Dec 17 2014

Update...
issued at 1144 PM CST Wednesday Dec 17 2014

Updated aviation section for 06z taf package.

&&

Short term...(tonight through friday)
issued at 200 PM CST Wednesday Dec 17 2014

Midday trends...pcpn is developing a little bit ahead of
schedule...but the hrr and the 12z Euro are both pretty doing a
decent job of picking up on it.

Radar mosaic shows mainly rain into northwest Arkansas/southwest MO, with
an isolated report of -sn/-ip noted. Modeled thermodynamic trends
from yesterday to today continue to show impressive warming aloft
as the pcpn field advances eastward. Thus, any incoming pcpn this
evening into semo/Ozarks this evening would appear to be rain, or
a mix of rain/sleet. Even with a slightly quicker than model
speed, we do not foresee an eastward advancement of the pcpn past
roughly the MS river, prior to midnight.

After midnight, some nocturnal cooling in the boundary layer may
allow for the pcpn to change over in the south to a snow/sleet or
rain/sleet mix. Toward morning, as surface temps near 32f, and
the warm nose from the 850 swlys grows, this could perhaps include
even a chance of fzra for isolated locales roughly along a just
south of cgi-to near pah-to just north of hop line. The westward does
suggest a connect the dots possibility for a hundredth of an inch
of --fzra in this vicinity, so we included its slgt chc/chc
mention for a brief 1-2 hr period in that area. South of there
should see rain/sleet and north of there, snow/sleet cutting off to
flurries or no wx, as drier/colder air aloft also cuts off the -10
to -20c ice nuclei. This occurs rapidly after about 09z and almost
entirely by mid to late morning.

With total snow/ice accums remaining less than an inch and collab
agreement not to expand sgf or lsx inherited advisories eastward,
we'll lay off the headline at this writing, continuing our
inherited Special Weather Statement/severe weather potential statement approach. This could change if
conditions/evolutions this evening suggest a higher qpf or colder
thermodynamic profile to warrant wintry wx impacts to travel,
which at this writing, seem to be nil.

Long term...(friday night through wednesday)
issued at 154 PM CST Wednesday Dec 17 2014

We have two systems to deal with during this time period. First
system will develop over south Texas Thursday night into
Friday...and then move east Friday night. Models have been in good
agreement on the sfc low placement and timing thus far. But models
have been trending further south with the quantitative precipitation forecast. Most of the
precipitation will fall across our southern counties, where we
already have high pops forecast for Friday night. Chances for
precipitation diminish greatly as you go northward.

The thermal profiles are where the differences have been and
continue to be. One thing to note though, is that the GFS has
trended colder across the northern areas. So that gives some
confidence that if we even get precipitation up there, it will
probably be snow, albeit light. As it always seems in our area,
there will be some type of transition zone of rain and/or snow, and
maybe some sleet, and then all rain near the Tennessee/Kentucky borders. This
looks like a light event nonetheless.

This system will be departing by Saturday morning, with best chances
for precipitation in the east and maintaining the rain-snow line
similar to Friday night. The rest of the weekend looks dry with
slightly below normal temperatures.

The next system to approach US just a few days before Christmas,
looks to bring US another round of precipitation. Indications right
now are that rain will be possible Monday night into Tuesday as a
deep upper level trough moves toward and then into the area. It does
appear possible, depending on how fast the cold air filters in, we
could have some of the rain change to snow late Tuesday. However,
what happens later on, is not well handled by the models. The GFS
wants to develop a large closed low over the Great Lakes and keeps US
in cold northwest flow with occasional chances for light snow. The
European model (ecmwf) develops the upper low over our area which gives US better
chances for snow Tuesday night into Wednesday. Will continue to
monitor.

&&

Aviation...
issued at 1144 am CST Wednesday Dec 17 2014

At kcgi/kpah, VFR cigs will drop to MVFR and IFR with the onset
of rapl changing to snpl, with brief dips to IFR possible. Vsbys
will be VFR and MVFR. For kevv/kowb, cigs will be VFR dropping to
MVFR, with kowb having a better chance of seeing snpl after 10z,
with both sites seeing -sn after daybreak. Precip will end by 18z,
with an increase back to VFR conditions.

&&

Pah watches/warnings/advisories...
Illinois...none.
MO...none.
In...none.
Kentucky...none.
&&

$$

Aviation...rst

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