Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 031949
Area Forecast Discussion
National Weather Service Louisville KY
249 PM EST Sat Dec 3 2016
.Short Term...(This evening through Sunday night)
Issued at 230 PM EST Sat Dec 3 2016
Gentle, but deep-layered, isentropic lift will move into the region
overnight. Precipitable waters will increase slowly from the south,
to around an inch, roughly double the current value, by 12Z Sunday
down along the KY/TN border. The combination of this increasing
moisture and that lift will mean a chance for precipitation, albeit
relatively light. Forecast soundings indicate a steady saturation,
resulting in lowering high cloud bases tonight. Freezing levels will
drop a little tonight, but with the warming in the lower layers,
expect any initial mix of rain/snow on the northern edge to become
rain. Surface temperatures around daybreak will hover near freezing
in our Bluegrass and southern Indiana counties, but any precip
should be light enough not to cause any driving hazards, especially
with relatively warm road temperatures.
For the day Sunday, deeper moisture briefly departs, as we get
gapped between a vortmax crossing by to our north and the energy
heading through the Deep South. Despite this gap, the models keep
light QPF fields in through the day, perhaps indicating some
drizzle/light rain showers. Given the cloud cover, it will end up
being a another raw day, with temperatures likely rising only to the
mid to upper 40s, a little below normal for early December.
That precip will kick east of here Sunday night, with high pressure
building in behind it. Cannot rule out some linger light drizzle and
or patches of fog overnight. Expect temperatures to fall again into
the mid to upper 30s.
.Long Term...(Monday through Saturday)
Issued at 240 PM EST Sat Dec 3 2016
Models remain remarkably consistent in dealing with systems in the
first half of the work week, but then the ECMWF solution continues
to have a wetter system Wed. night and Thursday. Whatever the
outcome of that system, we`re still looking at a significant cool
down to close out the work week and head into the next weekend.
First off, we`ll start with high pressure shifting to the Mid
Atlantic states Monday, as our next system approaches from the
southern Plains. Stronger isentropic lift will accompany this
system, bringing a solid area of rains, likely up to an inch.
Surface low pressure will cross the state some time Tuesday, with
breezy conditions ahead of and behind it.
Large surface high pressure will ridge in from the southwest Canada
as a large upper low spins over south central Canada Wednesday. The
latter feature actually has a similar depiction in the various model
guidance, but 00Z Euro has continued its solution with another
surface low crossing our region. The 12Z Euro has backed off on
precip a little, as well as with the strength of that low. Still,
with the cold air, we`ll have a brief potential for snow on the
That cold air will mean highs Thursday struggling in the lower 30s
and Friday likely staying in the 20s. Lows Friday and Saturday
mornings will be the coldest of the season, in the teens.
.Aviation...(18Z TAF Issuance)
Issued at 1235 PM EST Sat Dec 3 2016
Low clouds continue to hold in tough at SDF and LEX at this time. A
recent pilot report over LEX indicated a base at 3100 ft and top at
3900 ft. Despite the cloud thinness, model soundings have continued
to show this moisture trapped under a significant subsidence
inversion. Models have been too quick to scour out the clouds up to
this point. However, with mid and high level moisture streaming
northeast at this time over the area ahead of the next system, these
clouds should finally begin to break by late afternoon at SDF and
this evening at LEX. Surface winds will be light north to northeast.
For tonight, clouds will lower again from southwest to northeast
over central KY as the next weather system advances toward the area.
Light rain showers will first affect BWG overnight and SDF and LEX
around daybreak. Vsbys and cigs will eventually deteriorate into
MVFR as showers overspread the area. Vsbys and cigs during the day
Sunday should continue to lower, probably becoming IFR (at least
cigs) at BWG by mid/late morning, and in the afternoon at SDF and
LEX (after the end of the current TAF valid period at LEX). Surface
winds will become east then southeast at 5-10 kts.