Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 012324
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
624 PM EST Sun Dec 1 2013
...Updated Aviation Discussion...
.SHORT TERM (Now through Monday Night)...
Issued at 259 PM EST Sun Dec 01 2013
The thin layer of stratocu has scattered out along and north of the
Ohio River this afternoon. Meanwhile, broken to overcast skies
remain across south and east central Kentucky. Do expect this
scattering/clearing line to make more progress southeast through the
early evening, possibly to a Bowling Green to Lexington line. This
will occur as the weak isentropic lift component continues to shift
southeast. Also of note, weakly defined frontal boundary is
currently located from the eastern Great Lakes, to near St.
Focus will shift to south central Kentucky overnight for some very
small chances of drizzle and/or measurable light rain. Slightly more
low level moisture will pool into the area ahead of a weak wave that
is currently over the western high Plains of CO/KS. This wave will
quickly move ESE through the zonal flow to the mid Mississippi River
Valley by shortly after Midnight. Expect a few pockets of light rain
or drizzle to be possible south of the Ohio River with this feature.
Did include a 20% chance of measurable rain mention, and that is
likely a bit generous. Otherwise, expect mostly cloudy skies tonight
with the increasing low level moisture. Questioning whether southern
Indiana will see the redevelopment of low level cloud cover as best
weak isentropic lift and shallow moisture will be south of the
river. However, models are bullish with the low level stratocu so
will continue to forecast this due to the proximity of the weakening
frontal boundary just to the north. Expect lows generally in the low
Will keep the low chances of light rain or drizzle across south
central Kentucky on Monday. Best chances of this precipitation will
be in the morning hours. Expect mostly cloudy skies once again, with
perhaps a few breaks in the clouds at times. Look for highs mainly
in the mid 50s. Best chance for partly cloudy skies will be near the
Bowling Green region monday afternoon.
Monday night is tricky since we will still have some low level
moisture in place and a more pronounced isentropic lift component
working in from the southwest toward dawn as a weak LLJ begins to
respond with cyclogenesis over the high Plains. Will leave the
forecast dry due to the lack of more robust low level moisture,
however chances for some drizzle could very well extend into Monday
night near BWG. Look for lows generally in the low and mid 40s.
.LONG TERM (Tuesday through Sunday)...
Issued at 250 PM EST Sun Dec 1 2013
Tuesday we should see mostly cloudy skies as we remain in the warm
moist flow ahead of a low over the Central Plains. A few of the
models are spitting out some light precip within the broad scale
lift in this zone, but still am not convinced that it is worth
mentioning in the public forecast at this time. Despite the cloud
cover, temperatures will warm to several degrees above normal, a
trend which will remain until the forecast slow-moving front for the
rest of the work week passes.
Speaking of that front, it looks to drift into our northwest
forecast area late in the day Wednesday. Steadily increasing
moisture ahead of it will bring a slight chance of rain Tuesday
night, with chances increasing Wednesday and Wednesday night. The
trend in the models as far as pushing the front through our forecast
area has been faster. However, it still hangs up over the
Appalachians Thursday into early Saturday. With multiple
disturbances riding along the southwesterly flow aloft energizing
this boundary, we look to have a good shot of precip on the back
side of the front through Friday night.
Precip type through the event will start off as all rain. Given the
faster progression of the front to our southeast, forecast QPF for
the event has started to come down over the north, which should ease
our threat for nuisance flooding there. The southern zones are still
running high though, so still will have to keep an eye on rainfall
totals. For now have totals from Tuesday night through Friday night
of 2-3 inches down there.
The trickier part of the forecast will come with how much cold
air filters in behind the front and what kind of p-type issues we
have Thursday night through Friday night. The set up looks like one
where a thin stripe within the rain band will have to deal with
freezing rain/sleet, given the warm air riding aloft above the
surface. CIPS Analog guidance from 00Z indicated points to our north
would have to deal with this threat, but with the faster progression
in the 12Z models, we may get this closer to the Ohio River. For now
have gone with a wintry mix over southern Indiana for Thursday night
and Friday, with our far northern stripe of counties having the best
chance of switching over to all snow during the day Friday. Then as
the system starts departing Friday night have lighter snows moving
farther south, with a rain/snow mix across our southeast zones.
The GFS and the 00Z Euro both have another wave enhancing the front
for another round of precip late Sunday into Sunday night. Given
cold air in place have snow as the predominate precip type, though
for now totals are very low. Going a little further into the
extended the 00Z Euro lingers this front and brings another round of
soaking rains Sunday night through Monday night. Certainly an
unsettled period and lots to watch over the next several model runs.
.AVIATION (00Z TAF Update)...
Updated at 624 PM EST Sun Dec 1 2013
This is a ceiling/vsby forecast, and model data are conflicting, so
confidence is not high in this TAF package.
VFR conditions prevail across central Kentucky as of this writing.
The overcast in the BWG/LEX areas is expected to remain fairly
steady...perhaps sliding just a bit more to the southeast.
At SDF the stratocu deck cleared out earlier. Some model data
suggest that these clouds may fill back in, and satellite does show
a few clumps of clouds here and there along and either side of the
Ohio River. For now will go without a low ceiling in the TAFs,
instead bringing in AC/CI currently over the mid-Missouri Valley.
Even if the lower clouds do fill back in, they should remain just
Fog is another question for tonight. Some models are hitting fog
pretty hard during the usual low vsby hours either side of dawn.
However for now will count on ceilings to keep dense fog chances
slim, and will simply bring in some MVFR vsbys for a few hours.
On Monday low clouds are expected to stick around as a weak cold
front along the Ohio River transitions into a weak warm front.
Ceiling heights will be right around the VFR/MVFR border.
The clouds could drop a sprinkle or two but nothing of any
consequence. More significant rains tonight will be to our south in
the Tennessee Valley, and tomorrow to both our north and our south.
Winds will be light and variable.