Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 251943
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
243 PM EST Thu Dec 25 2014
.SHORT TERM (Now through Friday Night)...
Issued at 232 PM EST Thu Dec 25 2014
High pressure moving from Georgia to the Carolina coast will keep
our short term weather very quiet. Once the last clouds move out of
the Blue Grass early this evening, we`ll have a mostly clear night
with temperatures dropping to around the freezing mark. Folks
around Lake Cumberland and Dale Hollow could see some patchy valley
fog as the sun comes up.
With lots of sunshine tomorrow, the mercury will climb into the
50s. Friday night we will be in return flow behind the eastern high
and may begin to see an increase in cloudiness ahead of an
approaching storm system over the Mississippi Valley. Lows will
range from the lower 30s in the eastern valleys to the lower 40s
.LONG TERM (Saturday through Thursday)...
Issued at 240 PM EST Thu Dec 25 2014
The synoptic pattern at the start of the long term period will
feature a rather amplified regime across the CONUS, with an east
coast ridge and a western trough. This pattern will flatten out
through the long term period, leaving the Ohio Valley within a
rather benign regime for the first part of next week.
The main focus of the long term period will be on a storm system
which will eject out of the aforementioned western trough. In
response, a surface low will deepen across the Great Lakes on
Saturday, helping to sharpen a cold front across the Midwest. Ahead
of the front, showers will develop within the warm conveyor belt and
associated isentropic ascent. Moisture transport does not look all
too impressive, and the better synoptic forcing will pass well to
the north, therefore, will not go with categorical pops quite yet.
The cold front will pass through early Sunday morning, causing
temperatures to fall into the 30s behind it. The cold air will be
rushing in as the better moisture is exiting, thus do not expect
much in the way of any wintry precip on the back side of this
system. The system is not dynamic enough and there is not a good
source of polar air, thus think this is just going to be a rain
event for the region. Rainfall amounts will range from 0.25-0.75
The 25/12Z GEM remains the only deterministic model hinting at a
more amplified pattern and a resultant stronger secondary low
developing along the front Sunday night into Monday, which would
spread additional precip back northwest into the region. However,
the deterministic ECMWF/GFS and the GFS/ECMWF ensembles continue to
shy away from this idea, thus will continue to dry the forecast out
for Sunday night into Monday. The best chance for any precip would
be across far south-central KY.
Otherwise, the remainder of the long term period will feature a
strong 1050+ mb surface ridge sliding into the middle of the
country. The influence of this ridge will persist Monday through at
least the middle of next week, bringing tranquil conditions.
Daytime highs Monday through Wednesday will generally be in the
upper 30s and 40s, with overnight lows in the 20s and lower 30s.
.AVIATION (18Z TAF Update)...
Issued at 1204 PM EST Thu Dec 25 2014
The western edge of a large field of stratocu with bases right
around 3000 feet has been making progress eastward today, and should
continue to do so. Will attempt to time the clearing into the
airports this afternoon at BWG/SDF and early this evening at LEX.
After that, high pressure over the southeast U.S. will provide us
with fair weather. Some model data hint at some low cloud
development toward morning, but even if any clouds do form (which is
doubtful) they shouldn`t become a ceiling. There is also a hint of
some patchy fog possible in the morning, but winds should stay up
enough and dew point depressions large enough to prevent issues at