Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 031428

Area Forecast Discussion
National Weather Service Louisville KY
928 AM EST Sat Dec 3 2016

.Forecast Update...
Issued at 925 AM EST Sat Dec 3 2016

Mid-level stratus deck persists this morning. It showed up nicely in
the morning lows this morning, with readings in the upper 30s to
around 40 over northern KY and southern IN and readings around 30
over south KY.  GOES-R MVFR probability maps show this layer well,
with little movement. Forecast soundings from the RAP and NAM
indicate this moist layer drying up from above in the 18-21Z time
frame, but cloud deck above will keep us mostly cloudy the rest of
the day.

Those high clouds will thicken up tonight. Model timing still looks
good for light precip to begin later this evening over our KY/TN
border and then progressing northward. May make a later tweak this
morning as 12Z models pour in.


.Short Term (Now through Sunday)...
Issued at 220 AM EST Sat Dec 3 2016

An early morning analysis showed surface high pressure across the
mid MS and lower OH river valleys. Aloft, a deep closed low was
centered along the AZ/Mexico border, which was helping to push a
plume of mid/high clouds across the southern Plains into the TN
Valley. Locally, IR satellite showed a stratus deck across Indiana
and northern KY with just high clouds across southern Kentucky.
Readings were in the mid 30s to lower 40s.

For today, expect a mainly cloudy but dry day. There will be a small
diurnal rise in temperatures today with highs in the low/mid 40s
across southern Indiana to mid/upper 40s across southern Kentucky.
Increasing isentropic lift with the approach of the upper level
shortwave energy will break out light precipitation across Tennessee
this evening. This will move into southern Kentucky after sunset
then spread north/northeast through the night. Precipitation type
will be mostly rain but a few wet snowflakes may mix at the onset,
especially across southern Indiana and parts of northern Kentucky
however no accumulations or impacts are expected with very warm
surface ground temperatures. Lows will be generally in the 32-38

Weak but persistent isentropic lift will keep pumping more moisture
into the region on Sunday along with another mid level wave coming
out of Missouri and Illinois later in the day. This will keep the
threat of light rain throughout much of the day. Overall, amounts
are expected to be 0.25 of an inch or less, with the highest amounts
focused along the KY/TN border. High temperatures will again be
stuck in the 40s.

.Long Term (Sunday night through Friday)...
Issued at 225 AM EST Sat Dec 3 2016

An unsettled week weather-wise with several systems to focus on
early this morning.

In the wake of Sunday`s rain maker, a brief lull is in store Monday
morning as a quick moving high pressure system slides across the
region. Lingering low-level moisture and a light wind field may
promote patchy fog development early Monday morning, otherwise plan
on temperatures starting out in the mid/upper 30s.

A strong, more organized upper level shortwave and surface low
pressure will kick out of Texas and lift toward the region late
Monday into Tuesday. This well-advertised system will spread rain
from the south/southwest into the area Monday evening and especially
throughout the day on Tuesday. Some heavy downpours will be
possible. All of the available forecast guidance is in reasonable
agreement so precipitation chances remain in the 80 to 100 percent
range Monday Night and Tuesday. Soundings do show some elevated
instability across parts of central Kentucky so the isolated thunder
mention looks good as well. Total rainfall for this event is
currently projected to be around 1 inch for most of the area.

As that system lifts through the region, the focus turns to the
north as a strong upper level closed low drops out of Canada into
the Upper Midwest. Pieces of energy will pivot along the base of the
upper trough while at the surface, strong Canadian high pressure
dives southward. There remains some differences in timing between
the GFS, GEM and ECMWF solutions showing a strong cold front passage
between Wednesday night and Thursday afternoon. The ECMWF is a
slower, wetter but warmer solution while the GFS and GEM are less
phased which results in lighter QPF but bringing the cold air in
sooner. A model consensus blend was used which shows low chance
precipitation chances with mostly rain in the forecast though the
GFS solution would support some snow on the back end of the cold
front passage.

Regardless, the main highlight will be the sharply colder
temperatures in its wake, beginning potentially Thursday but more
likely Thursday Night and Friday. High temperatures on Friday may
struggle to break 30 degrees in many places after starting out the
morning in the teens.


.Aviation (12Z TAF Update)...
Issued at 616 AM EST Sat Dec 3 2016

Pesky low clouds continue over SDF and LEX. These clouds have not
been handled well by the forecast models and now are difficult to
see beneath higher clouds on satellite pictures. At this time the
thought is that these clouds will continue for several more hours
before finally letting go. There may be a brief period shortly after
sunrise where they scatter out before filling back in for the rest
of the morning, before breaking up for good by midday. Ceilings
should be just barely VFR.

For the rest of the TAF period higher clouds will stream in from the
southwest ahead of an approaching storm system. Clouds will slowly
lower and thicken as the TAF period progresses. Some very light rain
could fall at BWG in the last few hours of that site`s TAF period,
and sprinkles or flurries may occur at SDF in the planning period.


.LMK Watches/Warnings/Advisories...


Short Term........ZT
Long Term.........ZT
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