Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 080800
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
300 AM EST Sun Dec 8 2013
.SHORT TERM (Now through Monday)...
Issued at 300 AM EST Sun Dec 8 2013
...A light wintry mix possible this morning...tending to change over
to just light rain by afternoon across south central Kentucky...
Upper air pattern shows a broad positively tilted trough across the
Rockies, with southwesterly flow extending from Oklahoma through New
England. Lift, associated with the right entrance region of a
departing jet, coupled with moisture overrunning a nearly stationary
boundary over Tennessee, will bring light mixed wintry precipitation
this morning over central Kentucky.
Forecast soundings show a warm layer around 850mb nosing northwards
across southern Kentucky, and eventually into the Bluegrass.
However, northeasterly winds will keep surface temperatures near
freezing along the Tennessee border, and in the mid to upper 20s
across central Kentucky.
Light mixed sleet and freezing rain will overspread southern
Kentucky during the predawn hours, and slowly move northeast towards
the Bluegrass and along the Ohio River around dawn or shortly after.
Towards Interstate 64, and across the Bluegrass, mixed precip may be
preceded by a period of light snow, with minor accumulations. By
noon, temperatures across our southern counties will slowly rise
above freezing. Any mixed precip should change over to rain or just
drizzle across the Bluegrass by mid to late afternoon. Along the
Ohio River, where snowcover remains, temperatures will struggle to
exceed freezing even by late afternoon.
Will continue with a winter weather advisory for light sleet and
icing across the central Commonwealth, and will likely allow it to
expire by early afternoon across our southern counties. We should
note that any icing or glaze will be light, as precipitation amounts
will likely stay under 2 tenths of an inch near the Ohio River,
ranging to maybe one half inch near the Lake Cumberland Region,
where temperatures will first rise above freezing. Despite light
precip amounts, any light glaze will adversely affect travel due to
antecedent cold pavement and ground.
Light precip will likely change over to just drizzle by
mid-afternoon as moisture become more shallow by evening. Continued
light rain may continue near Lake Cumberland, where a continued
fetch of moisture from the southwest may allow steadier
precipitation. Highs late this afternoon will range from the lower
40s near Lake Cumberland to the lower 30s across southern Indiana.
As this first wave passes, moisture will become more shallow, but
will continue saturated at low levels. So...expect cloudy skies this
evening and overnight, with maybe even some light fog and drizzle.
Temperatures won`t fall to much tonight, with lows not too far from
freezing south and east of the Ohio River.
Some partial clearing may arrive Monday afternoon, especially across
southern Indiana, with highs remaining in the 30s.
.LONG TERM (Monday Night through Saturday)...
Issued at 255 AM EST Sun Dec 8 2013
This period will begin with surface high pressure ridging across or
just north of the Ohio River. Aloft we will have a southwesterly
flow with an elongated vortmax stretching from southeast Ontario to
Oklahoma. Similar to yesterday`s 00Z model runs, today`s GFS/GEM/NAM
all have precip across our southeast early Tuesday as well as a
separate band of precip over southern Indiana, within the right
entrance region of a 180kt upper jet centered over Lake Erie. This
band, of what likely would be snow, is a little farther north than
what was forecast yesterday. The repetition in features, as well as
adding the new ECMWF into the mix, gives me enough of a signal to at
least put in a slight chance of snow across my north early Tuesday
and into the day. As for precip type across our southeast, that
mostly looks like snow from a quick look at soundings. We may warm
enough at the surface for a rain/snow mix. A quick look at forecast
totals for now indicates a sub-advisory event.
Another impulse moves through here Wednesday night, with a few of
the models hinting at low QPF just to our north. May get some
flurries out of this system across the north, but will leave
forecast dry for now.
High pressure on the back side of that system will shift east of our
area Friday, allowing for some southerly winds to try and start a
warmup for the weekend, at least closer to normal. With that warmup
will come another surge in moisture, bringing precip chances back
into the picture. Temperatures are at a range close enough to put in
a rain/snow mix Friday night through Saturday.
.AVIATION (06Z TAF Update)...
Updated at 1205 AM EST Sun Dec 8 2013
Light mixed wintry precipitation will arrive from the southwest and
fill in over central Kentucky during the mid-morning hours.
Light sleet and freezing rain will begin shortly before 10z
as ceilings fall to MVFR. Precipitation rates will stay light enough
so that visibilities will stay in the upper MVFR range. Ceilings
will likely lower to IFR as freezing drizzle or light freezing rain
changes to just drizzle by around noon. IFR ceilings will continue
this evening and tonight as light drizzle continues until early
Light sleet, possibly mixed at first with light snow will begin near
or shortly after 12z. This will change into light freezing rain
which will continue through the morning hours, eventually changing
to light rain or drizzle by mid afternoon. IFR ceilings are likely
this evening and overnight.
Light sleet, possibly mixed at first with light snow will begin
shortly after 12z. Light sleet or freezing rain will likely continue
through the mid-afternoon hours. Again, precipitation rates will
stay light, so that ground-based visibilities will stay high in the
MVFR or even VFR range today. IFR ceilings are expected this
afternoon and tonight.
Northeast winds of 5 to 10 mph tonight will veer to easterly by
morning. Winds will become southerly at around 5 mph this evening.
KY...WINTER WEATHER ADVISORY until 3 PM EST /2 PM CST/ this afternoon
WINTER WEATHER ADVISORY until 6 PM EST /5 PM CST/ this evening