Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 081720
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1220 PM EST Sun Dec 8 2013
...Updated Aviation Discussion...
Issued at 1212 PM EST Sun Dec 8 2013
Wintry mix has turned to rain in the south and has dissipated to
just some patches of light freezing drizzle in the north/west, so
have canceled the advisory for the Bowling Green and Louisville
areas. Have replaced it with a Special Weather Statement for the
light patchy FZDZ.
Issued at 835 AM EST Sun Dec 8 2013
Ongoing winter weather event is panning out pretty much as expected
thus far across the region. The latest reports that continue to
filter in show up to 0.2 tenths of an inch of ice on trees and
elevated surfaces, with perhaps up to 0.25 inch in isolated
locations. The highest threat for icing up to 1/4 inch will be on a
line from Logan/Butler counties northeast to Clark/Madison/Garrard
counties. Thus far, reports indicate that side roads are a bit
icy in these areas, but main roads seem to be doing okay. Given the
short duration of the event (latest HRRR shows precip exiting most
locations by 19Z) and locations receiving the icing now will likely
get above freezing in the next couple of hours, will hold off on any
ice storm warning product for now. Certainly a high-end advisory
event in some areas, but impacts thus far continue to warrant
leaving the advisory as is. Updates already out.
.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 (18Z TAF Update)...
Updated at 1218 PM EST Sun Dec 8 2013
The wintry mix has become very light across the region this
afternoon, but a prolonged period of IFR cigs or even LIFR cigs
appears increasingly likely tonight. These LIFR ceilings have already
moved into KBWG, and will likely affect KLEX as well. As another
disturbance pushes in from the southwest overnight, additional
low-level moisture will work into the region. This will cause
ceilings to remain IFR or LIFR through the overnight period, with
even a few light showers possible around KLEX or KBWG. KSDF will
be further removed from the deeper moisture overnight, so just
expect IFR cigs and perhaps some isolated drizzle. Winds will be
shifting from easterly to southerly to westerly by Monday morning.
Wind speeds will be generally light, around 7 knots or less.
Ceilings should slowly improve throughout the day on Monday,
lifting to MVFR thresholds by the mid to late morning hours.
KY...WINTER WEATHER ADVISORY until 6 PM EST this evening FOR
WINTER WEATHER ADVISORY until 3 PM EST this afternoon FOR KYZ067.