Area Forecast Discussion
Issued by NWS Louisville, KY

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KLMK 100449

Area Forecast Discussion
National Weather Service Louisville KY
1149 PM EST Sat Dec 9 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 940 PM EST Sat Dec 9 2017

Snow showers now have ended, though satellite still shows a weak
plume from Lake Michigan drifting into Scott/Jefferson counties in
Indiana. Upstream obs are not show much in the way of impactful snow
coming out of this band, if any at all. Will update the forecast
shortly to remove evening wording for most spots. Main problem
remains the icy roads from earlier snowfall. Will continue to
highlight the slick roads in a special weather statement that likely
will continue through daylight when sunlight/daytime heating should
correct the issue.

Issued at 725 PM EST Sat Dec 9 2017

Latest satellite imagery indicates the coldest cloud tops now are
only over our Bluegrass and Lake Cumberland counties, and trend in
time is for those colder clouds to be out of here in the next hour
or two. Heaviest band this hour is right along the back edge of
those cold cloud tops, nearing the Harrodsburg/Nicholasville

Another band of snow showers along the IN/OH border also
shows warming cloud tops and a decaying structure on radar. Thus
will taper off snow showers over the next couple of hours and turn
the focus towards slick roads where temperatures dropping into the
lower 20s overnight will cause some driving issues...especially on
any untreated roadways. Have a special weather statement out in two
segments, one where the snow continues and the other where it has
ended to talk about these driving hazards.


.Short Term...(Tonight through Sunday night)
Issued at 310 PM EST Sat Dec 9 2017

...Light Dusting of Snow Possible Through This Evening...

The first wave of light synoptic snow and flurries was pushing east
of the Bluegrass this afternoon, with a second wave of very light
snow/flurries spreading southeast from Indiana. Small pockets of
slightly heavier (but still light) snow were noted near Bloomington
IN on regional radar. Temperatures were hovering on either side of
30 degrees. Thus far today, impacts have been fairly minimal. Many
areas have seen a dusting, with roads briefly becoming lightly
coated in more persistent snow.

The mid-level shortwave trough was centered over Indiana and
Kentucky this afternoon, with a weak surface low near the
Michigan/Indiana border. Surface winds have veered westerly and will
continue to be breezy. Gusts in the 20-30 mph range are likely
through the rest of the day. Colder air wrapping in behind the
system will steepen low-level lapse rates over the next 2-3 hours.
With the DGZ remaining saturated or partially saturated across the
northern and northeast portions of the forecast area, scattered snow
showers spreading in from the northwest may be able to blossom in
coverage/intensity slightly. The area along and north of a line from
Orange Co IN over to Lincoln Co KY has the best chance at seeing
additional light accumulations through this evening. These are the
areas that hold on to more mid-level moisture, and low-level lapse
rates will be near or exceeding 7 degrees C/km. Scattered snow
showers should take on more of a shallow convective nature. These
may produce a very quick dusting this afternoon and evening. Snow
will stick to the roads more readily as we lose insolation.
Narrow/localized pockets of up to a 1/2 inch are possible, but
accums will be highly variable. Most will receive a dusting or less.

Low-level clouds will slowly scatter out from west to east tonight,
and westerly winds will remain somewhat elevated. Therefore, only
went with lows in the low 20s. Warm advection returns on Sunday with
partly cloudy skies expected. Afternoon highs will generally be in
the upper 30s to low 40s.

Warm advection continues Sunday night into Monday in advance of
another clipper diving southeast into the Midwest. Dry weather will
continue through this period, and highs on Monday will reach the 45-
52 degree range. The bulk of the moisture with this system looks to
stay north of the forecast area. However, strong cold air advection
behind the system Monday night could result in flurries or very
light snow. There is an uptick in low-level moisture late Monday
night heading into Tuesday morning. At this time, impacts are
unlikely. Lows will be around 30.


.Long Term...(Monday through Saturday)
Issued at 245 PM EST Sat Dec 9 2017

Tuesday - Wednesday...

A strong cold front will swing through the region Mon night into Tue
morning bringing a robust surge of cold air.  While the model blend
is giving dry or only low POPs, think that some light wintry precip
may be possible with this front or just behind it in strong CAA.  So
added flurries for Tues morning in addition to the 20% POP over east
central KY.  Precip should be in the form of light snow on Tues
although little to no accums are expected at this time.

Behind this front, high temps will be limited to the 30s both
Tues/Wed with night time lows in the upper teens and twenties.

Wednesday Night - Saturday...

A series of upper level shortwaves looks to rotate through the
region Wed night through Thu night providing more chances for a
light snow or flurries during the overnight hours and a mix of rain
and snow during the day on Thu.  Temps are expected to reach the 40s
in most locations Thu.  Long range models are still showing quite a
bit of variability with these weaker waves so confidence is still
low on timing and precip placement.

A dry and quiet end of the week is expected with temps moderating
closer to normal by Sat.


.Aviation...(06Z TAF Issuance)
Issued at 1148 PM EST Sat Dec 9 2017

The pre-dawn hours should be uneventful weatherwise with mostly
clear skies (once the clouds clear out at LEX) and west winds

During the daylight hours a cold front will advance from the upper
Mississippi Valley to the Ohio Valley, with brisk southwest winds
ahead of it. Gusts will top 20kt by afternoon, and may reach 25kt at
times, especially at HNB. Not much else is expected with the front
other than an increase in high clouds.

The front will weaken significantly during the evening hours and
winds will lose their gustiness, becoming light after midnight.




Short Term...EBW
Long Term...AMS
Aviation...13 is the U.S. government's official web portal to all federal, state and local government web resources and services.