Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 120523
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1223 AM EST FRI FEB 12 2016

...Updated Aviation Discussion...

...Forecast Update...
Updated at 930 PM EST Thu Feb 11 2016

There are some light returns showing up on radar this evening, but
this is mainly virga at this time, working to saturate the
atmosphere. The latest guidance continues to suggest a band of light
accumulating snow will move in between 09-10Z across south central
Kentucky and drop a quick half an inch to an inch of snow through
mid day. The latest guidance including the NAM/HRRR/local WRF has
shifted a bit further to the south with the band of snow. In
addition, it is suggesting slightly more QPF further to the
southwest as well. Therefore, Logan and Simpson counties were added
in to the Winter Weather Advisory.

.SHORT TERM (Now through Friday Night)...
Issued at 318 PM EST Thu Feb 11 2016

Temps are in the upper 20s to low and mid 30s across the region,
however will quickly fall back into the 20s this evening. As this
occurs, left exit region of an upper jet will slide into the
Tennessee/Green/Cumberland River Valleys, along with deeper
moisture. Latest data has shifted well to the SW with the "heaviest"
axis of snowfall overnight and focuses on the southern two or three
tiers of counties underneath the left exit region. Data shows a 2-4
hour period of good lift with saturation up through the DGZ which
would result in light to briefly moderate snow around sunrise. With
snow ratios nearing 15 to 1, expecting that snow accums could range
between a half inch and 1 inch. Will go with an impact based Winter
Weather Advisory around the morning commute across our south, in
coordination with PAH/OHX/JKL. Amounts won`t be overly impressive,
but slick spots during the morning commute are expected.

Further north, will issue an SPS where flurries and light snow will
have a harder time overcoming the drier air to the north. In this
area, a dusting to a half an inch is possible. A few slick spots
will be possible for the morning commute in these area, but not to
the extent expected further south.

After a brief lull in the late morning and early afternoon, expect
scattered snow showers to commence once again mainly across the Blue
Grass and Lake Cumberland regions. This will mainly be due to
steepening low level lapse rates and a slight upslope component
given NW surface winds. These showers should be light as moisture
will not be as deep by this time. Temperatures will top out in the
30s.

Lows Friday night drop into 10 to 15 degree range. A few upper
single digits are possible. Flurries taper off early in the evening.

.LONG TERM (Saturday through Thursday)...
Issued at 315 PM EST Thu Feb 11 2016

Saturday and Saturday Night

Tranquil period here as high pressure builds in from the northwest.
Question mark as far as how cold it gets Saturday night will be
thicker cirrus building in from the west through the night. Have
gone close to statistical guidance for lows, with readings around
10, but colder in our Bluegrass.

Sunday - Sunday Night...

Light snow accumulations are still looking likely for the Sunday
into Sunday night period. Temperatures will start off in the single
digits to lower teens in the morning, however should warm to the
upper 20s and lower 30s by afternoon. Meanwhile, atmospheric column
will saturate deeper moisture moves into the area ahead a
disturbance over the Great Lakes. Light snow is expected to
overspread the area into the late afternoon and evening, continuing
into the overnight. Right now accumulations look to stay in the 1 to
3 inch range with this system.

Monday - Monday Night...

Focus continues to be on the early week storm system as upper
pattern becomes amplified over the central CONUS in response to a
strong polar jet diving into the northern Plains. Models continue
have trouble the complexity of the upper air pattern and potential
interaction with the subtropical jet. Depending on this interaction
and the eventual strength track of the associated surface low, a
snow or rain scenario is still on the table for our CWA. Most likely
scenario at this point is snow monday morning, changing to a mix or
rain through the day as the warm nose lifts north. Locations across
our northern CWA would be most likely to stay in snow longer, with
our southern CWA more likely to change over. Have reflected this
approach in the latest forecast, but will not take the possibility
of a significant snow off the table until data becomes more
consistent.

As the system departs to the east on Monday night, expect a change
over back to snow as colder air comes back in. Winds would be quite
gusty by this time.

Tuesday - Thursday...

Lower confidence as we head into mid week. There is a signal for
another weak clipper two moving through the NW flow. A few rain or
snow showers are possible with these depending on what time of day
they arrive. Overall, we will see a trend toward milder. Heights
really begin to rise by Thursday as upper ridge gets established
over the central CONUS. Highs could solidly be in the 50s by then.

&&

.AVIATION (06Z TAF Update)...
Updated at 1220 AM EST Fri Feb 12 2016

A clipper system will track through Kentucky over the course of this
TAF period. A band of light snow is likely to impact BWG between 10
and 14z with MVFR to possibly IFR conditions. Snow accumulations of
1 inch or less are expected. Meanwhile, both SDF and LEX is likely
to have flurries or very light snow showers with little aviation
impact. Ceilings will drop down into MVFR, especially under any
particular snow shower or streak at all TAF sites this morning but
the greatest confidence for restrictions is at BWG.

For this afternoon, as the Arctic front comes in, scattered snow
showers are possible at SDF/LEX. These may bring brief periods of
reduced visibility and lower ceilings, but will be short-lived at
any given time. The most likely time frame would be 21-02z.

Winds will also become gusty during the afternoon in advance and
behind the frontal passage. Gusts to 20 kts or so are expected out
of the west.

&&

.LMK Watches/Warnings/Advisories...
KY...Winter Weather Advisory from 5 AM EST /4 AM CST/ to 11 AM EST
     /10 AM CST/ this morning for KYZ026-027-061>067-070>078-081-
     082.

IN...NONE.
&&

$$

Update.........EER
Short Term.....BJS
Long Term......BJS
Aviation.......ZT


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