Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 091742
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1242 PM EST TUE FEB 9 2016

...Updated Aviation Discussion...

...Forecast Update...
Updated at 1129 AM EST Tue Feb 9 2016

Forecast is on track late this morning, and no changes are planned
at this point. Latest radar continues to show light snow across our
area. Visibilities are mostly above 6 miles, so expect very little
additional accumulation is occurring for now. Will keep scattered
coverage wording in through mid afternoon since snow is still
falling, even though it might not be measuring.

Still expect an uptick in coverage/intensity later this afternoon
and into the evening hours ahead of yet another vort lobe rotating
through the parent trough. Temperatures will also increase into the
middle and upper 20s which will help to steepen low level lapse
rates. Visible satellite shows a pretty persistent deck of stratus
over the entire region, however if a few breaks in the clouds are
able to occur that would help showers become a bit more convective.
Additional accumulations of an inch or less are possible through
late this evening, and no changes to the ongoing Winter Weather
Advisory are planned at this time.

.SHORT TERM (Now through Wednesday)...
Issued at 300 AM EST Tue Feb 9 2016

...Snow Covered and Slick Roads Through Wednesday Morning...

The main forecast concern in the short term is snow shower chances,
timing and impacts.

As of 3 am, water vapor and 500 mb heights showed a closed upper low
over northwest Ohio with several embedded shortwaves pivoting across
the lower Great Lakes and Ohio Valley. Regional radar indicated
widespread snow showers across the entire area with embedded
moderate bands at times. Surface observations show visibilities
dropping as low as 1 mile occasionally so bursts of moderate to
heavier snow have been occurring. Temperatures have fallen into the
teens to lower 20s, as a result any residual moisture and melting
snow from yesterday has frozen, creating a thin layer of ice
underneath the fresh, fluffier snow.

Accumulations have been around 1 inch with some locally higher
amounts likely. Reports received since late last evening and early
this morning indicate that untreated surfaces, bridges, overpasses
and side roads are slick and snow covered. As a result, this
morning`s commute will likely have disruptions and delays with
hazardous travel.

Hi-res models are in good agreement that one upper shortwave will
pivot east of the area early this morning, giving way to a relative
lull in activity early this morning. The snow shower activity may
not completely shut off, but for a period it will be lighter or more
isolated. The next wave drops in by early afternoon, coming in
during peak heating, so an uptick in intensity and coverage across
most of the area is expected. This should linger through the late
evening into the overnight hours as well. Through tonight, plan on
an additional 0.5 to 1.0 inch of snow which will keep roads slick
and snow covered.

As a result, the Winter Weather Advisory was extended in time to 10
am EST / 9 am CST Wednesday for the whole area. Snow covered and
hazardous roads will remain possible through the Wednesday morning
commute.

.LONG TERM (Wednesday Night through Monday)...
Issued at 302 AM EST Tue Feb 9 2016

The main weather highlight in the long term period is on the
prolonged winter setup across the lower Ohio Valley, featuring a
parade of upper level shortwaves coming out of Canada along with
unseasonably cold air.

The first clipper in the long term arrives Wednesday night into
Thursday morning. The 09.00z deterministic and ensemble guidance
lacks consistency on timing and placement as the ECMWF is a
faster/southern solution, while the GEM/GFS solutions are further
north and a bit slower. Overall, the southwest/southern forecast
area seems favored for at least a chance of light snow, so have
trended higher snow chances in that direction, but have included at
least flurries for the entire forecast area. Wednesday is still on
track to be the coldest day of the week with highs struggling to
break 20 in places. Add in a stiff west/northwest wind, and wind
chill values are likely to only peak at 10 above during the
afternoon.

Thursday remains on track to be a dry but cold day with highs in the
mid 20s to near 30. Some breaks in the cloud cover are possible by
the afternoon.

A potentially stronger clipper looks to drop in Friday or Friday
night, but again timing/placement details are far from certain. The
09.00z guidance came in with less QPF compared to previous runs and
also further north. But for now, have kept 20 to 30 percent chances
for most of the area.

Both of these clippers would feature low QPF but high snow ratios,
so some light fluffy snow will be possible. Too early to pinpoint if
it will be anything more than just minor accumulations.

In the wake of that system, very cold air spills into the lower Ohio
Valley. Temperature anomalies off the GEFS range from 2 to 3 below
normal so highs this weekend are likely to be in the 20s with lows
in the teens to single digits possible.

Model differences increase quite a bit late in the weekend through
early next week in regard to a potential weather system across the
central Plains and lower Ohio Valley. Lack of consistency between
models and forecast cycles lends toward going with a model consensus
at this time. For now, will advertise chances of snow and/or rain
depending on temperatures.

&&

.AVIATION (18Z TAF Update)...
Updated at 1240 PM EST Tue Feb 9 2016

Have a general light snow across the region this hour, with
scattered to numerous light to occasionally moderate showers
forecast from mid afternoon into the evening hours. Have stayed
optimistic in this package for cigs/vsby, but cannot ruleout briefly
going to IFR for either. Winds will continue from the west, causing
some runway issues at SDF, with some gusts in the 15-20 knot range
this afternoon and evening. The chance for snow will decrease
through the night and Wednesday morning as deeper moisture leaves
the region.

&&

.LMK Watches/Warnings/Advisories...
KY...Winter Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
     KYZ023>043-045>049-053>057-061>067-070>078-081-082.

IN...Winter Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for
     INZ076>079-083-084-089>092.

&&

$$

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


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