Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211054

654 AM EDT Tue Oct 21 2014

...Updated Aviation Discussion...

.SHORT TERM (Now through Wednesday)...
Issued at 305 AM EDT Tue Oct 21 2014

Cold front is progressing slowly through the Ohio Valley overnight,
with surface winds still out of the WSW over nearly the entire state
of Kentucky. Decent strato-cu shield is evident over the northern
half of Indiana and much of Ohio as the low levels are modified by
Lake Michigan.

As the day progresses, the front will push SE across the region, and
deep NNW flow will develop. Most of the column will be quite dry,
but the fetch off of Lake Michigan will draw a shallow ribbon of
moisture into southeastern Indiana and the Bluegrass region of
Kentucky. Will include a brief window late this morning for a
shallow light shower or two to develop, but both coverage and QPF
will be minimal. Clouds and cold advection will really hold temps
back, and we can expect a decent range from NE to SW. Most of the
Bluegrass region will struggle to crack 60, while south central KY
will be up to 10 degrees warmer.

Expect clearing skies tonight and plenty of sunshine on Wednesday as
the surface ridge builds from the NW while the upper ridge builds
from the SW. Light north winds overnight will keep temps from
bottoming out, so will favor the slightly milder NAM MOS for lows
tonight. Wednesday will run even cooler with the shallow cold air
mass tightening its hold, with upper 50s across the board.

.LONG TERM (Wednesday Night through Monday)...
Issued at 255 AM EDT Tue Oct 21 2014

In contrast to the last few days of multiple frontal passages, the
long term pattern will settle down, with little if any rain chances
and temperatures starting off near normal then steadily rising. The
GFS does have a weak front passing us Thursday night and Friday. As
with the last few systems, models fade precip chances away before
getting here, but wonder if we will be able to squeeze out a
hundredth of an inch in a few spots. The latest SREF hints at this
chances, and will trend up just a little in pops, but stay under 20
percent. That front will slow the rise in temps for one day, but
Saturday and Sunday ridging will build into the region. On Monday
southerly winds will pick up ahead of a cold front across the
Central Plains. This front will hold off getting in here until just
beyond this forecast period.

The only other thing to mention in this forecast is the chance for
frost Thursday morning. Most of the model guidance places the center
of a surface high near our region by daybreak.  Forecast lows should
be in the 30s areawide, with our Bluegrass counties at least
dropping into the mid 30s. Thus expect at least areas of frost there
with patchy frost farther west. Would not be surprised to see the
next couple of forecasts come in a little cooler, with a frost
advisory possible for portions of our forecast area.


.AVIATION (12Z TAF Update)...
Updated at 645 AM EDT Tue Oct 21 2014

Cold front slowly making its way SE across Kentucky is quite
difficult to pick out in the surface obs. Strato-cu deck ihas pushed
into LEX and will soon get into SDF, but higher than previously
advertised and will stay solidly VFR. Main challenge this morning
will be how long the fog stays in BWG.

Even high-resolution guidance has struggled to catch on to the fog
at BWG. Will fall back on a bit of climo in keeping restrictions to
vis through 14-15Z, but will be a last-minute call as to just how
poor visibility will be. First guess would be prevailing IFR/MVFR
with TEMPO for vis dropping to field mins.

Once the fog dissipates at BWG expect VFR through the day, but will
keep a strato-cu ceiling in SDF and LEX. Winds will be NNW behind
the front, but the cold advection push is weak enough that speeds
will hold just under 10 kt. Skies will clear and winds will decouple
after sunset. Cooler and drier air will continue to filter in, but
drying will be just slow enough that we will keep a TEMPO for IFR
visibility at BWG toward daybreak Wednesday.




Short Term........RAS
Long Term.........RJS
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