Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 191032

Area Forecast Discussion
National Weather Service Louisville KY
632 AM EDT Wed Apr 19 2017

...Updated Aviation Discussion...

.Forecast Update...
Issued at 615 AM EDT Wed Apr 19 2017

Scattered showers and a few embedded T-storms now working their way
over into the Bluegrass as a weak impulse aloft pushes east across
Kentucky. Cloud shield over the Tennessee Valley is getting
suppressed far enough south and east that the deeper moisture needed
for redevelopment of convection will be lacking. Minor tweaks to
grids will trim back the precip chances later today, especially west
of I-65.


.Short Term...(Today through Thursday Night)
Issued at 300 AM EDT Wed Apr 19 2017

Warm and unsettled weather continues under zonal flow aloft and
moist SW flow in the low and mid levels. The juicy air mass makes it
difficult to go completely dry at any point, and within the last
hour we have seen a smattering of showers develop around Mammoth
Cave in central Kentucky.

Expect isolated to scattered showers east of I-65 this morning as
the ongoing activity lifts to the NE. With a bit more sunshine than
the last couple of days across southern Indiana and north-central
Kentucky, there could be enough of a differential heating boundary
to focus scattered convection over south-central Kentucky this
afternoon. Instability will be limited by modest mid-level lapse
rates and wind fields are not impressive, so would not expect any
organized severe wx.

After a mild and dry night, the gradient will tighten ahead of an
approaching cold front on Thursday. Showers and thunderstorms along
or just ahead of the front will arrive in southern Indiana during
the late afternoon, and push SE across central Kentucky during the
evening. Even with decent low-level forcing along the front, the
instability is marginal especially given the later evening arrival
for most of the area. Shear is also modest, so if anything expect a
few strong storms in the line to produce locally gusty winds. SPC
Day 2 Marginal Risk seems to capture this fairly well, with the best
chance for a stronger storm over southern Indiana where convection
is expected to coincide with better heating.

.Long Term...(Friday through Tuesday)
Issued at 300 AM EDT Wed Apr 19 2017

...Unsettled weather to continue through the weekend...

Once the front pushes through Thursday night, expect it to hang up
somewhere near the Kentucky/Tennessee border, where it will linger
through Friday. Look for a cloudy and cool day on Friday, with
scattered showers mainly over south-central Kentucky where moist mid-
level air rides up and over the nearly stationary front.

Still searching for model consistency regarding Saturday, when a
closed upper low works its way across the Central Plains, sending a
surface low somewhere across the Ohio and Tennessee Valleys.
Confidence is increasing in more of a southern track, but the timing
and extent of the precip shield remains a question mark. While the
most persistent and intense rainfall is likely to fall across south
central Kentucky, there is still potential for a soaking rain for
much of Saturday across all of central Kentucky and even into
southern Indiana. A few embedded thunderstorms are also possible,
instability needed for any strong storms is lacking. Temps may
struggle to get out of the 50s across southern Indiana, while south-
central Kentucky could get into the 70s if the warm front is drawn
far enough north. Late Saturday or Saturday night will be a
transition from the soaking rain to light showers or even drizzle
under the cold pool aloft.

Lingering showers possible on Sunday with the upper trof still
hanging back across the Ohio Valley, but should give way to dry
weather for Monday-Tuesday as a new closed low dives into the Deep
South. Temps recover back above climo for the first half of next


.Aviation...(12Z TAF Issuance)
Issued at 630 AM EDT Wed Apr 19 2017

Have opted for a tempo group for possibility of BKN MVFR ceilings
at SDF this morning. Advection of drier air via stout SW flow looks
to keep ceilings more SCT. Slightly better chance for MVFR,
especially through the mid-morning hours, at LEX. An isolated shower
or perhaps a storm remains possible into the early afternoon at LEX.
A heavier shower could briefly lower visibility. BKN deck east of I-
65 is expected to continue to push east and gradually lift toward
midday. Outside of any brief MVFR this morning, conditions will
remain VFR through Thursday morning. Southerly winds will gradually
turn southwesterly from mid to late morning and increase to 8-12




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