Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211816
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
216 PM EDT Fri Apr 21 2017

.Forecast Update...
Issued at 215 PM EDT Fri Apr 21 2017

Did a quick update to reduce PoP coverage substantially across the
region.  We`re currently in a lull with regards to precipitation.
Clouds have also mixed out a bit and temperatures are gradually
warming up.  So have bumped up highs a bit down across southern
Kentucky.  Temperatures may need to be bumped up a little further in
areas along the Ohio River as well if breaks in the clouds develop.

Issued at 1121 AM EDT Fri Apr 21 2017

Band of weak convection continues to move east-northeast across the
region.  The convection is mainly along and north of the WK and BG
Parkways, with a slightly heavier band just north of the Ohio River.
Last few runs of the HRRR seem to have a decent handle on this
precipitation.  Those runs indicate that this current batch of
rainfall will continue to work eastward into the Bluegrass region of
Kentucky this afternoon with somewhat of a break in the
precipitation for our western and southern areas as we move into the
early afternoon hours.  Looking at radar mosaics from across the
region, this seems reasonable.  The precipitation break will not
last long however, as next convective band out across southern MO
and northern AR moves east-northeast and into the region later this
afternoon.

Strong to severe convection looks very low at this point.  The best
chances of thunderstorms looks to be more focused across Tennessee
this afternoon, though some embedded thunderstorms will be possible
across far southern KY.  Further north across southern IN and
northern KY, weak lapse rates and little if any destabilization due
to clouds and precip look to keep convective chances rather low.

Due to the clouds, we did back off high temperatures somewhat across
southern IN and northern KY.  Highs in this area will likely warm
into the upper 50s to the lower 60s this afternoon.  The warmest
readings of the day will be across southern KY where highs in the
mid-upper 60s look much more likely.  A 70 degree reading here or
there down in the Lake Cumberland region looks attainable as well.

&&

.Short Term (Now through Saturday)...
Issued at 300 AM EDT Fri Apr 21 3017

A cold front passed through Louisville shortly after 06Z and will
continue to head to the south into Tennessee this morning. There was
very little convection associated with this boundary overnight in
southern Indiana and central Kentucky, and only scattered cells are
expected this morning. This afternoon coverage is expected to
increase with diurnal heating, the cold front over the Tennessee
Valley, and the interaction of an upper wave coming in from the west
that assisted in the development of thunderstorms in Oklahoma
overnight. While an elevated storm in southern Kentucky could
produce some small hail this afternoon, the best chance of
strong/severe storms should be over Tennessee.

Tonight rain chances will increase, especially after midnight, as a
surface low advances from Oklahoma into Arkansas ahead of its parent
5H low moving into the Ozarks. That system will continue to push
eastward into the Ohio and Tennessee Valleys on Saturday,
accompanied by widespread rain.

There are several indicators that suggest heavy rain late Friday
night through Saturday. Isentropic lift on the 305K surface will
develop Friday night and strengthen significantly on Saturday,
accompanied by high RH levels...especially south of the Ohio River.
Positive 850 theta-e advection is expected over southern Kentucky on
the nose of an 850 theta-e ridge and jet reaching from the central
Gulf Coast to the Tennessee Valley. CAPE is very weak and soundings
show deep warm cloud depth. However, K Index stays in the low 30s.
Precipitable water values will rise above normal but not to extreme
levels. Soundings show some dry air aloft. Perhaps most
significantly, though, is that antecedent conditions are relatively
dry. We didn`t get as much rain last night as originally expected
and the rivers are not running high. The Lake Cumberland region,
which stands the best chance at the heaviest rain, has only received
50-75% of its normal rainfall over the past seven days. The lowest
tier of Kentucky counties is actually "D0" on the U.S. Drought
Monitor. So, those areas can take some rain, depending on just how
quickly and heavily it falls.

In addition to the wet weather, Saturday will also be fairly chilly.
Highs will only be in the lower and middle 50s in southern Indiana
and north central Kentucky, which is 10 to 15 degrees colder than
normal and much cooler than what we have been experiencing over the
past couple of weeks. On top of that, northeast winds of 10 to 15
mph with gusts of 20 to 25 mph can be expected.

Temperatures in southern Kentucky will be warmer on Saturday, rising
into the lower and middle 60s, along with lighter winds.

.Long Term (Saturday Night through Thursday)...
Issued at 304 AM EDT Fri Apr 21 2017

Behind the departing surface system Saturday night/Sunday showers
will continue as the upper low approaches and moves overhead. Rain
coverage should be more scattered and amounts lighter than what we
experienced on Saturday. Still, by the end of the weekend, totals of
1-2 inches can be expected...possibly more near the Tennessee border.

Monday-Tuesday will be dry with weak ridging at the surface and
aloft.

Wednesday the next front will come in from the northwest accompanied
by showers and a few thunderstorms. The front is expected to make it
into Kentucky Wednesday night then surge back northward on Thursday.

After the cool weekend we will make it back into the 80s by
Wednesday and Thursday.

&&

.Aviation...(18Z TAF Issuance)
Issued at 120 PM EDT Fri Apr 21 2017

Scattered showers ongoing across central Kentucky and southern
Indiana at this hour. Should see shower activity taper down over
the next hour or two and allow a brief break before the next round
of rain and low clouds arrives this evening. Expect MVFR/IFR
ceilings and visibility this evening through much of tomorrow with
the next round of showers. Isolated thunderstorms may also be
possible tonight over BWG but confidence in them occurring is too
low to introduce in forecast at this time.


&&

.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&

$$

Update............MJ
Short Term........13
Long Term.........13
Aviation..........DM



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