Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 221930
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
330 PM EDT Sun Apr 22 2018

.Short Term...(This evening through Monday night)
Issued at 314 PM EDT Sun Apr 22 2018

The first round of rain is slowly moving into parts of south central
Kentucky this afternoon ahead of a fairly large upper level low
(ULL) currently in Arkansas. Forecast models suggest this band of
precipitation will weaken and slow down as it moves northward across
central Kentucky late this afternoon. Another surge of moisture and
rain will quickly move in behind the first round this evening as the
ULL moves steadily toward Kentucky.

Forcing and lift will be supportive of widespread showers with this
second round of rain tonight, and a +50kt LLJ will aid in
transporting moisture northward. It may not be until after midnight
that parts of northern Kentucky and southern Indiana see any rain,
and the trend as of late has been to slow things down. Plan on
having PoPs start for northeastern areas of the CWA just before
sunrise Monday morning.

Drier air wrapping into the ULL will allow for some breaks in the
rain starting Monday morning across south central Kentucky, and
eventually spreading northward Monday afternoon. Models vary quite a
bit on how much of a break we will see, and if there will be any
clearing. With the ULL closing in on southwestern portions of the
CWA Monday afternoon, colder air aloft will allow for some
steepening of lapse rates. In areas that see clearing and a bit of
sunshine, instability could develop. The NAM/GFS show anywhere from
200-300J/KG to 1500J/KG tomorrow afternoon near the BWG area, though
the higher amounts seem a bit overdone. Deep layer shear is nothing
to brag about (0-6km ~25kts), so the threat for severe weather
should remain very low should any instability be realized. With cool
temperatures aloft, we could see some small hail fall in some of the
stronger thunderstorms that develop. Should storms form along
mesoscale boundaries, isolated cold air funnels can`t be ruled out
as well.

Showers will linger through tomorrow night as the ULL moves into
central Kentucky. Best chances for rain will be across the Kentucky
Bluegrass where the best forcing and lift are projected ahead of the
ULL. Temperatures will remain mild, generally in the 50s.

&&

.Long Term...(Tuesday through Sunday)
Issued at 326 PM EDT Sun Apr 22 2018

The upper level low will continue its slow journey to the northeast
on Tuesday. The NAM/GFS indicate some clearing may occur across
parts of the Kentucky Bluegrass and Lake Cumberland region Tuesday
afternoon, resulting in some instability developing. Similar to
Monday, not expecting any severe weather due to weak wind shear, but
could see some small hail in stronger storms due to cold
temperatures aloft.

What`s left of the upper level low will get picked up and absorbed
into an approaching trough on Wednesday. We should see a brief
period of dry weather before another approaching trough/surface cold
front moves in from the northwest sometime Thursday night or Friday.
The model timing differences continue, so will keep PoPs low until
there`s better agreement. By the time we get into the weekend,
surface high pressure will begin settling over the Southeast. A
rather large upper level ridge could establish itself over the
eastern third of the country by the end of the weekend, and could
lead to a period of prolonged warm temperatures and mostly dry
conditions.

&&

.Aviation...(18Z TAF Issuance)
Issued at 105 PM EDT Sun Apr 22 2018

Meandering low pressure near MEM will be responsible for gradually
increasing coverage of rain and lowering of ceilings over the course
of this TAF period. Though brief MVFR vsbys will be possible at BWG
this afternoon in the heavier showers, VFR conditions should prevail
today and this evening, with ceilings falling into MVFR tonight at
BWG and by morning at the other sites as moisture increases.

Winds will come in from the east and will stay up overnight.
Speedier winds aloft around the east and north sides of the low may
create weak LLWS conditions during the overnight/early morning hours.

&&

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

$$

Short Term...DM
Long Term...DM
Aviation...13


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