Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 221052
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
652 AM EDT Sat Apr 22 2017

...Updated Aviation Discussion...

.Short Term (Now through Sunday Night)...
Issued at 257 AM EDT Sat Apr 22 2017

The main forecast challenge in the short term is precipitation
timing and rainfall amounts through this evening.

As of early this morning, a surface analysis showed a stationary
front across middle Tennessee into far eastern Kentucky. Generally
north to northeast winds prevailed across southern Indiana and
central Kentucky with temperatures steady in the upper 40s to middle
50s. In the last 6-8 hours, a couple waves of showers have spread
across the region. MRMS precipitation estimates show generally
around 1/2 inch has fallen along and north of the Ohio River while
slightly heavier amounts, upwards to an inch, fell along the KY/TN
border. In between, amounts have been mainly under 1/10 of an inch.

Regional radar shows another area of widespread showers and embedded
thunderstorms tracking across southern Missouri and northern
Arkansas. This is well represented in the hi-res, near-term model
guidance, and it will advance eastward toward our area, reaching
central Kentucky around sunrise. Expect widespread rain with some
embedded thunder for period of 3-6 hours, before tapering off to
spotty showers west to east late in the morning. Another wave of
showers is possible again early this afternoon, as depicted by the
latest runs of the HRRR and RAP, through mid to late afternoon,
however coverage and intensity of this wave may be less compared to
this morning.

There is increasing consensus that showers and storms will push or
stay further south along the TN border and/or across southeastern
Kentucky for the late afternoon and evening hours, closer to the
surface low that will be tracking across Tennessee. Areas along and
north of the Ohio River may see just isolated showers or end up dry.
As a result, trended precipitation chances toward that idea,
lowering into the 20-30% chance range for southern Indiana and
north central Kentucky after about 4-5 pm.

Rainfall amounts through tonight are expected to be on the order of
1 to 1.5 inches, highest amounts across south-central Kentucky. Some
localized heavier amounts are possible, especially along the KY/TN
border areas. While recent antecedent conditions have been dry,
soils have had some priming, especially around the Lake Cumberland
region where 1-hr flash flood guidance is around 1 inch, and 3-hr
values are around 1.5 inches. As a result, will put out a Flash
Flood Watch for that area in effect through Sunday morning with the
expected rounds of rainfall through tonight.

Temperatures today will be noticeably cooler compared to recent days
with highs stuck in the 50s except in the low 60s across south-
central Kentucky. There will be steady northeast wind with some
gusts 20-30 mph at times.

Clouds and isolated to scattered showers will persist across
portions of the area Saturday night but will begin to taper off late
tonight. Clouds will stick around into the first part of Sunday, and
with the upper level low nearby, there`s a continued threat of
showers across south-central Kentucky. Highs in that region will
stay in the 50s while back across southern Indiana, more sun and
drier conditions will help push highs into the mid/upper 60s.

.Long Term (Monday through Saturday)...
Issued at 258 AM EDT Sat Apr 22 2017

Weak upper level ridging will spread across the lower Ohio Valley
Monday and Tuesday while surface high pressure builds in from the
west. This should provide a couple of seasonable, dry days for the
area. Plan on highs in the 70s with cool mornings in the 50s.

The 22.00z guidance remains in good agreement to past cycles showing
the next weather system to approach the area Wednesday afternoon
through Wednesday night before stalling out across Tennessee
Thursday. The deterministic models then advertise this front lifting
back to the north as a warm front, giving way to warmer temperatures
for the end of next week, then potentially unsettled weather for
next weekend.

&&

.Aviation (12Z TAF Update)...
Issued at 652 AM EDT Sat Apr 22 2017

Complicated weather this TAF period as a couple of surface lows pass
by to our south and an upper low advances from eastern Kansas to
western Tennessee.

A couple waves of showers will push through central Kentucky. One is
in the area now, and the second will be moving through during the
early to mid afternoon hours. Will hang on to prevailing MVFR
ceilings, but in reality cloud bases will be quite variable,
occasionally dipping to high-end IFR and briefly rising into low-end
VFR.

Winds will come in from the northeast and may gust into the 20-25kt
range, especially this afternoon.

Conditions should slowly improve this evening, especially at SDF
which will be furthest away from the surface low and its attendant
low cigs/rain. Winds will lose their gustiness, but will remain
brisk from the northeast.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Flash Flood Watch through late tonight for KYZ075-078-081-082.

IN...NONE.
&&

$$

Short Term........ZT
Long Term.........ZT
Aviation..........13



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