Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 232308

Area Forecast Discussion
National Weather Service Louisville KY
708 PM EDT Sun Apr 23 2017

...Updated Aviation Discussion...

.Short Term (Now through Monday Night)...
Issued at 220 PM EDT Sun Apr 23 2017

Surface analysis reveals a 1008mb low over northwestern Georgia with
a cold front draped down into the Gulf of Mexico. A look upstairs
near 500mb reveals a low close to the TN/AL/MS border. Visible
satellite loops show a nice "swirl" in the clouds over the lower
Tennessee valley associated with the system.

In our neck of the woods, persistent clouds and precipitation
associated with wrap-around moisture from the upper level low have
resulted in a soggy Sunday for south-central Kentucky. North-central
Kentucky and southern Indiana have remained mostly dry thanks to
drier air advecting into the lower levels of the atmosphere, but mid
to high level clouds have blocked out the sun for most folks.

We should see the system and its precipitation shield gradually dig
into the southeastern US this afternoon and evening. This will allow
some clearing and drying generally from northwest to southeast. Most
folks should be rain free by Monday morning. The cloud forecast, on
the other hand, looks to be a bit more complicated. While the models
show some clearing in southern Indiana and north-central Kentucky
late this afternoon and evening, it appears some low to mid level
moisture will advect back into the area Monday morning and keep the
region mostly cloudy by Monday afternoon. Like today, the gradient
between clouds/clear skies will be sharp on Monday and will have an
impact on the high temperatures.

Clouds could still linger into Monday night, but should start to see
them dissipate by sunrise Tuesday morning. Lows will generally be
mild in the low 50s.

.Long Term (Tuesday through Sunday)...
Issued at 230 PM EDT Sun Apr 23 2017

Upper level ridging will continue Tuesday and Wednesday, bringing
warm temperatures and dry conditions to southern Indiana and central
Kentucky. Latest 12z guidance still shows cold frontal passage
overnight Wednesday into Thursday morning, with a line of showers
and thunderstorms ahead of the cold front. As previous discussions
have mentioned, a lack of instability should keep thunderstorms
ahead of the cold front sub-severe, despite modest low level
moisture and shear profiles. Showers and thunderstorms could linger
through Thursday morning into the early afternoon.

Cool-down from cold front will be short lived, as a warm front is
progged to move through and north of the region Friday. Long range
models show a broad band of showers and thunderstorms associated
with the warm frontal passage continuing through Saturday morning.

Despite some minor differences, long range models are in decent
agreement to keep a good portion of the weekend mostly dry, but very
warm, with some models showing high temperatures near 90 degrees.
Won`t go quite that warm in the grids with temperatures, but do
expect above normal temperatures as well as isolated to scattered
thunderstorms during this period.


.Aviation (00Z TAF Update)...
Issued at 655 PM EDT Sun Apr 23 2017

Slow-moving upper low will continue to dive into the Deep South
through the valid TAF period. This system continues to sling
moisture westward into east-central and south-central Kentucky,
keeping BWG and LEX in MVFR ceilings, as well as rain that has been
slow to release its grip in BWG. Forecast confidence is limited as
we will remain near the NW edge of an otherwise persistent cloud
shield, with the potential to either build down or clear out.

Will be a last-minute decision whether BWG will be initialized in
fuel-alternate, as it is currently high-end MVFR like LEX, but lower
ceilings are lurking in the developing gap between the upper low and
its main moisture feed. GFS LAMP guidance is keeping fuel-alternate
ceilings in, but it has been too pessimistic recently and other
short-term guidance suggests a low probability of even fuel-
alternate. Will have BWG recovering to high-end MVFR, and LEX to VFR
if it isn`t already, but can`t rule out a build-down given the
residual low-level moisture.

Will keep SDF in VFR, with the stratus scattering out toward
daybreak. However, another stratus deck could develop and/or
pinwheel in Monday afternoon. Will bring it in as a ceiling but keep
it VFR. Will keep NE winds around 10 kt across the board.




Short Term........DM
Long Term.........DM
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