Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 181746

Area Forecast Discussion
National Weather Service Louisville KY
146 PM EDT Fri May 18 2018

...Updated Aviation Discussion...

.Forecast Update...
Issued at 1054 AM EDT Thu May 17 2018

Forecast is on track for an increase in shower and storm coverage as
we move into the afternoon. A weakly defined warm front extending
from the low pressure over western TN is expected to lift north
today, with scattered to numerous showers and storms near the
boundary. Seeing some clear spots on satellite imagery to our south,
so pockets of moderate instability should be able to develop.
Overall, forecast soundings support the threat of efficient rainers
given the tall/skinny CAPE profile coincident with precipitable
water values around 1.7 inches through the column. One thing
different from yesterday is that these storms should have some
better motion, and won`t sit over one area for too long. Still,
we`ll have to keep an eye on areas that get repeated rainfall. No
updates planned to the ongoing products at this point.


.Short Term...(Today and tonight)
Issued at 310 AM EDT Fri May 18 2018

It`s another warm, muggy night with temperatures ranging from the
mid 60s to low 70s. Still getting a steady 5-10 mph wind out of the
northeast across much of the area, with light and variable flow in
southern KY. That`s closer to a weak sfc boundary draped across
Middle Tennessee. Weak surface low pressure was analyzed over
northern MS this morning.

Fog hasn`t been an issue thus far, thanks to more BL wind and plenty
of mid and high cloud cover. However, models continue to hint at low
stratus forming between 10-16z before lifting this afternoon. At the
sfc, weak warm front will lift north through the area today and
tonight. An upper level trough will continue to propagate northeast
over the lower Ohio Valley as well. Plenty of cloud cover should
keep temperatures just a touch cooler than yesterday, with highs in
the mid 70s to lower 80s.

As for rain, just have subtle, scattered sprinkles sliding
northwest on radar currently. We may see a more bona fide area of
light rain move into the eastern CWA from the southeast toward
12z. Activity should stay isolated to widely scattered this
morning, with perhaps a rumble of thunder by 15z. But expect more
convective development starting around 18z, with scattered
thunderstorms through the evening hours. Motion of this activity
will be to the NNW today. Locally heavy rainfall and ponding of
water certainly looks possible once again. Flash flooding would
only be a threat where cells train over the same area.

Winds veer southerly tonight as low pressure continues to lift north
of the area. Precip coverage will decrease, but scattered showers
and a few storms are possible. Lows will be in the mid to upper 60s.

.Long Term...(Saturday through Thursday)
Issued at 300 AM EDT Fri May 18 2018

Unsettled pattern will mean a continuation of June-like temps and
mainly diurnally driven shower/thunderstorm chances through at least
Tuesday. Air mass will be quite moist with precipitable water values
near or above 1.5 inches, and there is enough instability to support
a few pulse storms, but mid-level flow is too weak for any

Will finally start to trend POPs downward a bit Wed-Thu as a trof
digs into the Canadian maritimes and sets up a NW flow regime, but
confidence is quite low as to whether the quasi-stationary front can
be displaced far enough to give us any sustained dry weather.


.Aviation...(18Z TAF Issuance)
Issued at 146 PM EDT Fri May 18 2018

A weak, but moisture laden low pressure system will pivot through
the area this afternoon and tonight. Then, a stronger disturbance
will rotate through on Saturday. These features will provide the
focus for rounds of showers and thunderstorms through this TAF
cycle. In addition, ceilings will likely range from fuel-alternate
MVFR up through VFR at times. Visibilities are expected to stay VFR
outside of any shower or storm, where brief IFR visibilities are

The best timing for afternoon/evening showers and storms will be
from now until 6 or 7 PM tonight. Will keep VCSH in for much of the
night, then another round of showers and storms is expected late in
the TAF period on Saturday. The best timing for low ceilings will be
the few hours on either side of dawn on Saturday.




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