Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 201218

Area Forecast Discussion
National Weather Service Louisville KY
818 AM EDT Fri Sep 20 2019

.Forecast Update...
Issued at 817 AM EDT Fri Sep 20 2019

Seeing isolated coverage of showers and even 1 decent thunderstorm
over the past few hours as a weak LLJ created just enough moisture
transport in the presence of 500-1000 J/KG of MU CAPE. This sparked
the isolated activity, but expect it to weaken/diminish by mid to
late morning as the LLJ is lost. Updated the grids to include pops
all the way to the TN border where there is some activity down down

Issued at 540 AM EDT Fri Sep 20 2019

Within the last hour, a few sprinkles have blossomed into actual
showers along the Ohio River. Have updated PoPs to mention isolated
showers through mid-morning but actual coverage will likely be 10
percent or less.

Issued at 445 AM EDT Fri Sep 20 2019

Seeing a few short-lived radar returns, as well as a few drops on
the windshields here at the NWS office. Not expecting anything more
than these few high-based sprinkles, and anything that does measure
will be less than 10 percent coverage. Therefore a quick update has
gone out to mention sprinkles this morning without a change to POPs.
The streak of days without measurable precip should remain intact at
24 or 25 for most of the area.


.Short Term...(Today and tonight)
Updated at 315 AM EDT Fri Sep 20 2019

Current satellite and radar imagery show quiet conditions across the
region. A few high-res models are hinting that short lived isolated
showers could begin developing before sunrise along the nose of a
very weak LLJ, however, not thinking we will see much in the way of
precip at this time. Primarily since the limited moisture around 5-
6KFt found in most model soundings is outweighed by the overall
dryness of the boundary layer. Instead, thinking increased cloud
cover will be the more likely scenario with a few sprinkles
possible. Have decided to keep PoP wording out of the forecast for
those reasons mentioned above coupled with the drought conditions we
have been experiencing lately.

As we head into mid-morning, winds will gradually increase, with
gustier winds likely west of I-65. Increased cloud cover this
morning could limit temperatures from rising initially, however, it
does appear that by mid morning we will mix enough dry air to result
in mostly clear skies. As a result, have afternoon highs climbing
into the mid to upper 80s.

.Long Term...(Saturday through Thursday)
Updated at 255 AM EDT Fri Sep 20 2019

Hot ridge over the eastern CONUS remains in control through the
weekend, with temps pushing 90 each day. This is actually near or
even just above the ECMWF, which is the warmest guidance.

Progressive upper trof will push through the Great Lakes Sunday
night and Monday, bringing the first decent chance of rain in nearly
a month for most of the Ohio Valley. Even so, with the upper support
leaving the front behind, the precip will be breaking up as it
pushes south and east. Therefore POPs will taper from 60% Sunday
night over southern Indiana, to just 20-30% on Monday across parts
of south-central Kentucky. For QPF we will lean on the WPC solution,
which is about half of the model consensus. Hardly a drought-buster
with a half inch over southern Indiana being the best case for
a basin average.

A bubble of high pressure Monday night and Tuesday will bring
briefly seasonable weather to follow the autumnal equinox. A
relatively flat upper pattern will prevail for much of the week as a
closed low digs into the Desert Southwest. Expect mainly dry weather
in the Ohio Valley, aside from the odd slight chance for southern
Indiana as weak disturbances pass by to our north and west. Temps
Wed-Fri will run solidly above normal, but will be cooler than this


.Aviation...(12Z TAF Issuance)
Updated at 645 AM EDT Fri Sep 20 2019

VFR conditions are expected through this TAF period. Current radar
imagery does show a few isolated showers along the Ohio River,
however, these will be short lived and are not expected to impact
any of the TAF sites at this time. Latest obs show mid level
ceilings have already begun affecting BWG/SDF/LEX and will continue
to do so through most of the morning. Gusty southerly winds will
help to mix out the boundary layer and lessen cloud cover by mid-
afternoon. Otherwise, winds are expected to back southeasterly and
become light shortly after sunset.




Short Term...SSC
Long Term...RAS
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