Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 280739

339 AM EDT Mon Jul 28 2014

.SHORT TERM (Now through Tuesday)...
Issued at 335 AM EDT Mon Jul 28 2014

Much quieter this morning and this benign weather is expected to
prevail in the short-term period. Persistence in the models calls
for a chance for light rain showers tomorrow, primarily in the
Bluegrass region and southeastern IN, although a stray shower or
some sprinkles could fall elsewhere, with the focus remaining on
locations east of the I-65 corridor. The Ohio Valley will be on the
backside of the trough tomorrow, leaving the region under NW flow at
the surface and aloft. The upper jet will be digging in and a vort
max is expected to rotate through southern IN and central KY,
providing a lifting source. Additionally, steep low-level lapse
rates and PWATs of around an inch will provide scattered to broken
clouds across much of the forecast area. While the PWATs don`t seem
terribly impressive, what is to note is that the bulk of the
moisture is confined to the lower levels. Once diurnal heating is
lost tonight, expect any showers that had developed to wane, along
with some of the cloud cover. By Tuesday, this forecast area will
have lost some of that support and moisture, so currently
anticipating that precip should remain north of the area,
particularly as surface high pressure attempts to take control from
the west.

Unseasonably cool temperatures and much lower dewpoints are already
advecting in behind the fropa. The airmass change of Canadian
origin, along with the cloud cover, will keep highs today from
reaching the 80 degree mark in southern IN and northern KY. Southern
KY will reach right around 80 degrees. Tonight, lows will be in the
mid 50s with assistance from radiational cooling, if the clouds can
clear out enough. Tuesday will be cooler across the south and about
the same for the north, ranging from the mid to upper 70s.

So how do these forecast temperatures compare to records? Well, FFT
looks to be the only climate site today to have the potential to
come close to their min high temperature of 74 degrees, set last
year. For tonight, SDF and possibly LEX could come close to their
record lows of 58 and 54 degrees, respectively. Tuesday could be a
bit more difficult, with FFT being the only one in range of 74
degrees set in 1994 and previous years.

.LONG TERM (Tuesday Night through Sunday)...
Issued at 305 AM EDT Mon Jul 28 2014

At the beginning of the long term period, a highly amplified pattern
will exist with ridging in the western CONUS and troughing in the
east.  We`ll be under the influence of the trough providing for
unseasonably cool temps.  Will keep a dry, mostly sunny forecast for
mid week since most models are still projecting this but it should
be noted that the latest NAM12 run is a little more aggressive
dropping shortwave energy south in the trough and giving light
precip chances over our southern Indiana/northern Kentucky counties
both Wed and Thurs.  Wed morning will be the coolest morning in the
long term period with lows in the 50s over most locations and low
60s in the Louisville Metro.  Valley locations over east central KY
will see temps bottom out in the low 50s even!

For Friday through the weekend, long range models have come into
agreement that the upper trough will narrow and sharpen on its
southern most extent but will not become a closed low over the
Midwest.  On and off scattered rain chances still look on track
Fri-Sun as multiple vort lobes dive south into the Ohio Valley with
the best activity most likely during the afternoon/evening hours
each day.  This activity will start to decrease on Monday as the
upper trough moves east of our area.

Temperatures throughout the long term period look to be pretty
steady state with highs in the upper 70s to mid 80s and lows in the
upper 50s and lower 60s.  Clouds and precip chances may make temp
forecasting a bit more challenging for the weekend.


.AVIATION (06Z TAF Update)...
Issued at 122 AM EDT Mon Jul 28 2014

VFR will be the predominant category through much of this TAF
period, with potentially MVFR at LEX over the next few hours. Winds
are expected to be right around or slightly above 5 knots throughout
the night, despite some decoupling due to much cooler, drier air
advecting in behind the exiting cold front. Just a few passing
clouds can be expected overnight, which, in addition to the CAA,
will allow for plenty of radiational cooling. Bringing this all
together, the reason for the potential of MVFR at LEX is due to
enough surface moisture to allow for a low-level deck to build in
but the winds should stay up just enough to mitigate a more
significant impact. SDF could see some haze by sunrise but isn`t
expected to drop below VFR. BWG did not receive as much rain as the
other two terminals, hindering much more than haze there as well.
However, should the winds settle down over the next couple of hours,
will need to monitor and update as necessary.

For Monday, mostly clear skies will prevail in the morning before a
CU field develops in the afternoon. There is a chance for some light
rain to fall across portions of northern and eastern KY with LEX
having the higher potential of the three terminals, although SDF
can`t rule it out completely. Given the uncertainty, and that the
impacts are expected to remain relatively minimal to aviation
interests, have negated mention in this forecast update.




Short Term........lg
Long Term.........AMS
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