Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 240518
AFDLMK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
118 AM EDT Thu Jul 24 2014

...Updated Aviation Discussion...

...Forecast Update...
Issued at 936 PM EDT Wed Jul 23 2014

Scattered to numerous showers and a few storms continue to linger
across the Lake Cumberland region, with very slow movement eastward.
Continue to be concerned about some localized areas that have picked
up a few inches of rainfall with different rounds of storms, however
the overall trend on radar displays weakening. Will gradually
diminish coverage in that region over the next few hours.

A secondary area of very weak showers is also sinking south across
southern Indiana and north central KY ahead of what looks to be the
actual frontal boundary. Will continue to leave mention of an
isolated shower or storm this evening, with isolated showers
associated with this feature overnight. Model time heights and
soundings show a pretty moist 1000-850 mb layer overnight, with an
approaching wave currently over eastern Iowa. Think we could get
some measurable showers or drizzle lingering after Midnight and into
the pre-dawn hours so hold slight chance pops all night.

Think the heavy cloud cover and northerly winds between 5 and 10 mph
should be enough to limit fog production, however cannot rule out
fog in the areas that saw rain today.

Issued at 606 PM EDT Wed Jul 23 2014

Scattered to numerous storms have re-fired ahead of the cool frontal
boundary currently along a BWG/LEX line, with the aid of
differential heating from upper level clouds. These storms are
moving slowly off to the east, and have been able to produce very
heavy rainfall, a localized damaging wind gust and hail. The threat
for stronger storms will diminish over the next two hours as storms
move east of the area, and we lose daytime heating. Did update the
forecast to increase rainfall totals and increase coverage of
t-storms this evening.

.SHORT TERM (Now through Thursday Night)...
Issued at 320 PM EDT Wed Jul 23 2014

The cold front was very near the Ohio River as of 3pm.  Most storms
have exited the region with thinning of clouds noted.  With many
daylight hours left, some instability may rebuild and forcing from
the front could cause a few more storms/showers to redevelop late
this afternoon and evening.  However, the strongest forcing along
the front will remain SW of our region and earlier showers/storms
have created a more stable moist environment.  Post frontal
convection near IND is dissipating as well.  Thus, think that more
showers/storms are possible but will limit POPs to 20-30% for this
evening.  Also, any convection that does form is expected to remain
below severe limits due to limited forcing and instability.  In
fact, it will probably be hard to even get a strong storm going with
gusty winds in this environment.

Any convective activity should cease after midnight with only some
patchy light drizzle/low clouds and maybe even some light fog late
tonight into tomorrow morning.  A cooler airmass will enter the area
resulting in low temps in the 60s tonight.

With sfc high pressure and upper level troughing over the region
Thurs/Thurs night, we`ll experience unseasonably cool conditions.
Highs Thurs afternoon will drop back into the upper 70s and lower
80s with skies becoming mostly sunny during the afternoon hours.
Thurs night lows will bottom out in the upper 50s and lower 60s
under mostly clear skies.

.LONG TERM (Friday through Wednesday)...
Issued at 320 PM EDT Wed Jul 23 2014

Friday should be one more quiet day, with lower dewpoints and
temperatures still a few degrees below normal. A disturbance flowing
down within the northwest flow aloft will run into the dry air over
us, which should keep us from getting rain. This first system could
set the stage for another system to have a little more moisture to
work with late Friday night as it gets into southern Indiana. Cloud
cover with this system, similar to today, will pose a large question
mark on temperatures and rain chances in the day Saturday. MEX
guidance is calling for highs in the 90s Saturday, with the chance
for storms waiting until the evening as yet another disturbance
rolls through and takes advantage of that heating/instability. Will
not go as high as the guidance for temperatures, but still be around
90 for many locations.

The rain chances will continue Sunday and Sunday night as we get a
cool front to move from the Midwest into the Ohio Valley. That front
will bring another round of unseasonably cool temperatures to the
region for at least the first half of the work week. Once again,
records are possible with this round of cooling.

&&

.AVIATION (06Z TAF Update)...
Issued at 118 AM EDT Thu Jul 24 2014

A somewhat low confidence forecast for this TAF package as we deal
with low stratus -- always a difficult thing to forecast and rather
uncharacteristic for late July.  Climatology shows that central
Kentucky experiences sub-VFR ceilings during the pre-dawn hours in
July only about 10% of the time (1973-2011).

Anyway, low ceilings have indeed developed along the Ohio River
Valley early this morning and are expected to persist for several
hours.  Ceilings should concentrate around the low end of MVFR, but
could slip briefly to high end IFR around dawn.  Visibility should
not be restricted.

The question with this kind of cloud deck is always how quickly it
will lift and/or mix out.  The models are having their usual
disagreements.  At this point will go with a gradual diurnal lifting
of the clouds, reaching VFR by this afternoon though remaining BKN
for much of the day.  Skies should clear out tonight.

Winds have been chaotic over the past several hours as various
synoptic and mesoscale boundaries move through the region.  However,
winds should concentrate out of the NNW for the pre-dawn hours and
NNE during the day today at speeds of 5 to 10 knots.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Update.........BJS
Short Term.....AMS
Long Term......RJS
Aviation.......13



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