Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 210525
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
125 AM EDT Mon Jul 21 2014
...Updated Aviation Discussion...
Issued at 948 PM EDT Sun Jul 20 2014
Skies have been continuing to clear out across the forecast area
with some clouds lingering in portions of southern and eastern KY.
This, along with very light to calm winds and plenty of low-level
moisture sticking around yields a decent chance for patchy fog
throughout central KY and southern IN. The better chances for fog
development (outside of prone locations) will be concentrated to
locations that received rain today, particularly in the Bluegrass
region. Increasing confidence exists for areas of fog to develop in
and around rivers, valleys, and other prone spots and have updated
the forecast as such. As for temperatures, have bumped lows down a
degree or two to account for radiational cooling expected under the
mostly clear skies. Dewpoints have also been adjusted accordingly.
.SHORT TERM (Now through Monday Night)...
Issued at 315 PM EDT Sun Jul 20 2014
A broad area of high pressure at the surface will stretch along the
northeastern seaboard back into Kentucky through the short term.
Aloft the trough over the area will shift eastward tonight. Ridging
building across the western CONUS will edge closer to the area with
heights rising aloft.
A few showers remain across the Bluegrass this afternoon. These will
slowly continue to work their way eastward and should move out of
the area by evening. Clouds will begin to dissipate tonight with
partly cloudy skies expected by morning. Ample low level moisture
will remain in place across the region, however. With light winds
and clearing skies, some patchy fog may develop after midnight. Lows
tonight will be in the mid to upper 60s.
For tomorrow went ahead and removed precipitation chances from the
forecast. With the ridge building aloft and capping over the area,
think that any showers or storms will stay east of the area. Dry
conditions will continue Monday night. We will be warming up some
more tomorrow with highs in the upper 80s to around 90 expected.
Lows tomorrow night will be in the upper 60s to lower 70s in urban
.LONG TERM (Tuesday through Sunday)...
Issued at 315 PM EDT Sun Jul 20 2014
Upper level ridging looks to bring hot temperatures to the Ohio
Valley during the first few days of the long term period. Expect
temps to top out in the low to mid 90s both Tues and Wed with night
time lows in the upper 60s and lower 70s. Ridging will provide a
strong cap over much of the area Tues suppressing any t-storm
activity although the cap will be noticeably weaker in the Lake
Cumberland region according to model soundings and thus a few storms
aren`t out of the question Tues afternoon/evening in that area.
The next solid rain/t-storm chance will arrive late Wed afternoon
into Wed night as an upper trough and cold front dive southeast into
the Ohio Valley. Isolated to scattered storms look possible Wed
afternoon ahead of the main complex of storms along the cold front.
Sfc instability has the potential to rise to decent levels with the
hot air mass in place but cloud cover from afternoon storms or
storms upstream may limit the amount of instability available for
the main complex of convection arriving Wed night along the cold
front. At this point, strong storms still look possible late Wed
into Wed night. However, the evolution of pre-frontal storms and
downstream convection may play a significant role in determining the
strength of storms in our area Wed night. The main threats from any
strong storms that do develop would be gusty winds, small hail, and
briefly heavy rainfall.
Convection should exit the area early in the day Thurs with high
temps dropping back into the upper 70s and lower 80s.
Friday looks to be a pleasant day with mostly dry conditions across
the area and partly cloudy skies. A stray shower or storm may be
possible over south central KY depending on how far south the cold
front settles and if it wobbles back north a bit on Friday. Overall
though think that the precip chances will remain to our south and
east with high temperatures in the low to mid 80s over the Ohio
A significant upper trough looks to make its way into the upper
Midwest for next weekend. Convection will probably occur with
boundaries and waves associated with this feature, but model
solutions vary widely on the finer details including timing. Thus
will keep POPs low at this time due to a low confidence forecast.
Temperatures look to remain below normal through next weekend with
highs in the low to mid 80s and lows in the 60s.
.AVIATION (06Z TAF Update)...
Issued at 115 AM EDT Mon Jul 21 2014
Main challenge is potential for overnight fog formation. Skies have
cleared and winds have gone nearly calm, with favorable radiational
cooling conditions expected to continue. Most concerned about LEX,
where temp is already close to the afternoon dewpoint, and over a
half inch of rain fell late Sunday afternoon. Latest GFS LAMP
guidance has backed off a bit from previous runs, but still
confident that restrictions to vis will occur. As this discussion
was about to be sent, LEX came in with IFR visibility, so will
initialize accordingly closer to the end of the issuance window,
and most likely include a TEMPO for LIFR vis. Didn`t quite hit
BWG as hard and confidence a bit lower due to some slightly lower
dewpoints that mixed down Sunday afternoon, but stuck with a
similar theme of prevailing MVFR/TEMPO IFR. SDF should stay warm
enough to limit impacts to a couple hrs of MVFR vis around
By mid-morning the fog should dissipate, leaving VFR conditions with
only scattered diurnal cu and light ENE winds.