Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 211927 AAA
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOUISVILLE KY
327 PM EDT Mon Jul 21 2014
.SHORT TERM (Now through Tuesday Night)...
Issued at 315 PM EDT Mon Jul 21 2014
Upper level ridging will continue to build in from the west through
Tues. This will result in hot, humid conditions over the area.
High pressure at the sfc will keep the hot, humid airmass relatively
stagnant and unhealthy for sensitive groups on Tues. Thus an Air
Quality Alert has been issued for the Louisville Metro area for Tues.
Temperatures will warm slightly for tomorrow with afternoon highs
expected to reach the 88-94 degree range. Although the airmass will
be warmer than today, we won`t see strong southerly sfc flow and the
hottest temps in the ridge axis are expected to remain to our west
so will stray away from mid 90s for highs. Low temperatures look to
be in the upper 60s and lower 70s tonight and then solidly in the
lower 70s for Tues night. Also some patchy fog will be possible
There is a 20-30% chance for some afternoon/evening convection on
Tues mainly south of a line from Bowling Green to Lexington. Capping
will be weaker in this location and energy from an upper low over
the Gulf states may spur convection as far north as the KY/TN
border. Any storms that do form are not expected to be organized or
severe. The best storms may contain wind gusts up to 40 mph and
briefly heavy rainfall.
.LONG TERM (Wednesday through Monday)...
Issued at 312 PM EDT Mon Jul 21 2014
The start of the long term will feature a strong ridge across the
western CONUS with a trough across the east. This pattern will
continue through the long term, though the trough across the east
will begin to deepen towards the end of the period while the axis of
the western ridge shifts westward.
Precipitation chances will be on the increase Wednesday. For the
daytime there will be two features that will bring precipitation to
central KY and southern IN. The first is a weak wave that will move
across south and east central KY. This will spark showers and
thunderstorms during the morning hours across southern and eastern
portions of the forecast area. At the surface a cold front will
approach and move through the area Wednesday into Thursday night.
Storms will develop along and ahead of this front. These will move
in to southern IN during the late morning into the afternoon and
spread across central KY from the afternoon into the evening. A weak
low will ride northeast along the front from the evening into the
overnight hours. This will help enhance shower and thunderstorm
coverage. As mentioned in the previous discussion, there will be
plenty of instability but shear will be weak with this system, so
organized severe weather is not expected. Heavy rain with some
ponding of water will be possible as PWATS rise to 1.8-1.9 inches.
Precipitation chances will decrease from west to east on Thursday as
the front continues southeast. Dry and less humid conditions are
expected Thursday night through Friday night in the wake of the
The next chance for showers and storms will begin Saturday as
another front moves into the area. Rain chances will continue into
Sunday as disturbances round the base of the deepening upper level
trough. Beyond the long term it continues to look like we will see
another significant cooldown midweek next week with highs
potentially in the 70s.
.AVIATION (18Z TAF Update)...
Issued at 125 PM EDT Mon Jul 21 2014
The main TAF challenge with be reduced vsbys in light fog tonight at
BWG and LEX. According to the latest MOS guidance and model
soundings, enough low level moisture should still exist for fog
formation under light winds and a weak inversion. Went with MVFR
vsbys at both sites for this TAF forecast, but think that LEX vsby
may go down to IFR especially after having dense fog there this
morning. Some guidance suggests this as well while other guidance
remains more optimistic, therefore, will keep forecasted vsby in the
low end MVFR cat for now. Otherwise VFR conditions will prevail.
Winds will remain easterly this afternoon and then southerly for