Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 270725
Area Forecast Discussion
National Weather Service Louisville KY
325 AM EDT SAT AUG 27 2016
.SHORT TERM (Now through Sunday)...
Issued at 305 AM EDT Sat Aug 27 2016
Expect today to be largely a repeat of Friday as a strong upper
ridge centered over Virginia extends westward across the Ohio
Valley. The ring of fire was active overnight as storms over the
Tennessee Valley lifted NW into western Kentucky, and are now
weakening over SW Indiana.
With convective temperatures solidly into the 90s over most of
Kentucky, will keep most of the area dry for today and tonight. Will
carry slight chances over southern Indiana, as leftover boundaries
from the weakening cluster of storms to our west could light up this
afternoon. Also will carry slight chance over south-central
Kentucky, as storms from Tennessee could edge NW just across the
border. Temps will again reach the lower 90s, with heat index values
approaching 100 this afternoon.
Confidence decreases on Sunday, as the ridging remains strong, but
the synoptic models suggest that an MCS could develop along the
quasi-stationary front over Illinois/Indiana and dive southward into
the Ohio Valley by early Sunday. Will bring chance POPs into
southern Indiana first thing Sun morning, and expand across central
Kentucky through the day as outflows and differential heating could
finally focus convection.
.LONG TERM (Sunday night through Friday)...
Issued at 300 AM EDT Sat Aug 27 2016
Upper ridge will remain oriented east to west across the Ohio Valley
through midweek, resulting in continued heat and humidity. Gradual
breakdown in the mid-level cap will allow for at least isolated
diurnal convection, so will continue to carry a 20-30 POP each
afternoon. Weak flow will prevent any organization, so SVR threat
Thu-Fri will see the pattern shift as a deep upper trof digs into
eastern Canada, and faster NW flow sets up over the Ohio Valley.
Latest GFS and ECMWF agree on a strong Canadian high building into
the Great Lakes, pushing a more pleasant air mass into the region.
This forecast reflects that with temps near or just below climo, and
dewpoints around 60. However, there still remains some bust
potential, mainly depending on the eventual fate of any tropical
activity, including the increasingly ragged 99L.
.AVIATION (06Z TAF Update)...
Issued at 140 AM EDT Sat Aug 27 2016
Mesoscale convective system (MCS) over western KY is moving north at
this time, sending dense cirrus clouds NNE into BWG and SDF. The MCS
also has caused a low-level outflow boundary to push NE across BWG,
causing their wind to go from calm or light NE to light W to SW. The
wind should again become calm overnight, but the boundary may help
keep fog from becoming an issue at BWG toward daybreak, although
still could see some MVFR vsbys at times. Vsbys around daybreak
should remain VFR at SDF and LEX.
During the day Saturday, high clouds will gradually dissipate as the
overnight MCS weakens. The area will still be under the influence of
a large ridge of high pressure aloft as surface winds become SE and
then S from 5-8 kt. Cannot rule out an isolated thunderstorm at BWG
and SDF (probably not LEX) during the late afternoon and early
evening, but coverage expected to be low so no inclusion of VCTS at
the TAF sites at this time. Thus, conditions will remain VFR with
scattered cumulus clouds around 4-5 kft during the afternoon.