Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 271729
Area Forecast Discussion
National Weather Service Louisville KY
129 PM EDT WED JUL 27 2016
...Updated Aviation Discussion...
Issued at 1055 AM EDT Wed Jul 27 2016
Quick update forthcoming to remove early morning wording. Otherwise
the convective forecast seems to be on track, with the best chances
in between the WK/BG Parkways and the Cumberland Parkway as the day
progresses. Still appears that we`ll have up to 50 percent coverage
over the course of the afternoon, but a snapshot would not show much
more than isolated coverage at any given time. Main threat will be
torrential rainfall, as is already evident in Ohio County where
around 3 inches of rain fell this morning.
.SHORT TERM (Now through Thursday)...
Issued at 320 AM EDT Wed Jul 27 2016
Partly to mostly cloudy skies were noted across the region this
morning. Temperatures remained rather mild with readings generally
in 70s. Weak isentropic lift across the southern parts of the
region has been generating some showers across the TN plateau.
Latest high res models suggest that these will lift northward into
southern KY over the next few hours. So have increased PoPs a bit
across areas south of the Cumberland/Nunn Parkway region. Some
patchy fog will also be possible through sunrise, though the overall
areal extent will be less than yesterday morning.
For today, generally have kept a persistence type forecast going as
a weak boundary draped across the region will serve as focus for
renewed convective development. Initial convection will likely be
limited to southern KY early this morning. Insolation across the
north should allow temperatures to hit their convective temps by
early afternoon resulting in scattered convection. Flow aloft
remains rather weak, so widespread organized severe convection looks
rather low. However, plentiful moisture and pockets of instability
will result in storms producing heavy rain/gusty winds/lightning
this afternoon. Highs look to warm into the upper 80s to around 90.
Convection will likely become more isolated tonight with the setting
sun. Lows look to cool into the 70s once again.
Well advertised mid-level trough axis will approach the region late
tonight and on Thursday. This feature combined with plenty of
moisture and instability will result in more widespread convective
development. Previous forecasts have had this covered, and only
minor increases to cloud cover and PoP were required. Flow aloft
remains weak, but moisture will continue to increase. Strong storms
will be possible where pockets of instability can develop during the
day. Main threat for Thursday will be heavy rainfall and gusty
winds. Locally heavy rainfall will be possible given that
precipitable water values will be well over 2 inches within the
column. Widespread 1/2 to 1 inch rainfall looks likely during the
day with some localized areas of 1 1/2 to 2 1/2 inches being
possible. This rainfall may result in some local flooding issues by
the end of the day. Depending on rainfall today, a Flash Flood
Watch may be required for some areas on Thursday should the heavier
rains materialize. Temperatures will be below normal on Thursday
with highs generally in the lower 80s.
.LONG TERM (Thursday night through Tuesday)...
Issued at 340 AM EDT Wed Jul 27 2016
In the long term period, the upper flow pattern will feature a
western CONUS ridge with a rather large trough axis across the
eastern US. The latest round of guidance suggests that this eastern
trough axis will likely persist throughout the weekend before
lifting off to the east by early next week. Ridging looks to build
into the region early next week as a mid-level ridge attempts to
rebuild across the central CONUS. The ridge will likely struggle as
a fast westerly flow will remain in place across the northern third
of the US. A stronger signal in the data suggests that heights will
fall again across the eastern US by the end of the week resulting in
the pattern reverting back to a western CONUS ridge and eastern
CONUS trough type pattern as we end next week.
In terms of sensible weather, the persistence of the upper trough
axis across the eastern US will result in a continued unsettled
weather pattern for the Ohio Valley. Several mid-level perturbations
will move through the region resulting in episodic bouts of showers
and storms...mainly diurnal in nature. Previous forecasts were a
bit too optimistic on the trough clearing out, so the forecast has
been adjusted to keep shower/storm chances in through at least late
Sunday. A slightly drier trend looks to develop by Monday and
Tuesday as heights build across the region. Temperatures through
the period look to remain seasonal for late July and early August.
Daytime highs in the upper 80s with overnight lows in the lower 70s
still look good through the period. A more significant cooldown may
be in the offing beyond the current forecast period as the ridge
axis breaks down and shifts back to the western US.
.AVIATION (18Z TAF Update)...
Issued at 125 PM EDT Wed Jul 27 2016
Another difficult forecast this time frame as no large scale
features to focus on. Stagnant air mass remains in place over all
TAF sites, and convection initiation will once again depend upon
subtle outflow boundaries lingering from storms of the past 24
Anvil remains of morning storms now have SDF overcast, but radar
still showing some small cells trying to take off. Tropical air mass
resulting in storms producing torrential rains but little if any
Bottom line...amendments will be likely once thunderstorms develop
and locations are better defined.