Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Louisville Kentucky
1254 am EDT Tue Jul 7 2015
..updated aviation discussion...
Short term (now through Tuesday night)...
issued at 325 PM EDT Mon Jul 6 2015
Late this afternoon, satellite imagery indicated cu to our west
trying to grow upscale but largely being inhibited by ridging over
the Ohio Valley. Still can't rule out a stray shower/storm along
and west of I-65 this evening as peak instability is reached and the
ridge continues to gradually shift east, thus, will continue 20%
A cold front will approach the area tonight and tomorrow.
Precipitation should stay mainly to our west overnight with the
cloud shield from convection along the front overspreading our
region after midnight. Although the atmosphere should largely stay
too mixy for fog formation, think that some light patchy fog may be
possible over east central Kentucky late tonight into tomorrow morning.
Lows should reach the upper 60s to lower 70s tonight.
For tomorrow, isolated to scattered showers and storms are expected
in the morning with convection becoming more numerous during the
afternoon hours as the front draws near and storms tap into
afternoon instability. Soundings indicate that initially storms
could be strong to severe with damaging winds the main threat.
Storm Mode will be mainly multicell clusters throughout the
afternoon and evening hours. If we get morning convection or a lot
of cloud cover early in the day, afternoon instability may suffer to
reach projected values and thus limit storm strength. Will need to
fine tune convective coverage and strength as event evolution
becomes more clear over the next 12-18 hrs. Either way, multiple
rounds of showers and storms are expected from tues afternoon and
through the overnight hours tues night. Precipitable water values
climb to 2-2.25 inches tues evening and overnight which points to
more heavy rainers for the region. The latest short range models
indicate that southern in/northern Kentucky may be susceptible to the most
convection tues/tues night and thus heavier rainfall totals.
Although the area has had time to recover from recent rains and
flash flood guidance has improved, think that locations that receive
multiple rounds of storms may see some minor flooding problems by
late tues night into Wed.
Temps tues should be limited to the mid to upper 80s. Lows tues
night should range through the upper 60s and lower 70s and may be
tricky depending on how far southeast the cold front makes it.
Long term (wednesday through monday)...
issued at 300 PM EDT Mon Jul 6 2015
The long term period will begin with zonal flow aloft over the lower
Ohio Valley. Ridging will begin to build in from the south by the
end of the week and really amplify across the region this weekend.
At the surface a stalled frontal boundary will be in place Wednesday
across the forecast area. This will eventually lift back to the
north as ridging builds in.
Wednesday and Thursday will both see isolated to scattered storms as
a couple of waves ride along the stalled front. The focus for
activity looks to be across the northern half of the region. South
central Kentucky will likely be mostly dry, but have kept isolated storm
chances during the day as outflow boundaries could serve as a focus
for storms during peak heating.
As the upper level ridge builds across the region any chances for
storms will shift off to the northeast. Mostly dry conditions are
expected this weekend. However, portions of southern in and the
northern Bluegrass could see a few storms as disturbances round the
edge of the ridge.
In addition to drier conditions, temperatures will warm with the
ridge building in. Highs Friday through Sunday will top out in the
lower 90s in many locations. Combined with dewpoints in the lower
70s, heat index values will rise to near 100 each afternoon. Lows
through this time period will be in the lower 70s.
Aviation (06z taf update)...
issued at 1251 am EDT Tue Jul 7 2015
Generally VFR conditions are expected the rest of the overnight into
today outside of thunderstorms, but incoming convection will
likely bring brief restrictions to all sites through the period.
The latest guidance suggests there may be two rounds of convection
today, the first which will come towards dawn and last through the
mid morning. It appears ksdf has the best chance of seeing this
activity, but it could get into klex and kbwg as well.
After that pushes through, there may be a bit of a lull late this
morning into the early afternoon before yet another round of
convection fires along an approaching cold front. Have tried to
time the best chances for convection, but admittedly a thunderstorm
will be possible at all sites through any Point of the day today
into this evening. Outside of convection, SW winds will gust in
excess of 20 knots at times, but should die down this evening once
the sun sets.