Scientific Forecaster Discussion
fxus63 klmk 181745
Area forecast discussion
National Weather Service Louisville Kentucky
145 PM EDT Fri Aug 18 2017
..updated aviation discussion...
Short term (now through saturday)...
issued at 255 am EDT Fri Aug 18 2017
A cold front approaching the Ohio River before dawn will cross
central Kentucky this morning and usher drier air into the region
this afternoon. After some morning clouds we should see plenty of
sunshine this afternoon with temperatures rising into the mid 80s to
around 90. Dew points, however, will be 10 to 15 degrees lower than
yesterday resulting in lower humidity values.
Weak surface ridging will build in from the lower Mississippi Valley
this afternoon and tonight with mostly clear skies and nighttime
lows in the 60s. Some patchy valley fog can be expected around dawn
Saturday in the Lake Cumberland region.
Saturday surface low pressure beneath an upper shortwave trough will
move from Indiana to Ohio with a cold front trailing behind it. Most
of the moisture associated with this system will be between 700 and
500hpa, with drier low levels and precipitable water values only in
the 1.25-1.50" range. As a result, precipitation chances will be
low. The best shot at a shower or thunderstorm will be over southern
Indiana and the northern Blue Grass closer to the low. High
temperatures will be in the middle and upper 80s.
Long term (saturday night through thursday)...
issued at 305 am EDT Fri Aug 18 2017
Saturday night through Sunday night...
Ridging will build in at the surface and aloft over the southeast
United States, resulting in dry weather and typically warm
Upper ridging will remain in place, but the surface high will begin
to shift to the east. The GFS and gefs have really dried out, while
the eps still supports isolated convection, as does the fact that we
could get into some return flow as the surface high edges away. So,
while a stray pop-up thundershower can't be entirely ruled out, for
the most part it looks like an otherwise dry day with partly cloudy
High temperatures Monday afternoon will be a few degrees either side
of 90 with dew points around 70 west of I-65. Heat index values will
rise into the middle 90s...possibly briefly in the upper 90s in a
few spots...during the afternoon.
A cold front will sweep through the region from northwest to
southeast Tuesday and Wednesday, accompanied by showers and
thunderstorms. Pacific high pressure will then come in with dry
conditions Wednesday night and Thursday. Heat index values should
again climb into at least the middle and possibly upper 90s Tuesday
afternoon, but then cooler conditions can be expected Wednesday and
Aviation...(18z taf issuance)
issued at 140 PM EDT Fri Aug 18 2017
This taf period features largely VFR weather. The one exception is a
possible brief period of MVFR fog from 09-12z Saturday.
Scattered cu field is established around 4500 ft this afternoon,
with a 10 kt wind out of the west. Expect these clouds to
evaporate and winds to diminish and turn southwesterly after 00z.
Mainly clear skies are expected tonight. Mid-level clouds are
forecast to increase toward 09z Saturday an an upper level trough
approaches. A few light showers can't be ruled out north of I-64
Saturday morning, but the potential was too low to include in the
taf. Lex has the best shot at seeing a brief period of MVFR fog
Saturday morning. Otherwise, Saturday will be VFR.