Scientific Forecaster Discussion
fxus63 klmk 171126
Area forecast discussion
National Weather Service Louisville Kentucky
626 am EST sun Nov 17 2019
..updated aviation discussion...
Short term...(today and tonight)
updated at 315 am EST sun Nov 17 2019
Other than some patchy fog this morning, expect another quiet day.
There will be increasing upper sky cover ahead of a shortwave trough
that approaches the region tonight. Highs are expected to be a tick
milder than Saturday, peaking in the upper 40s and low 50s in most
spots. A few of our far southeast counties may see mid 50s under more
A sharp shortwave trough axis will pivot into the Wabash and Ohio
River valleys after midnight tonight, bringing meager but sufficient
moisture to possibly squeeze out a few measurable showers, mainly
along and north of the I-64 corridor. The biggest issue is whether
precipitation will be liquid?. looking at soundings and forecast
surface temps, think we'll stay just warm enough to support rain.
However, there is a scenario where surface temps dip just below
freezing in spots. Given that saturation will not be deep/cold
enough to support ice crystals for snow technically we could see
drizzle/freezing drizzle too. Wouldn't expect any issues if freezing
drizzle did occur because Road temps would be too warm, precip will
be very light and short-lived. Overall, not a big deal and most
spots will stay dry anyway.
Long term...(monday through saturday)
updated at 300 am EST sun Nov 17 2019
A compact shortwave trough embedded within a larger eastern Continental U.S.
Longwave trough will be moving through the region Monday. Forecast
soundings reveal limited moisture in the profile, but there may be
enough forcing to get some isolated showers out of the setup, mainly
along and north of the I-64 corridor. The trough should push east of
the region by Monday evening, but another compact shortwave trough
may come swinging in from the northwest by Tuesday morning. Will
keep pop chances in the low range since model guidance varies quite
a bit on the timing and placement of these shortwave troughs.
After Tuesday, upper level ridging begins to build into the region.
This will result in dry conditions and a return to "warmer"
(climatological normals) temperatures by midweek. Wet weather
returns Thursday as a cold front pushes toward the region. We may
see a brief dry period before another system takes aim at the region
late Friday into Saturday bringing another round of precipitation.
Aviation...(12z taf issuance)
issued at 626 am EST sun Nov 17 2019
The only concern early this morning will be some light fog potential
at the taf sites. Will start them right around the VFR/MVFR
threshold with drops into MVFR through 14z possible. Otherwise
expect VFR with some upper clouds streaming overhead and generally
light and variable winds 5 knots or less through the rest of the day.
VFR ceilings do move into the area overnight, but will mostly stay
10 k feet or above at sdf/Lex/bwg. Hnb could see some MVFR ceilings
and a few light showers right at the end of the valid forecast time
frame. Sdf extended out to Monday 18z could also see some MVFR
ceilings and a few light shower toward the end of the cycle.