Scientific Forecaster Discussion
fxus63 klmk 250706
Area forecast discussion
National Weather Service Louisville Kentucky
306 am EDT Tue Jul 25 2017
Short term (now through wednesday)...
issued at 258 am EDT Tue Jul 25 2017
An east-west dew point front is draped across central Kentucky. This
front will drop southward today, with higher humidity levels to its
south and more comfortable conditions to the north. Thunderstorms
will be possible in southern Kentucky once convective temperatures
of 87-89 are reached this afternoon. Precipitable water values are
only slightly above normal, soundings show significant capping, and
low and mid level winds will be very weak as upper ridging builds in
from the west. So, only isolated coverage is expected and should be
restricted to areas southwest of a Hartford-Brownsville-
Temperatures got a little warmer than expected yesterday and with
similar conditions today will go on the warm side of guidance.
Any afternoon convection will fall apart this evening, followed by a
quiet overnight. Valley fog will be possible by dawn. In the drier
air over the northern Blue Grass temperatures will dip into the
lower 60s, while the more humid conditions in the Bowling Green
region will prevent the Mercury from falling below 70.
Wednesday the dew point discontinuity will surge back to the north
ahead of low pressure over Kansas. Precipitable waters will still
not be impressive and mid-level lapse rates will be weak along with
continued weak low and mid level winds and ridging aloft. So, not
much more than an isolated storm is expected, primarily in the
Bowling Green region once again.
The increase in low level moisture/surface dew points on Wednesday
will lead to warmer afternoon heat index readings...creeping into the
upper 90s west of Interstate 65.
Long term (wednesday night through monday)...
issued at 305 am EDT Tue Jul 25 2017
Aloft the long term will be characterized by a heat ridge building
over the Southern Plains and Desert Southwest while general
troughing dominates in the northeast.
The first significant shortwave trough embedded in the flow will
cross the Great Lakes Thursday-Thursday night, with its associated
surface cold front scheduled to push through the Ohio Valley during
that time frame as well. The system will be accompanied by
widespread showers and thunderstorms, tapering off from north to
south on Friday.
Canadian high pressure will then move in to provide US with a
beautiful weekend. There should be plenty of sunshine with
comfortable humidity levels and highs both days 80-85. Actually on
Saturday some spots in the Blue Grass may not make it out of the 70s.
On Monday surface pressure will begin to drop and another upper
trough will move in, bringing a chance of showers and thunderstorms.
Aviation (06z taf update)...
issued at 1256 am EDT Tue Jul 25 2017
Surface analysis shows weak front draped across central Kentucky
early this morning with a dewpoint gradient between sdf/Lex and bwg.
With the better low-level moisture and light winds across southern
Kentucky, light fog may develop toward sunrise at bwg for a couple
High pressure nosing down from the Great Lakes region will provide
dry and VFR conditions at sdf and Lex through the taf period. Expect
some diurnal cu with bases 3-5 kft. At bwg, the stalled out front
near the Tennessee/Kentucky border and better low-level moisture may be enough
for a few pop-up afternoon showers or storms. Some of the hi-res
models hint at this developing around the bwg terminal after 18-21z.
For now, will leave out of the taf given the low confidence and low