area forecast discussion
National Weather Service Louisville Kentucky
255 PM EDT Wednesday Jun 19 2013
Short term (now through Thursday night)...
issued at 255 PM EDT Wed Jun 19 2013
Benign weather pattern this period. High pressure to our north will
shift southeast into the Atlantic Thursday. Tonight a shortwave
ridge will cross the region followed by a very weak trough Thursday
as a stronger ridge pushes into the mid Mississippi River valley.
Despite the slightly cooler air aloft with the trough, drier than
normal precipitable waters will mean little if any rain chances.
Forecast surface analysis does indicate a weak inverted trough,
which may serve as a focus for brief development during peak
heating. Current forecast has very low pops. Will trend up some, but
keep pops just under mentionable levels (i.E., 14 percent at most).
Temperatures could dip into the upper 50s in our cool spots over the
Bluegrass tonight, whereas most other sites will see low/mid 60s.
Highs tomorrow should rise into the mid/upper 80s, followed by
another night in the 60s.
Long term (friday through wednesday)...
issued at 255 PM EDT Wed Jun 19 2013
The long term period will feature a rather expansive eastern ridge,
with a trough centered across the western states. This large ridge
will dominate the sensible weather through the long term period,
bringing the first prolonged heat wave of the Summer to the Ohio
Valley.
Friday through the first part of next week will be characterized by
very weak tropospheric flow. However, as a surface ridge slides
east by Friday, southerly winds will begin to draw in more
moisture. Forecast soundings show little in the way of convective
inhibition Friday through early next week, so thermal circulations
brought on by diurnal mixing and weak density gradients will be the
focus for isolated thunderstorm activity, generally in the
afternoons and early evenings of each day. Instead of going with
blanket slight chance pops each day, have tried to use forecast
pwats and ensemble guidance to pinpoint the best locations for
precipitation each day. No day will be a washout for any location
by any means, but an isolated thunderstorm will be possible each
afternoon beginning Friday through the first part of next week.
The main story of the long term period will be the building heat.
850mb temps will climb from 17c on Friday, closer to 20c by the end
of the long term period. While those temperatures are not overly
oppressive, given the expected abundance of sunshine and sun angles
nearing their yearly maximum, daytime heating should be rather
efficient. Additionally, any lingering ground moisture may quickly
dry out with little expected precipitation and copious sun for
several days. All this being said, expect highs in the upper 80s on
Friday, warming slightly each day to the lower 90s by Tuesday and
Wednesday. Heat indices will approach the middle 90s by the start
of next week.
&&
Aviation (18z taf update)...
issued at 115 PM EDT Wed Jun 19 2013
Have a weak cold front across south central Kentucky this afternoon,
with a thin line of 4 kft cumulus. An isolated storm is not out of
the question for later this afternoon, but the chances are too low
to have in a taf for bwg at this time. Winds will be light and
generally from the northeast today, with high pressure centered over
Lake Huron. That high will shift to our east Thursday, which should
change the prevailing direction to east/southeasterly. Drier
dewpoints over the area should prevent US from getting fog in the
morning.
&&
Lmk watches/warnings/advisories...
in...none.
Kentucky...none.
$$
Short term.......rjs
long term........kd
aviation.........Rjs
