Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Louisville Kentucky
708 PM EDT Mon Sep 1 2014
..updated aviation discussion...
Short term (now through Tuesday night)...
issued at 303 PM EDT Mon Sep 1 2014
A cold front stretching from the Great Lakes to the Red River valley
will sag southeastward this evening. Tonight a strengthening low
level jet will impinge on the front as a shortwave trof slides in
from the northwest. With plenty of moisture available, showers and
thunderstorms will develop from Oklahoma to Indiana overnight. This
activity will push into the Ohio Valley by morning. Timing of this
rainfall is difficult to nail down, but right now it looks like wet
weather will become widespread across southern Indiana after
midnight, into the Louisville Metro and Ohio River counties a few
hours either side of dawn, and into the rest of central Kentucky
during the day Tuesday.
Over the course of the day Tuesday showers and thunderstorms will
remain a good bet. The initiating cold front will be dissipating,
but enough boundaries and instability will be in the area to
continue chances of convection. Locally gusty winds will be the
main threat from any stronger cells.
Tuesday night any remaining storms in the Lake Cumberland region
will gradually taper off and/or exit to the southeast. Patchy fog
looks like a good bet after midnight, though lingering cloud cover
may put a monkey wrench in that.
Tonight will be very warm and muggy with lows only in the lower and
middle 70s. There will be a slight breeze from the south around 5
to 10 mph, but it will still be uncomfortable for folks without air
High temperatures on Tuesday are challenging given the clouds and
rain in the area, but lower to middle 80s sound about right.
Tuesday night will be a little cooler behind the front, with
temperatures dropping into the middle and upper 60s.
Long term (wednesday through monday)...
issued at 303 PM EDT Mon Sep 1 2014
Wednesday through Thursday...
In the wake of a progressive yet shallow 500mb trough exiting New
England, ridging will build northwards over the Tennessee and Ohio
valleys from Wednesday through late Friday. As upper heights build,
expect a warm and humid period that will feel a lot like mid Summer.
With the storm track well north across the upper Midwest, rain
chances will stay sparse with just isolated afternoon and evening
convection at best. Despite recent ample rains, highs will still
approach or just exceed 90 degrees. Expect warm muggy nights with
lows near or just above 70.
Friday through Monday...
A shallow progressive upper trough will move across the northern
Great Lakes Saturday into early Sunday. In the wake of this system
surface high pressure of Canadian origin will sink southwards across
the upper Midwest and eventually the Northern Ohio valley. Ahead of
this though, an elongated cold front will slowly sag southwards
through Illinois and Indiana late Friday, possibly crossing the
commonwealth by early Sunday. This boundary, which will run roughly
parallel to the mid-level flow will be slow moving. One or more
rounds of convection will accompany this boundary due to pre-frontal
convergence and moist air. Friday night and Saturday will provide
the best chance for storms based on a compromise on the speed of
this front. Some showers may linger Sunday morning across our
southern counties, however, by afternoon cooler and distinctly drier
air will arrive from the north. Friday's highs will approach 90,
with highs only in the mid-80s for an expected mostly cloudy
Saturday. Sunday will become much less humid with clearing and a
high only in the upper 70s to around 80.
High pressure will become centered over the Great Lakes on Monday,
with northeast winds expected across the commonwealth. With mostly
clear skies expected after morning lows possibly in the 50s, highs
will reach the upper 70s to around 80.
Aviation (00z taf update)...
issued at 707 PM EDT Mon Sep 1 2014
Scattered showers with continue to move northeastward across
southern Indiana and portions of northern Kentucky this evening.
Best chances of seeing any shower activity would be at ksdf through
about 02/03z. Will continue to monitor ksdf closely this evening
and amend if necessary. Elsewhere at kbwg and klex, expect VFR
conditions at those terminals. Winds will remain out of the
southwest this evening at 5-10 knots. Winds are expected to drop
below 6 knots after 02/03z at all the terminals.
Surface cold front is still expected to approach the region late
tonight. Late afternoon model solutions suggest convective activity
upstream in western Missouri will continue to develop and then
spread eastward toward southern Illinois and western Kentucky late tonight.
Expect showers and possible storms to re-enter the kbwg and ksdf
terminals after 02/10z and then into klex after 02/12z. These times
may need to be bumped up in subsequent forecasts as we see
convective evolution take place out to our west.