Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 131045
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
645 AM EDT THU JUN 13 2013
...Updated Aviation Discussion...
.SHORT TERM (Today through Friday)...
Issued at 254 AM EDT Thu Jun 13 2013
A strong mid level cap kept our weather quiet overnight, and will
likely continue to do so early this morning. However, a cold front
was still to our west at 06Z from low pressure over southern
Michigan through central Illinois to Oklahoma. Also, a
strengthening upper shortwave trof was swinging southeastward across
northern Illinois. Until these features clear the region later this
morning, we can`t completely let our guard down. So, will have just
a very small chance of showers/storms for the morning hours. Behind
the front and upper wave this afternoon even those small rain
chances will evaporate.
We should still have a few hours of heating this morning before the
front moves through, with high temperatures in the lower and middle
80s. This afternoon temperatures should be nearly steady, or may
even fall a degree or two -- quite a feat for mid June! Northwest
winds behind the front will gust into the 20 to 25 mph range.
Tonight winds will become light and skies clear. However, no fog is
expected since dry air will be advecting into the region. Low
temperatures should be in the upper 50s to lower 60s. Dew points
will drop into the comfortable middle 50s by sunrise.
Friday will be a pretty day as Canadian high pressure builds in from
the north. With sunny skies in the morning and fair weather cu in
the afternoon, temperatures will top out around 80 degrees.
.LONG TERM (Friday Night - Wednesday)...
Issued at 257 AM EDT Thur Jun 13 2013
A ridge...trough...ridge pattern at 500mb will be in place late
Friday as a deep trough exits New England. Out west, a potent but
small closed low will flatten ridging over the northern Rockies as
it moves east of the Canadian Rockies. By early Monday, this closed
low will elongate along an east-west axis across southern Canada as
moderate 500mb flow undercuts this trough. This will produce a zonal
flow over the lower Ohio Valley for Sunday and Monday.
At the surface, Canadian high pressure over the western Great Lakes
late Friday will be responsible for a dry airmass and seasonably
cool overnight lows both Saturday and Sunday morning. After lows
near 60, highs on Saturday will warm a few degrees over Friday`s
highs, with temperatures peaking in the mid 80s. With the proximity
of this high Saturday afternoon expect mostly clear skies in the
morning with a few afternoon fair weather cumulus in the afternoon.
Winds will stay light and variable even into Saturday afternoon.
Southwesterly flow will develop by early Sunday along the backside
of this departing surface high. Gulf moisture, previously restricted
to along the Mississippi River Valley, will move east and bring more
humid weather for Sunday through Tuesday.
Episodic convection is possible Sunday through Tuesday as Gulf
moisture, with PWATs as high as 1.5 inches pools across an area
lying from Missouri through southern Ohio. This area will lie south
of a east-west orientated surface trough roughly across the southern
Great Lakes. Both the GFS and ECMWF develop at least the possibility
of scattered storms early Sunday across southern Indiana, as the
first of several weak waves approaches. Think that most locations
will get at least some rain Monday as moisture is maximized ahead of
a slowly sagging boundary forecast to lie across central Indiana.
Will maintain current likely pops for Monday. A trough is forecast
to move across the Great Lakes late Monday. This will finally push
a surface boundary southward into the Commonwealth. By late
Tuesday, drier air will begin to filter in from the north. Dry
weather and lower dewpoints are forecast for Wednesday.
Temperatures Sunday through Tuesday may be modified by clouds and
scattered convection. However, temperatures shouldn`t stray too far
from normal, with highs in the mid 80s and lows generally in the
.AVIATION (12Z TAF Update)...
Issued at 644 AM EDT Thu Jun 13 2013
A strong upper shortwave trof and surface cold front remain to our
northwest, leaving a small chance for convection to still affect
SDF/LEX this morning. However, strong capping has kept things
very quiet so far as CONVECTION moves by to our north. Will play
down thunder chances with a simple VCSH through the morning hours.
Really, the main issue for aviation during this TAF period will be
the winds. Ahead of the approaching front, winds will continue out
of the WSW, occasionally gusting to around 20 knots. The passage of
the front will bring winds around to the northwest, and gusting into
the 20 to 25 knot range late this morning into this afternoon.
Winds will settle down with sunset tonight.
Another concern is a patch of low clouds currently behind the front
over central Illinois. Model guidance seems to want to slightly
break up this cloud field and lift it a bit. For now will bring it
into the TAFs at the lowest possible VFR height, but pilots should
be aware that ceilings may need to be lowered in the TAFs if it
appears that the area of clouds is not breaking up or lifting as it