Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 041023
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
623 AM EDT Mon May 4 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Tuesday)...
Issued at 300 AM EDT Mon May 4 2015
A surface analysis early this morning featured high pressure off the
North Carolina coast while a frontal boundary lied from north
central Wisconsin southwestward through Iowa into Kansas. Aloft,
water vapor imagery overlaid with 500 mb heights showed mainly zonal
flow across the CONUS with shortwave troughs moving through the
Upper Midwest and central Plains. Locally over the Ohio Valley,
mostly to partly clear skies prevailed with light/variable winds.
Early morning readings were in the mid/upper 50s.
For today, another seasonably warm day is on tap as surface high
pressure and ridging aloft builds across the southeast US. Plan on
readings to max out in the low/mid 80s. Sky cover will be variable
as high clouds from convection to our northwest spills over the
region but should be an overall partly cloudy day.
04.00z guidance shows one of the aforementioned shortwave troughs to
push from Iowa into central Indiana and Ohio later today. As the
surface front approaches but then stalls to our north, the
combination will act to initiate showers/storms across Indiana. The
main question is how far south will this develop. The NAM/SREF are
the more aggressive solutions, bringing precip as far south as
south-central KY. However, the GEM/GFS/ECMWF deterministic runs keep
the forecast area dry. A look at the hi-res suite, the NSSL and SPC
WRF runs do show isolated late afternoon convection across parts of
our southern Indiana counties (Orange to Jefferson IN). Soundings
for these locations exhibit MLCAPE around 1000 J/kg with modest
mid-level lapse rates in an uncapped environment. With the upper
forcing passing by as well, feel there support for a stray late
afternoon, early evening shower/storm. As a result, introduced
slight chance afternoon POPs across the far north.
A dry/mild night is then expected as the front stalls west to east
from northern Iowa through north central Indiana and Ohio. We`ll
have light southwest winds under mostly clear skies. Plan on lows
in the upper 50s to around 60 and highs 80-85.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 300 AM EDT Mon May 4 2015
A relatively dry pattern with temperatures warming solidly into the
80s is on tap for mid to late week. The pleasant weather will be
courtesy of a REX block setup. Will continue to side with drier
models given the pattern. The 0Z GFS/0Z GEM do bring the tropical
system farther inland on Thurs which may spread moisture a bit
farther north and west closer to our region. Will need to monitor
evolution of this tropical system in coming days, but don`t feel a
POP is necessary for Thurs attm.
The upper ridge really doesn`t start to break down over our area
until this weekend with varying time frames on when that will
actually occur. Will side with the slower models given "slower" has
been the trend in the past few days. So will start low POPs on
Sunday as ripples in the upper level flow start to provide triggers
for convection. Then an upper trough arrives for the beginning of
next week bringing better precip chances for Mon.
For temps, highs will range from the low to mid 80s throughout the
week with perhaps the warmest days being Fri/Sat where many
locations will reach the mid 80s. Low temps will range from the
upper 50s to lower 60s.
.AVIATION (12Z TAF Update)...
Updated at 618 AM EDT Mon May 4 2015
Plan on VFR conditions at SDF/LEX/BWG through the TAF period.
Scattered to broken high level clouds will move overhead at times
during the day and winds will be generally out of the south between
10-12 kts by afternoon. Some afternoon gusts near 20 kts are
Outlook: Above average confidence for VFR conditions through at