Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 181501

Area Forecast Discussion
National Weather Service Louisville KY
1101 AM EDT Mon Sep 18 2017

.Forecast Update...
Issued at 1058 AM EDT Mon Sep 18 2017

An area of light to moderate rain continues to work its way east
across southern IN with scattered showers moving in behind it. This
area of rain should continue east over the next couple of hours.
Through the afternoon, scattered showers and storms are still
expected. The forecast was updated to increase pops across southern
IN over the next few hours. Cloud cover was also adjusted based on
current trends.

Issued at 818 AM EDT Mon Sep 18 2017

Rain has begun to move into western portions of the forecast area
this morning a bit earlier than previously forecast. Pops were
updated to reflect this and mention the chance for rain earlier in
the day. Otherwise, no changes were made.


.Short Term...(Today through Tuesday)
Issued at 330 AM EDT Mon Sep 18 2017

Upper level ridging that has been in control of our weather for the
past several days is forecast to weaken and move east over the short
term period.  Early morning satellite imagery shows mostly clear
skies over Kentucky with mostly cloudy skies over southern Indiana.
It was still relatively mild across the region this morning with
temperatures generally in the lower to middle 60s.  Some upper 60s
were noted across far western Kentucky where some cloud cover had
moved in.  For the remainder of the overnight period, quiet weather
is expected with temperatures remaining in the lower-mid 60s.

For today and tonight, with upper level ridging sliding eastward and
some lowering of heights coming in from the west, associated surface
front will drop into the region but then stall out.  Model proximity
soundings show some instability developing this afternoon, and most
high resolution models show scattered convection developing.  This
looks to be primarily diurnal in nature, so the convection looks to
peak in the late afternoon and then diminish toward sunset.  The
highest chances of precipitation look to be across our western
areas.  Temperature forecasts will be challenging due to cloud cover
and verification data showing the models have been too cool over the
last few days.  For now, have gone closer to the bias-corrected
blends which keep highs in the 83-88 degree range.  Overnight lows
look to remain mild with mid-upper 60s expected.

For Tuesday, unsettled weather looks more likely here as we`ll have
a noticeable trough axis overhead with a few disturbances moving
through within the mean flow.  Convection looks to be maximized
during the afternoon with a likely 40-50% coverage.  Temperatures
look to remain above normal with highs in the lower-middle 80s.

.Long Term...(Tuesday night through Sunday)
Issued at 345 AM EDT Mon Sep 18 2017

Unsettled weather looks to continue Tuesday night into Wednesday as
upper troughing remains over the region.  Heights may start to rise
a bit by late Wednesday as tropical cyclone Jose heads off to the
northeast and more significant troughing develops across the
western CONUS.  For now, will keep scattered showers and storms in
the forecast for Tuesday night through Wednesday night.  Temps
through the period will remain above normal with daytime highs in
the 80s and lows in the 60s.

For the late week and weekend forecast period, the models are pretty
good agreement with a massive upper level trough developing over the
western United States.   A corresponding downstream ridge will hold
sway across the eastern US which will keep the Ohio Valley area
mainly dry with above normal temperatures.  Even though we`ll see
rising heights through the period, there is still a possibility that
we could see some isolated showers and storms Thursday and Friday
afternoon, though the overall forecast trends continue to show
lesser chances with each successive forecast.  The highly amplified
pattern with a trough in the western US and a ridge in the eastern
US looks to hold through the upcoming weekend, resulting in mainly
dry and warm weather for us.  Daytime highs look to average in the
83-88 degree range with overnight lows in the upper 60s.

Looking beyond into week 2, strong ridging looks to continue into
early next week.  A complex upper level pattern will be in place
during the period which will result in great uncertainty with the
possible effects of tropical cyclones Jose and Maria on the eastern
US coast.  The crux of the forecast will depend how strong and how
the upper level ridge develops in the eastern US and the western
Atlantic.  It does appear that a significant pattern shift will
occur in the middle of week 2 (toward the end of the month) which
will bring a period of unsettled weather followed by a much cooler
pattern setting up as we close out the month and head into October.


.Aviation...(12Z TAF Issuance)
Issued at 644 AM EDT Mon Sep 18 2017

Fog continues to be a concern this morning, mainly at BWG. Expect to
continue to see variations between 4SM and 1/2 SM for another hour
or two before improving. The other TAF sites have stayed VFR,
although still can`t rule out a brief period of MVFR at LEX as they
stay out of the upper sky cover. HNB/SDF are now under the upper sky
cover so expect any additional fog potential to be limited.

Otherwise, a weakening cold front will approach from the northwest
and stall around the Ohio River later today. As a result, scattered
showers and thunderstorms will be possible in the afternoon mainly
at HNB and BWG. Can`t rule out some activity near SDF/LEX but think
the likelihood is for a dry afternoon/evening versus seeing an
isolated storm. Outside of any shower or storm in the afternoon,
expect VFR with Sct cumulus around 4-5 K feet and some upper clouds.
Winds will be light out of the SW.




Short Term...MJ
Long Term....MJ
Aviation...BJS is the U.S. government's official web portal to all federal, state and local government web resources and services.