Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 151539

Area Forecast Discussion
National Weather Service Louisville KY
1039 AM EST Wed Nov 15 2017

.Forecast Update...
Issued at 1038 AM EST Tue Nov 15 2017

Surface cold front remains out to the west of the region and is
moving eastward. First band of precipitation is working east into
the I-65 corridor with large shield of rainfall out across southwest
IN and NW KY.  This activity will continue to push eastward so a
rather rainy afternoon is on tap for areas west of I-65.  Further
east toward the I-75 corridor, partly sunny skies were noted and are
expected for the next few hours.  Clouds will increase throughout
the day with precipitation arriving in the mid-late afternoon hours.

Current forecast remains largely on track.  Just did some minor
edits to the elements to bring closer in line with observations.
Highs out west will top out in the lower 50s, but areas out toward
the I-75 corridor may warm into the mid-upper 50s before the rain
moves in.


.Short Term...(Today through Thursday)
Issued at 255 AM EST Wed Nov 15 2017

Main player today is a progressive upper trof over the Upper
Midwest, and a cold front currently trailing along the I-35 corridor
from Minnesota to Kansas. Ahead of this feature, southerly flow is
establishing a decent moisture feed up the mid Mississippi Valley
that has yet to get much precip to the ground.

Expect precip to blossom ahead of the cold front in the next few
hrs, with numerous showers spreading eastward to reach the I-65
corridor by midday and the Bluegrass and Lake Cumberland early to
mid afternoon. QPF looks to be around a quarter inch before rain
departs in the late afternoon and evening hours.

Quiet weather and below normal temps will follow late Wednesday
night and Thursday as high pressure builds through the Great Lakes.
Even with shortwave ridging aloft, it`s a shallow cold air mass and
temps will struggle to crack 50 on Thursday afternoon.

.Long Term...(Thursday night through Tuesday)
Issued at 255 AM EST Wed Nov 15 2017

Thursday night/Friday morning look to the coldest of this work week
as the surface ridge axis will be oriented roughly along I-75.
Transitional day on Friday as the high departs and a strong warm
advection regime sets up ahead of a complex storm system taking
shape over the Plains.

Biggest challenge with this system is timing, and the main impact
will be wind. Latest solutions are starting to converge on a
Saturday fropa, but still a solid 6 to maybe 12 hrs difference
between the GFS and ECMWF. This forecast will include categorical
rain chances on Saturday, and a non-diurnal temp curve Friday night
in the pre-frontal warm advection. Wind still appears to be a good
bet ahead of the front, as well as behind the front, with low-level
wind fields still supporting 30-40 mph gusts.

This system still bears watching for severe potential as the
environment will be very dynamic and strongly sheared. A slower
fropa on Saturday could open a narrow window for instability ahead
of the front to support severe storms, but at this point it still
appears unlikely that we will have either CAPE or pre-frontal storms
to become surface-based.

Once the cold front and associated precipitation clear the region,
we should remain dry for the remainder of the long term period. Long
range guidance still in some disagreement in regards to pattern next
week, but the general consensus is that below normal temperatures
can be expected.


.Aviation...(12Z TAF Issuance)
Issued at 545 AM EST Wed Nov 15 2017

Plan on VFR conditions through mid-morning but deteriorating
conditions afterward as a cold front brings low ceilings, widespread
rainfall, and reduced visibility to the region. Showers are expected
to move across the area between 15-18z, with the highest coverage of
low ceilings and reduced visibility later this morning into the
afternoon hours. Expect at least fuel-alternate MVFR ceilings with
high probabilities of IFR ceilings at all sites. Some improvement is
expected later this evening as westerly winds dry out the low
levels. It may take some time to completely scour out the low level
moisture at LEX however.

Winds ahead of the front will become gusty out of the southwest near
20 kts later this morning. Expect a wind shift to the west as the
front passes with sustained winds 8-12 kts.




Short Term...RAS
Long Term....RAS
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