Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 181015

Area Forecast Discussion
National Weather Service Louisville KY
615 AM EDT Sat Mar 18 2017

.Forecast Update...
Issued at 615 AM EDT Sat Mar 18 2017

Drier air continues to advect into the region from the northwest.
This has led to a rapid improvement in visibilities across southern
Indiana and the Dense Fog Advisory has been cancelled for that area.
However, dense fog continues to expand eastward into central
Kentucky.  Thus, we have expanded the Dense Fog Advisory eastward to
cover this area for the next few hours.


.Short Term...(Today through Sunday)
Issued at 320 AM EDT Sat Mar 18 2017

Partly to mostly cloudy skies were noted across the region this
morning.  Surface observations revealed widespread dense fog
generally along and west of the I-65 corridor.  A Dense Fog Advisory
was posted earlier for this region.  Will continue to watch
visibilities this morning in areas east of I-65 and if visibilities
drop, the advisory may need to be expanded eastward.  Temperatures
were generally in the upper 40s to the lower 50s across the region.
In the near term, we expect see temps drop a little more to their
minimums before warming after sunrise.

For today, closed upper level low will work southeastward out of the
Great Lakes and head into the Mid-Atlantic region.  A deep
northwesterly flow will persist through the Ohio Valley.  A gradient
of cloud cover and temperatures are expected.  Partly to mostly
cloudy skies will be found across the northeastern sections with
cooler temps, while more sunshine and warmer temps will be found
over the southwestern sections.  Highs will generally warm into the
mid-upper 40s over our far northeast sections with lower-mid 50s
over our southwest sections.

Drier air is expected to work in from the northwest later this
evening and overnight resulting in mostly clear skies with lows
dropping into the lower 30s in most areas.  High pressure will pass
over the region on Sunday resulting in mostly sunny skies with highs
ranging from the lower 50s over the Bluegrass region to the mid-
upper 50s across the southwestern sections.

.Long Term...(Sunday night through Friday)
Issued at 337 AM EDT Sat Mar 18 2017

Sunday night through Tuesday Night...

Upper level ridging is expected to move eastward across the Sunday
night.  However, a small mid-level trough axis looks to move in from
the Midwest overnight coincident with an approaching warm frontal
boundary.  Model proximity soundings show a decent low-level
temperature inversion with sharp mid-level lapse rates aloft
revealing plenty of elevated instability.  Models suggest that we`ll
see some shower and thunderstorm activity ahead of this feature.
Thus, have added thunder in the forecast for late Sunday and early
Monday.  We`ll get warm sectored on Monday before a cold front
pushes through the region bringing another round of showers and
thunderstorms to the region.  The front looks to be a slow mover
here given that the flow aloft will be somewhat parallel to the
surface flow.  Thus, showers and storms will likely linger well into
Tuesday before diminishing Tuesday night.  In general, we have
increased PoPs through this time frame.

Highs on Monday will be above seasonal normals with readings solidly
in the 60s, through a few of our southwestern locations (Bowling
Green area) could top the lower 70s.  Clouds and precipitation will
keep temps down on Tuesday with readings generally in the upper 50s
to around 60.  Lows through the period look to be in the 40s.

Wednesday through Friday...

The latest data suggests that the frontal boundary will get a decent
push southward and it should clear our region by Wednesday morning.
So it appears that Wednesday and Wednesday night will be dry and
quiet.  Highs Wednesday will remain in the lower-mid 50s with
overnight lows in the 30s.

The front will eventually lift back to the north on Thursday in the
form of a warm front.  The overall evolution of this forecast is a
bit slower than the previous one.  Some scattered showers and
possibly a few thunderstorms will be possible out ahead of the warm
front as it lifts through the region.  A short period of ridging
will then move into the region Thursday night and Friday keeping the
area warm and dry.  However, strong upper level trough axis and
surface cold front will move in from the west late Friday and into
Saturday yielding another round of showers and thunderstorms to the
region.  This system will have to be watched carefully as there are
signals in the data suggesting that strong to severe thunderstorms
may accompany this system as it passes through.


.Aviation...(06Z TAF Issuance)
Issued at 140 AM EDT Sat Mar 18 2017

A cold front was moving southeast across IN and southern IL at this
time, and will move across the TAF sites around or after 12z this
morning. In the meantime, fog has become a problem in areas where
low clouds have cleared or partially cleared ahead of the front,
reducing visibilities to a half or quarter mile in some areas,
including EVV and HNB at this time. High resolution models suggest
this fog axis will move southeast across the TAF sites overnight/
early this morning before clearing southeast with passage of the
front. As a result, have started vsbys at current higher
observational levels, but reduced to one mile or half mile for now
at the 3 TAF sites for a few hours.

After frontal passage at or after 12Z, vsbys should improve quickly
to VFR levels and low clouds will clear out. However, with a cool
somewhat moist northwest low-level flow behind the front, an area of
lower clouds around 3 kft (MVFR) should rotate southeast and affect
SDF and LEX, and to a lessor degree BWG starting late this morning
and afternoon. The clouds should begin to clear late tonight, but
could hold in at LEX. Surface winds will become gusty northwest
today, and subside tonight as surface high pressure moves in from
the west.


KY...Dense Fog Advisory until 9 AM EDT /8 AM CDT/ this morning for



Short Term...MJ
Long Term....MJ
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