Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 212333

Area Forecast Discussion
National Weather Service Louisville KY
733 PM EDT Mon Oct 21 2019

...Updated Aviation Discussion...

.Short Term...(This evening through Tuesday)
Updated at 319 PM EDT Mon Oct 21 2019

Afternoon satellite imagery shows mostly cloudy skies in areas west
of US 27/127.  To the east of US 27/127, partly sunny skies were
noted.  As expected, a gradient of temperature was noted across the
region due to the cloud cover.  Out in the sun, temperatures had
warmed into the 75-80 degree range.  Back under the clouds,
temperatures were generally in the 68-70 degree range.  While the
radar imagery is filled with low returns, we are seeing some areas
of light rain and drizzle.  The heaviest rainfall was still down in
northern TN across Sumner and Macon counties.  This activity will
work northeastward into south-central KY over the next few hours.

Latest round of CAM guidance still insists that some additional
convective development will occur this afternoon.  Current thinking
is that activity over northern TN moving into S/C KY would have the
best chance at upward growth.  Severe weather looks rather unlikely
given the weak instability, and marginal lapse rates.  However, the
environmental shear is still high aloft, which could mix down within
stronger storms promoting an isolated damaging wind gust here or
there.  Further to the west, west of I-65, combination of cloud
cover and weak lapse rates will likely keep instability very low.
There is a chance that we could get some additional development
along the frontal interface, however, forecast confidence on that has
lowered compared to this morning.  Overall, have trimmed PoPs back a
bit for the remainder of the afternoon and evening hours.  Gradient
winds will still be a problem this afternoon and evening.  The
highest wind gusts will likely be confined to the Bluegrass region
where gusts to 40 MPH will be seen at times.  Within the cloud cover
to the west, wind gusts should be more limited with 30-35 MPH
expected through at least sunset.

Surface cold front to the west will push through the region this
evening bringing an end to the threat of showers and storms.
Clearing line just west of KY should work eastward this evening our
skies should clear out after midnight.  Late night stargazers should
have decent viewing conditions of the Orionid Meteor shower which
peaks overnight.  Lows tonight should cool into the mid-upper 40s.

For Tuesday, surface and closed upper level low are expected to be
located over Wisconsin.  This feature is expected to pull slowly
north-northeastward into southern Ontario.  The upper trough axis
will swing through the region bringing a period of stratocumulus to
the region along with gusty west to west-northerly winds.  Wind
gusts on Tuesday will likely top out in the 25-30 MPH range.  Highs
will be cool with readings in the lower 60s.

.Long Term...(Tuesday night through Monday)
Updated at 300 PM EDT Mon Oct 21 2019

Tuesday Night - Thursday...

Surface high pressure centered over the southeastern CONUS will
begin to build into the region Tuesday night and then push off to
the east by Thursday. Expect mostly clear skies throughout this
period with temperatures at or slightly below normal. Low temps
Tuesday night will be in the upper 30s to low 40s and will then warm
slightly Wednesday night into the mid 40s. High temps on Wednesday
and Thursday will be in the mid to upper 60s, with some areas
reaching 70 on Thursday.

Thursday Night - Monday...

Models begin to diverge by the end of the week as an upper level
trough digs east across the Plains. There is a fair amount of
agreement that a cold front will push across the area Thursday
evening into Friday afternoon, with high temps on Friday in the
upper 50s to low 60s and low temps dropping into the upper 30s
Friday night. Concerning precipitation, the GFS continues to be more
of an outlier, suggesting a more progressive trough, with chances of
precipitation moving through the area Friday morning into the
afternoon in association with the front. However, the ECMWF/CMC have
been persistent in developing a closed upper low over the TX
panhandle Friday and then slowly ejecting it northeastward into the
OH Valley by Sunday. This solution would keep us dry through
Saturday before bringing widespread rainfall to the area Saturday
night through Sunday.


.Aviation...(00Z TAF Issuance)
Issued at 730 PM EDT Mon Oct 21 2019

Surface cold front out over Illinois this evening will move east
through the region by late evening.  Rains ahead of this front have
already cleared most of the TAF sites and will be clear of LEX in
about 1-2 hrs.  A brief period of MVFR cigs will follow the rains
ahead of the fropa.  By 6Z, the front should be east of the area
with skies clearing throughout the overnight period.  Winds will
shift to the WSW behind the front.  Another gusty day is expected
for Tues with wind gusts in the 20-24 kt range likely from mid
morning through the afternoon hours.




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