Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 210130

Area Forecast Discussion
National Weather Service Louisville KY
930 PM EDT Fri Oct 20 2017

.Forecast Update...
Issued at 929 PM EDT Fri Oct 20 2017

Cirrus is streaming across the region from the south this evening.
Given some denser patches of cirrus, cloud cover was increased a bit
overnight. The other change made this evening was to add patchy fog
into the grids for the river valleys. Guidance continues to suggest
some fog will form in these locations despite the increasing winds
aloft. Updates have already been sent.


.Short Term...(This evening through Saturday night)
Issued at 305 PM EDT Fri Oct 20 2017

Warm and dry conditions are expected to continue through the short
term period.  Skies were mostly clear this afternoon other than some
light cirrus blowing in from the west.  Afternoon temperatures were
in the lower to middle 70s and highs should top out in the next hour
or so before falling into the 60s for the evening hours.  Clear
skies are expected overnight.  Fog potential still looks rather
limited given that winds aloft will be increasing leading to a
turbulent PBL top which should result in better mixing. Nonetheless,
some river/valley fog will still may form in some spots.  Lows
tonight will drop into the upper 40s to the lower 50s.

For Saturday, mostly sunny conditions are expected.  Highs should
average a little warmer than today with highs in the 73-78 degree
range.  Clouds will be on the increase from the west Saturday night.
Lows look to cool into the upper 50s in the west to the upper
40s/lower 50s in the I-75/Bluegrass corridor.

.Long Term...(Sunday through Friday)
Issued at 327 PM EDT Fri Oct 20 2017

High pressure will move off to the east late Saturday night and
early Sunday as a sharp upper level trough axis pushes through the
Plains.  Moisture flow will continue into the region on Sunday and
mostly cloudy skies are expected.  Overall model solutions are still
slightly slower with the cold front pushing in from the west.  First
half of the day looks to be mainly dry, with precipitation
increasing from west to east through the afternoon and into the
evening hours.  We`ll see one more warm day with highs topping out
in the mid-upper 70s before the front pushes through the region.

By Sunday night, model solutions continue to take the sharpening
trough and letting the southern edge cut off over the southern Mid-
Mississippi Valley.  This low should continue to deepen and slowly
migrate toward the region late Sunday night and into the day on
Monday.  Widespread rainfall, moderate to heavy at times, will be
seen from Sunday night through Monday night.  For this forecast,
plan on carrying high PoPs throughout the period.  Another soaking
rainfall is expected with a solid 1-2 inches of rainfall expected
before precipitation diminishes in intensity Monday night.  Lows
Sunday night will cool into the upper 50s with highs on Monday
topping out in the 60s.  Temperatures look to cool into the upper
40s to around 50 by Tuesday morning.

By Tuesday, upper level low will lift off to the northeast and a
larger gyre will develop over the Great Lakes.  A very deep long
wave trough axis will slowly push through the region on Tuesday into
Wednesday.  With colder air aloft, we`ll probably see some continued
lingering precipitation Tuesday and diminishing on Wednesday.  Below
normal temperatures are expected for Tuesday and Wednesday.  Highs
Tuesday will only warm into the 50s with lows around 40 or so. Highs
Wednesday will likely exhibit a range from the upper 40s to the
lower 50s.  Lows Wednesday night will cool into the mid-upper 30s.
This could result in another frost threat, especially if skies clear
out a little faster than forecast.

For Thursday and Friday, the pattern will quickly relax and revert
back to a southwesterly flow over the eastern US.  This should
result in a drier and slightly milder pattern developing for
Thursday and Friday.  Highs both days will warm back into the upper
50s to the lower 60s with overnight lows mainly in the 40s.

As we move into the next weekend, majority of the global guidance
strong suggests a very deep trough axis developing across the
central Plains.  This is a teleconnective response to the expected
recurving Typhoon Lan over the western Pacific from earlier in the
extended period.  This trough axis is expected to impact the Ohio
Valley by the early weekend, sending a surging cold front into the
region.  Convection, some possibly strong, will accompany this front
as it pushes through.  Instability and storm intensity will likely
depend on timing of the front.  Euro and its ensembles are slower
than the more progressive GFS solutions.  Given the usual speed
biases of the numerical guidance at day 7-8, the slower solution is
preferred here.  Nonetheless, much colder air is expected to pour
into the region behind the front with a possible widespread
frost/freeze occurring by Sunday or possibly Monday morning.

While temps will run below normal next weekend and towards
Halloween, the lack of significant blocking will allow the pattern
to relax and milder temperatures are likely to return to the region
as we enter November.  However, that mildness is not expected to
last long as an active weather pattern is expected to continue with
experimental signal guidance suggesting another round of cold
returning around the time we fall back on 11/5.


.Aviation...(00Z TAF Issuance)
Issued at 655 PM EDT Fri Oct 20 2017

High pressure will slowly shift eastward during this TAF period, but
will still exert its influence over the region. VFR conditions are
expected through tomorrow. Winds aloft tonight will be stronger than
the last few nights, so not much fog is expected to develop. Winds
will be light out of the south to southeast tonight. They will
increase to 8-11 knots sustained tomorrow. Some gusts of 15-18
knots will be possible in the afternoon, particularly at HNB.




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