NWS Area Weather Forecast Discussion
Louisville, KY

FXUS63 KLMK 192320

Area Forecast Discussion
National Weather Service Louisville KY
720 PM EDT Fri Oct 19 2018

.Short Term...(This evening through Saturday)
Issued at 243 PM EDT Fri Oct 19 2018

...Gusty Winds With Cold Frontal Passage Tomorrow Afternoon And

Regional radars reveal a band of showers stretching from TX into the
Great Lakes region ahead of a pre-frontal trough. Obs across western
KY and southern Indiana are already reporting rain, and expect that
rain to move quickly into western parts of the region over the next
couple of hours before covering the entire area tonight.

The rain showers with the pre-frontal trough look to be mostly out
of the region by sunrise Saturday morning, with the exception of
locations across eastern KY and near the TN border where showers
could linger into the late morning hours. Models indicate clouds
slowly clearing in areas along and west of I-65, though forecast
soundings show some moisture potentially trapped near the top of the
boundary layer, so confidence in this clearing remains low.

The bigger story tomorrow will be the winds. A strong cold front
will swing through late in the afternoon, and model soundings
indicate very deep mixing and gusty (40-50kt) winds near the top of
the boundary layer with the fropa due to a strong post-frontal
surface high tightening the pressure gradient. With fropa occurring
so late in the day, there will be a small window for 40+ mph
surface wind gusts before the boundary layer stabilizes enough in
the evening hours to keep gusts under 40mph. The best chance for
these strong winds will generally be across southern Indiana and
northern Kentucky. After collaborating with surrounding offices,
will hold off on the issuance of a wind advisory for the moment,
but if conditions continue to look favorable for strong wind
gusts, then a wind advisory may be needed in subsequent forecast

.Long Term...(Saturday night through Friday)
Issued at 255 PM EDT Fri Oct 19 2018

We start off this period with a secondary cold front crossing into
Eastern Kentucky. The pressure gradient associated with this frontal
passage is fairly tight, and the response will be gusty west to
northwest winds through the evening hours. The high pressure
building in behind this front looks to become centered over the
Commonwealth by Sunday afternoon and then into the Appalachians by
Monday morning. Still think the proximity of the high center will
make for light and variable winds through the night and subsequent
good conditions for frost development. Lows should be similar to
Sunday morning, but the calmer winds should make for more widespread
frost development. Taking a quick look at any potential cloud layers
that could affect temperatures, the GFS does show increased RH
values in the 300-500 mb layer come in from a system to our west
Monday morning. Will have to watch this system to see if any
adjustments are needed to Monday morning lows.

Tuesday we are still on tap for a brief warmup, though a reinforcing
dry cold front should clip through here in the afternoon/evening
hours. That front should keep our temperatures below normal for
Wednesday. After that models diverge a bit on whether a southern
stream system affects us. The 00Z Euro had some rain chances both
Thursday and Friday, whereas the GFS keeps us dry. The 12Z Euro came
in drier for Thursday but still has some rain Friday. Looking at the
12Z GEFS, there is a hint of a wave coming through the Mid MS Valley
but the QPF stays to our south. The European statistical guidance
has been doing well of late, with fairly reliable percentages, and
the 00Z version called for 40-60 pops between the days. SuperBlend
gives a value roughly between the GFS stat guidance and the Euro so
decided not to stray too far from what it came up with.


.Aviation...(00Z TAF Issuance)
Issued at 720 PM EDT Fri Oct 19 2018

An upper trough swinging through the region will bring a variety of
weather to the TAF sites during this forecast package time frame.
Corridor of showers at press time will slowly push off to the east
this evening, but low ceilings will move in and lower to IFR. That
moisture will get trapped and persist into Saturday morning before
lifting and breaking in the afternoon.

Of potentially greater concern tomorrow will be strong and gusty
winds coming in from the WNW as we sit in a tight pressure gradient
between low pressure to our northeast and Canadian high pressure to
our northwest and strong winds aloft come sweeping in from the




Short Term...DM
Long Term...RJS

Forecast Discussion from:
Script developed by: El Dorado Weather
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