Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 131728
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
128 PM EDT Wed Sep 13 2017

...Updated Aviation Discussion...

...Forecast Update...
Issued at 1055 AM EDT Wed Sep 13 2017

Upper low continues to spin along the lower Ohio River Valley this
morning. Have a band of light to moderate rainfall just north of the
river pivoting around Tell City. Flow becoming more southerly this
afternoon across Central Kentucky should allow for numerous showers
and a cool day.

Side note: BWG may set a record cold max for today. So far they have
made it to 63 on the day, and the record is 66, set last back in
1975. Current forecast calls for it to break that record.

.Short Term (Now through Thursday)...
Issued at 300 AM EDT Wed Sep 13 2017

Short range models move the mid-level low from the TN Valley across
central KY today and then into OH by Thursday morning. Remnant
surface low will meander NNE as well, and continue a slow weakening
trend. Widespread clouds will accompany this system with off and on
rain showers today and tonight.

Currently, scattered light showers are moving rapidly N and NW
across central KY and southern IN. Difficult to pin down where
showers will be most prevalent today given a slow weakening in
forcing fields. Mid-level water vapor imagery suggests a weak
shortwave could be rotating around the S side of the low, which
could enhance showers somewhat over parts of central KY later today.
Conceivably, showers could be most prevalent on the NW and W side of
the upper low, as has been the case, and in developing southerly
flow east of the low. Otherwise, probabilities will be somewhat
generic with scattered to numerous showers today and tonight, with
low precip amounts. Dry weather will occur from time to time as well.

Low clouds will keep temperatures in check for much of the day, with
afternoon highs only in the 60s. Lows tonight will generally be in
the mid and upper 50s.

On Thursday, the low pulls away. Low clouds and scattered light
showers should linger in the morning, but a few breaks in the clouds
could develop in our western counties late in the day. It will be a
little milder on Thursday, with highs in the lower 70s in east-
central KY to the mid-upper 70s in our western counties.

.Long Term (Thursday night through Tuesday)...
Issued at 300 AM EDT Wed Sep 13 2017

The extended forecast period will be highlighted by increasing
heights aloft as a ridge of high pressure builds across the Ohio
Valley this weekend and continues the first half of next week. As a
result, a warming trend will occur during the period with high
temperatures returning to late summer levels in the 80s, i.e., near
or a few degrees above normal. Humidity levels also will rise
(surface dewpoints in the 60s) but should not be oppressive.

Overall, the extended period should be dry. A cold front is forecast
to move southeast into northern MO and central IN on Sunday, but
then weaken or stall as it encounters the ridge aloft over the Ohio
Valley. As a result, most convective activity associated with it
should stay to our north and west. However, isolated storms could
move into or develop over southern IN into parts of central KY on
Monday. The latest ECMWF shows less ridging in our area Monday and
Tuesday, with a little better chance for showers than the GFS and
GEM. Our forecast represents a blend of these possible solutions.

&&

.Aviation (18Z TAF Update)...
Issued at 115 PM EDT Wed Sep 13 2017

Light rain or even drizzle will continue to keep flight categories
restricted this afternoon and through the night. Ceilings will
oscillate between fuel-alternate MVFR and IFR through this evening,
with occasional restrictions to visibilities depending on the rain.
We may even start to see the visibilities improve when the rain
picks up, but that will be difficult to time with any more detail
than a TEMPO group.

Stratus will build down this evening, with solid IFR and even some
LIFR ceilings expected. SDF should be able to avoid the LIFR
through the inbound traffic peak.

As we get to the back side of the remnant low mid-late morning on
Thursday, expect a rapid improvement with ceilings at least lifting
to high-end MVFR. Could even go VFR in the planning period at SDF,
with light/variable winds, perhaps settling into a W-SW direction.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

Update.........RJS
Short Term.....TWF
Long Term......TWF
Aviation.......RAS



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