Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 050244
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
944 PM EST Sun Dec 4 2016

.Forecast Update...
Issued at 925 PM EST Sun Dec 4 2016

Back edge of the rain shield is pushing into eastern Kentucky this
evening, with just a little lingering drizzle or light rain still
extending from the Bluegrass SW to near Lake Cumberland. Webcams
still suggest there is some drizzle farther west of where we are
seeing radar returns. Ceilings are lifting and precip is ending a
bit faster than previously advertised, but as the deeper moisture
exits, trapped low-level moisture will likely allow a stratus build-
down after midnight. Therefore we remain fairly confident in the
mention of fog toward morning, especially in south central and east-
central Kentucky. Hi-res products will be updated to better capture
these trends, but will wait another hour or so for a ZFP update to
handle the ending of precip.

&&

.Short Term...(This evening through Monday night)
Issued at 245 PM EST Sun Dec 4 2016

Upper trough swinging across the Midwest this hour, with an area of
rain falling out ahead of it. A second system is bringing additional
rains over the Appalachians this afternoon. Central KY is in the gap
between the two, but that should fill in the rest of the afternoon.
That trough axis will shift east of the region this evening, with
lingering rains/drizzle possible trailing behind it for a few more
hours.

High pressure will move over our region, being centered near
Louisville by daybreak Monday. Cloud cover should keep us from
getting too cold in the light winds drifting around this high. The
next question is how long cloud cover will linger through the day
Monday. Will go on the pessimistic side, and consequently keep
temperatures a little below normal for highs.

Our brief dry period will end Monday night, as the upper low over
northwest Mexico weakens, but stays a potent little shortwave moving
northeast into the Tennessee Valley by Tuesday morning. This feature
will cause surface low pressure over the northwest Gulf of Mexico
tonight, and this low should travel northeast to western KY by
daybreak. Strong lift ahead of this low, will make for solid rain
chances and even some elevated thunderstorms over at least the
southern half of KY. For rainfall totals, bleeding a little into the
long term period, we look like we`ll average between 0.5 and 1.5
inches by the end of the day Tuesday with the bulk coming early
Tuesday.

.Long Term...(Tuesday through Sunday)
Issued at 245 PM EST Sun Dec 4 2016

That surface low will continue quickly moving northeast into the
Upper Ohio Valley through the day Tuesday. We`ll keep in good rain
chances through the day. How warm it gets will depend on the exact
track of that low, with highs during the day into the mid to upper
50s east of the track, but likely in the upper 40s west of it.

High pressure will ridge into the region from southwest Canada
Wednesday. Then Wednesday night, a larger scale upper trough will
move into the Mid Mississippi Valley. Models show pretty good
agreement (and have for days) for the features in the short term
through Wednesday, but they continue to struggle with what happens
as this trough moves through the Midwest. The ECMWF continues to
show a wetter solution, with a surface low travelling along a cold
front.  The GFS has some QPF in the area, and the GEM is the driest.
The GEFS has a large spread in its MSLP field Wed. night, hinting
that some of its solutions have a low travelling through. The end of
the SREF has a low in its mean field, with again a large spread in
our region.

Thus there is some support for a low to be in the region. Similar to
the Tuesday system, expect warmer temperatures to the right of the
track and colder to the left. That will mean a stripe of rain for
most of the Euro`s QPF field with some tail-end snow on the back
side. The blended forecast had a more deterministic forecast, so had
to back in the rain/snow mix line west of its location. Still some
chance for our first minor accumulations.

After that system, we`ve got some cold air moving in, with
temperatures struggling to reach 30 degrees Friday and lows in the
upper teens and low 20s that morning and the next. Our last system
of the period will get in here Sat. night/Sunday and depending on
timing could bring us another bout of snow.

&&

.Aviation...(00Z TAF Issuance)
Issued at 555 PM EST Sun Dec 4 2016

IFR ceilings and vis with light rain or drizzle figure to remain in
place well into the night. Upper trof axis pushes through this
evening, shifting winds to the west and shunting the deep moisture
out of the area. However, enough low-level moisture will remain
trapped to sustain low clouds and drizzle. This will keep ceiling
and vis down.

Could see some improvement toward daybreak, but not sold on it as
this is the type of scenario where it takes some precip to scour out
the boundary layer, but that is not coming. Will continue IFR
through mid/late morning, when there is a better chance to start
mixing out the low-level moisture. Ceiling and vis should improve to
MVFR but still fuel-alternate.

Expect vis to recover to VFR and low clouds to scatter out in the
afternoon on a slightly drier east wind. BWG could hold on to a VFR
strato-cu ceiling, being closer to the next system coming in.
However, any impacts from that system will hold off beyond even the
SDF planning period.


&&

.LMK Watches/Warnings/Advisories...
IN...None.
KY...None.
&&

$$

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


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