Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 020323

Area Forecast Discussion
National Weather Service Louisville KY
1023 PM EST TUE DEC 1 2015

...Updated Aviation Discussion...

.SHORT TERM (Now through Wednesday Night)...
Issued at 310 PM EST Tue Dec 1 2015

Anomalous closed upper low is now centered over NW Iowa, with deep
SW flow aloft continuing to stream high level moisture over our
region. This is of little consequence other than upper level clouds,
however as a mid level dry slot has cut off deep moisture. At the
low levels, moisture is being cut off by a surface frontal boundary,
helping to usher in drier air. A few very light showers or drizzle
may linger for a few more hours in the east, but measurable
preciptiation is essentially done. Temps should begin to slowly
dropin the next hour or two as the slightly cooler air advects in,
combating brief breaks in the clouds.

Expecting a complex overnight period as we see intermittent clearing
between waves of high clouds and lingering low level moisture. Given
the recent high rainfall totals and transient favorable radiational
cooling conditions, patches of dense fog are expected into the
overnight. This will be more common across our west and cenral CWA
intially as thick high clouds should remain in the east. As we move
into the pre-dawn hours to around dawn, focus for patchy or areas of
dense fog will shift to areas along and between the I-65 and I-75
corridors, north of the Cumberland Parkway. Will likely see
improvement west and south during this time due to increase surface
winds/warm advection ahead of approaching system. Can`t rule out
that our NE counties could need a Dense Fog headline toward dawn if
everything works out right, however given the complex scenario that
has to unfold confidence is not high enough at this time. Will
mention in ZFP and perhaps HWO. Fog is expected to linger in our NE
through mid morning.

Complex weather setup continues into Wednesday and Wednesday evening
as closed upper low moves into the lower Great Lakes and a couple of
intense shortwaves rotate into our region. A thin layer of low level
moisture will accompany these features as low level lapse rates
steepen dramatically, behind a secondary cold front. Warm advection
early should help temps warm to the mid and upper 40s in many spots,
with low 50s east. This will be warm enough to promote rain showers
ahead of the initial vort lobes rotating through in the late morning
and afternoon. Freezing levels will likely be low enough to support
some graupel or very small ice pellets given the steep low level
lapse rates. Expecting wind gusts could be in the 25 to 35 mph range
tomorrow with the frontal passage.

As we head into the evening and overnight, surface temps will fall
through the mid 30s and into the lower 30s. Meanwhile, a 2-3 k foot
low level cloud deck should be saturating up into air as cold as -6
to -9 C. This is not optimial for ice crystals, but is sufficient
for at least some so will include mention of a slight chance of
light snow showers or flurries where surface temps are less than 36
degrees. Sprinkles or drizzle will likely mix in as well. This
covers areas mainly along and north of the I-64 corridor. Not
expecting any accumulations, but some flakes could fly so wanted
everyone to be aware. Suppose a brief dusting on a roof top could
occur in our NE given the strong forcing, low level lapse rates, and
deeper moisture into the colder air. Hi-res models (ARW/NMM) are
quite bullish with some of the QPF fields, but are likely a little
overdone given the very shallow moisture layer. South of I-64,
expect mainly sprinkles or a few flurries. Temps will be around 30
by dawn on Thursday.

.LONG TERM (Thursday through Tuesday)...
Issued at 310 PM EST Tue Dec 1 2015

Thursday - Sunday Night...

Trough moves off to the east to end the week, as a
progressiveupperridge begins to take hold of the region. Meanwhile,
surfacehighpressure will dominate. This pattern will persist
throughtheweekend bring dry and mainly seasonal temperatures. We
will be abitchilly on Thursday as the mercury doesn`t make it out of
the midandupper 40s. We`ll warm into the upper 40s and low 50s by
Friday.Hightemps will then be above normal in the mid 50s as we
moveintoSat/Sun. Expect chilly overnight lows in the 20s and
low30sThursday and Friday nights. We`ll be mostly in the low and
mid30sSaturday and Sunday nights.

Sunday Night - Tuesday...

Upper ridge axis moves east on Sunday, allowing for some
variationofa closed upper low to move near our region to start the
newworkweek. Models continue to struggle with this system so
confidenceislow. Will stay optimisitic with low chances for rain
duringthistime as a lot of data takes the system south of us.
However,somepops are warranted. Monday/Monday Night into early
Tuesday.Tempswill be depenent on this system, but overall ranges
nearnomrals arereasonable for now.


.AVIATION (00Z TAF Update)...
Updated at 612 PM EST Tue Dec 1 2015

Ceilings and visibilities are a challenge tonight as multiple
factors could play into the formation of low clouds and/or fog.
Mainly high clouds remain in place across SDF and BWG with a few to
scattered lower ones. If clouds can clear out there is enough low
level moisture that some fog and/or a low stratus deck could form,
particularly at BWG. However, not sure we will get the clearing
early enough before winds begin to pick up early tomorrow morning.
Guidance is less pessimistic in ceilings and visibilities at BWG
than in previous runs, so kept them a bit higher than in the previous
forecast. LEX on the other hand stands a better chance for low
cigs/vsbys tonight, so will lower the forecast. Some dense fog is
not out of the question, but confidence is low so will keep things
in the IFR range.

Winds will pick up out of the southwest through the morning tomorrow
and become gusty by mid day. VFR cu looks to develop in the


.LMK Watches/Warnings/Advisories...


Short Term........BJS
Long Term.........BJS
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