Area Forecast Discussion
Issued by NWS Louisville, KY

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975
FXUS63 KLMK 141903
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
303 PM EDT Sat Oct 14 2017

.Short Term...(This evening through Sunday night)
Issued at 247 PM EDT Sat Oct 14 2017

Current satellite/surface observations reveal a surge of low level
moisture across southern KY where dewpoints are currently in the
upper 60s to low 70s and a strato-cu field remains present. This is
all in response to a 1026mb high currently sitting over the
Carolinas while a 1004mb low sits over the central Plains, and flow
between the two systems is pulling in moisture from the Gulf of
Mexico.

A 45kt LLJ will develop overnight as a strong cold front approaches
from the west. While an inversion will develop, winds will still be
breezy at the surface, generally 10mph-15mph out of the southwest.
Overnight lows will be quite warm thanks to breezy winds and high
dewpoints, with areas west of I-65 staying near the 70 degree mark,
while east of I-65 lows will only fall into the mid and upper 60s.

A decaying line of convection will approach western portions of the
CWA by daybreak ahead of the cold front. Instability will be very
limited through the morning hours due to weak mid-level lapse rates
and cloud cover, so expect most of the precipitation to remain
lightning free. Additionally, QPF looks to be light at this time,
generally around or under a tenth of an inch. The cold front will
slice through the CWA during the day tomorrow, and temperatures will
fall considerably behind the front. For example, the 12z GFS has
temperatures at SDF tomorrow around the mid 70s at 11am, but falling
to the upper 50s by 5pm behind the cold front. Winds will be quite
gusty as well. Combination of strong CAA, pressure rises behind
front, and steep low level lapse rates will result in gusty 25mph-
30mph northwest winds tomorrow morning and afternoon.

Strong CAA will continue into tomorrow night as temperatures
continue to fall. Pressure gradient over region will begin to relax
after midnight, so should see winds lighten up a bit. Overnight lows
will generally be in the low to mid 40s.

&&

.Long Term...(Monday through Saturday)
Issued at 258 PM EDT Sat Oct 14 2017

Surface high pressure will continue to build into the area behind
the cold front Monday with dry NW flow aloft. Monday will be the
coolest day of the week as the bulk of the cold air settles over the
region. Surface high will nearly be on top of the area Monday night,
and with light winds and clear skies, temperatures should bottom out
into the upper 30s to low 40s. A few of the sheltered, colder spots
in the CWA may even see some patchy frost by Tuesday morning.

Flow aloft will then transition into a quasi-zonal to upper ridging
pattern for the mid to late week period. This will result in a
gradual warming trend, and with no significant shortwaves embedded
within the flow, we should remain dry through this period.

&&

.Aviation...(18Z TAF Issuance)
Issued at 200 PM EDT Sat Oct 14 2017

A SCT/BKN MVFR deck continues to push northeast across southern and
eastern KY. The northern extent of these clouds currently runs from
BWG to LEX. BWG had a couple hours with a BKN MVFR deck earlier this
morning, but these clouds shouldn`t result in meaningful aviation
impacts. Prevailing VFR conditions are likely this afternoon through
the overnight period.

SSW winds have increased this afternoon as low pressure deepens over
the Plains. This low pressure system will continue to strengthen as
it tracks northeast through Wisconsin tonight. By 03-06z tonight, a
low level jet of 40-45 kts is expected to develop within 1500-2000
ft above ground out of the southwest. However, LLWS is marginal
since stronger surface flow will be in place as well. Expect a
15-20 degree wind shift between the surface and 2 kft. The strong
SW LLJ will continue through mid-morning Sunday.

After 12z Sunday, expect surface winds to increase further to 10-15
kts with gusts to 20-25 kts. The surface cold front will push
through all four TAF sites during the morning and early afternoon
hours. Expect prevailing light to moderate showery weather with
perhaps a rumble of thunder with the frontal passage.

&&

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

$$

Short Term...DM
Long Term...DM
Aviation...EBW



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