Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 291656
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
1156 AM EST Tue Nov 29 2016

.Forecast Update...
Issued at 1156 AM EST Tue Nov 29 2016

...Severe Threat for South Central/East Central KY Overnight...

No changes to the forecast at this point. Latest model runs continue
to support the idea of a meso-low track generally along a Bowling
Green to Richmond, KY line overnight. Confidence continues to grow
that this feature will exist, and if so, should be able to bring a
briefly unstable environment along with an enhancement in the low
level wind profile. Given the strong and veering wind fields,
combined with some instability a threat for damaging winds and an
isolated tornado could exist overnight. This would mainly be along
and SE of the line mentioned above. The SPC Slight Risk has the main
threat area depicted well. One minor change to previous thinking is
that the threat could last until 5 or 6 AM EST. The overall window
for severe will likely be shorter than the 9 PM EST - 6 AM EST
window we are given now as storm motion will likely be quite fast.
Will try to narrow this window as we move through the afternoon.

We`ll be playing up the night-time severe weather safety message,
including mention of multiple ways to receive Watch/Warning
information.

&&

.Short Term...(This afternoon through Wednesday evening)
Issued at 255 AM EST Tue Nov 29 2016

...Severe Weather Possible Tonight in South-Central/East-Central
Kentucky...

Weather pattern remains quite progressive with fast SW flow aloft
over the Ohio Valley. Main challenge is the impact and severe
weather potential tonight, as a mid-level disturbance lifts quickly
NE from southeast Texas into the Tennessee Valley.

Convection will break out over the Lower Mississippi Valley this
afternoon, then spread into south central Kentucky this evening.
Shear will be quite strong with a S-SW low-level jet and fast WSW
upper flow, which will make for large curved hodographs. SPC Day 1
outlook extends the slight risk as far north as Bowling Green and
Danville, mainly focusing on an isolated nocturnal tornado threat
peaking in the 03-07Z time frame. The potential is even greater if
the NAM12 solution verifies, with a surface low lifting NE across
central Kentucky to really crank up the 0-1km helicity. Bottom line
is that anyone south of the Western Kentucky or Bluegrass Parkways
should have at least two ways to receive severe weather warnings
tonight.

In general, precip will spread into Kentucky from SW to NE this
evening, and could initially be scattered in nature. Highest POPs
and QPF will be after midnight and closer to the Cumberland
Escarpment, as the precip shield manages to consolidate.

Otherwise expect unseasonably mild temps through the period in the
strong warm advection. Guidance max temps in the 60s look like a
good bet, and min temp forecast is on the high end of guidance as
some parts of south-central KY may be hard pressed to dip below 60
tonight.

&&

.Long Term...(After midnight Wednesday night through Monday)
Issued at 255 AM EST Tue Nov 29 2016

Latter half of the week looks quiet for the Ohio Valley, with zonal
flow aloft, but low-level flow out of the W-NW as high pressure
trying to build in from the west meets resistance from the weakening
low over the Great Lakes. Therefore, while the air mass doesn`t get
that cold, we will continue to deal with at least partial cloud
cover, especially from southern Indiana over into the Bluegrass
region. This will keep temps just a few degrees below climo both day
and night through Saturday.

Saturday night through Monday will be more active again, but
confidence is quite low given wildly diverging model solutions.
There is slight agreement between GFS and ECMWF on precip chances
for Sunday, but beyond that the two models end up completely out of
phase by late Monday. The Euro solution most closely mirrors the
previous forecast, with a fairly long stretch of chance POPs Sat
night through Mon, and very narrow diurnal temp ranges. Leaned
heavily toward the coolest guidance for max temps, and warmer
guidance for min temps, which keeps us just warm enough for an
intermittent cold rain.

&&

.Aviation...(18Z TAF Issuance)
Issued at 615 AM EST Tue Nov 29 2016

Latest IR satellite imagery shows clear skies across middle TN and
central KY while batch of low clouds lies across southwest KY and
southeast MO. Expect VFR conditions through most of today as that
low cloud area stays north/northwest of the TAF sites. South to
southwest winds will mix out to 10-12 kts with some gusts to near 20
kts this afternoon.

A quick moving area of low pressure is forecast to track from middle
TN to south-central KY later this evening and overnight. A shield of
rain and some thunderstorms are likely to move along a BWG to LEX
line, some of those storms could be strong. Strong signals in the
data that MVFR to IFR ceilings will develop around and after 06z
tonight, potentially continuing through 12z or so. Trended the TAFs
more pessimistic with the ceiling forecast, but later updates may
need to lower this more if confidence increases.

&&

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

$$

Update...BJS
Short Term...RAS
Long Term...RAS
Aviation...ZT



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