Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 160454

Area Forecast Discussion
National Weather Service Louisville KY
1154 PM EST Sun Jan 15 2017

.Forecast Update...
Issued at 1135 PM EST Sun Jan 15 2017

Have enough webcams down along our border with TN to issue a narrow
Dense Fog Advisory, after coordination with our neighbors.
May have to expand it as the night goes on, but still think a
secondary axis will develop from Hartford to Lexington with a narrow
gap in between. Look for updates overnight.

Issued at 840 PM EST Sun Jan 15 2017

Did a zone update to lessen rain chances the rest of the night and
for an update on fog potential. Still not certain on any particular
area with the best chance for widespread dense fog overnight, and no
sites are showing it at this point. Model trends are for the poorest
visibilities just before daybreak along a Hartford to Lexington
line, with some potential for it to lift northward during the
morning hours. In fact, the CONSShort model, a blend of several high-
res short-term models, has vsby at less than a mile, an indication
of unity in the models, as any one model with higher values would
raise that value a bit. That model shows the lifting north of the
worst values, keeping them at a mile or less through the morning
hours. Have trended the forecast that way for now.

Issued at 635 PM EST Sun Jan 15 2017

Model time-height sections indicate some mid-level dry air working
into the region this hour, and this area is forecast to stick around
through daybreak Monday. That should mean a gradual decline in the
current drizzle but a return to some patches of dense fog, as either
current low-cloud decks may be able to build down through the night
or breaks in the cloud cover allow ground fog to form. Either way we
will have to watch for fog formation through the night and will
issue a special weather statement to highlight the threat.


.Short Term (Now through Monday Night)...
Issued at 320 AM EST Sun Jan 15 2017

Numerous light rain showers are sliding along and north of I-64,
with scattered showers across central KY. These will continue to
slide east through the afternoon and evening as a mid level
disturbance moves through the zonal flow aloft. Most spots along and
north of I-64 should expect around a tenth of an inch through
Midnight or so. A large temp gradient exists across the region with
upper 30s north, to near 50 south. These temps should stay pretty
similar through tonight, with lows mirroring our current temps. The
overall stagnant low level flow combined with trapped low level
moisture should continue to result in patchy fog through the

Upper ridge axis slides over our region by Monday, helping to lift
the warm front north of our region. The morning will likely start
off dry, however isentropic lift picks up through the afternoon
ahead of storm system moving out of the eastern Plains. Best chances
by afternoon will be west of I-65. With the warm front lifting
north, expect mid 60s south, with upper 50s to around 60 north for

Deeper moisture and better forcing arrive Monday night as the
shortwave trough and associated surface low move across the lower
Great Lakes. Some elevated instability will accompany the deep
moisture plume so will include a slight chance of thunder to go along
with widespread rain chances. Temps won`t drop off much on Monday
night ahead of the approaching cold front. Look for mid to upper 50s
for highs.

.Long Term (Tuesday through Sunday)...
Issued at 320 PM EST Sun Jan 15 2017

Tuesday through Wednesday Morning...

Widespread showers, and a few thunderstorms push east through the
region ahead of a cold front on Tuesday. Highs should range in the
low to mid 60s. Most spots should pick up between a half and three
quarters of an inch of rain by the time precipitation winds down
early Tuesday evening.

Can`t completely go with a dry forecast Tuesday night into Wednesday
morning as a secondary shortwave trough axis looks to swing through.
That being said, these periods should be mostly dry with best
chances for an isolated shower across our far south or eastern CWA.
Lows Tuesday night should drop into the upper 30s and low 40s in
most spots.

Wednesday Afternoon - Thursday...

This is expected to be a mainly dry stretch of weather as amplified
upper ridging develops over us in response to upstream overall
troughing. Afternoon highs on Wednesday will be cooler than previous
days, but still well above normal in the 50 to 55 degree range.
After Wednesday night lows in the upper 30s and low 40s, highs
Thursday jump to the 55 to 60 degree range. Will bring in low
chances for rain later Thursday if fast solution offered by 12z
ECMWF/GFS Ensemble mean pans out. More on this storm system below...

Thursday Night - Sunday...

Models diverge Thursday night through the weekend as a complex upper
pattern takes hold. At this point, there looks to be a decent signal
for widespread rainfall sometime in the later Thursday through later
Friday time frame as a moisture rich system ejects out of the Rio
Grande and south Plains. After a potentially dry stretch later Friday
night into Saturday, another round of rainfall could occur Saturday
night into Sunday.

Overall, this should be a continued mild stretch with highs in the
upper 50s and low 60s. Lows should mostly be in the upper 40s.


.Aviation...(06Z TAF Issuance)
Updated at 1155 PM EST Sun Jan 15 2017

IFR ceilings remain well entrenched, and have even lowered to LIFR
at BWG and LEX. Expect to maintain status quo overnight, and if
anything we will just see visibilities get worse as the stratus
builds down. Have included at least TEMPO groups for vis as low as 1
mile, and even a few hrs of prevailing IFR vis monday morning.

Warm front will lift through Kentucky midday-early afternoon on
Monday, with cig/vis finally improving to VFR (if only just barely)
by late afternoon/early evening. Winds come around to the south with
the frontal passage, and will stay up just above the 6 kt threshold
for most of the night.

Isentropic lift in the warm advection brings precip back into the
picture fairly quickly, with VCSH mentions in the evening and even
prevailing SHRA at SDF overnight. However, expect MVFR at worst in
the rain. Can`t rule out thunder, but it`s still a low probability
even at SDF.


KY...Dense Fog Advisory until 9 AM CST Monday for KYZ070-072-073-075.



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