Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 202307

Area Forecast Discussion
National Weather Service Louisville KY
607 PM EST Fri Jan 20 2017

.Short Term...(This evening through Saturday night)
Issued at 300 PM EST Fri Jan 20 2017

Surface warm front has surged through the region this afternoon.
Some partial clearing has allowed some of the area to see some
sunshine which has been absent for a while around here. Temperatures
ranged from the lower 60s in the cloud covered areas to the mid and
upper 60s in the sunshine.  In the near term, we expect partly to
mostly cloudy skies with temperatures remaining in the 60s this
afternoon and cooling off into the 50s this evening.

For tonight, dry conditions are expected with lows cooling into the
50-55 degree range which is 10-15 degrees warmer than our normal
highs for late January.  Some patchy fog will be possible, but
widespread fog looks unlikely due to surface winds remaining slightly
elevated which should keep the lower atmosphere well mixed.

As we head into Saturday, a broad southwest flow at the surface and
aloft will continue across the region.  Some weak mid-level
perturbations will move through within the flow and may kick off a
some showers and thunderstorms mainly across southern Kentucky.
While there is some instability, steepening lapse rates, and some
component of isentropic lift, moisture quality/quantity is a real
issue.  Many of the high resolution convection allowing models show
robust convection to our south.  This may result in a decent
reduction of northward moisture transport out of the Gulf states,
limiting the areal coverage of precipitation Saturday afternoon.

By Saturday night, approaching mid-level wave should result in more
dynamical lifting to support better coverage of
convection...especially across our southwest sections with more
widespread shower and thunderstorms overspreading the region late
Saturday night.

Temperatures Saturday will be quite warm with highs topping out in
the 65 to 70 degree range.  Lows Saturday night look to drop back in
the lower 50s.

.Long Term...(Sunday through Friday)
Issued at 327 PM EST Fri Jan 20 2017

Sunday through Monday Night...

...Storm System To Pass South of the Region Sunday and Monday...

A compact but stacked surface/upper level low will move from the far
southern Plains across the northern Gulf coast states late Sunday
and into the day on Monday.  Overall, the model solutions remain in
general agreement with the timing and track of the system.  The
SREF/NAM/GFS/CMC models have trended a little more north with the
system while the Euro has held its own tracking more or less to our
south.  The bulk of the convection with this system will move
through the heart of Dixie during the period.  However, decent lift
and dynamics will result in widespread showers and a few
thunderstorms moving through the region Sunday through Monday
afternoon.  The heaviest rainfall looks to fall mainly across far
southern Kentucky.  As the system pushes eastward, the rain showers
will diminish from west to east late Monday night.

Highs on Sunday will warm into the lower 60s with overnight lows in
the mid-upper 40s expected.  Highs Monday will be much cooler with
northerly winds driving some cooler air into the region.  Highs on
Monday look to top out in the upper 40s to near 50.  Lows Monday
night look to cool into the upper 30s to around 40.

Tuesday through Friday...

...Winter To Make Return To The Region By Late Week...

...Colder Than Normal Temperatures Expected for the Remainder of
January and into Early February...

In the wake of the upper level trough moving off the eastern US
coast, a short period of mid-level ridging will move into the region
for Tuesday and Tuesday night.  Mild temperatures are expected to
continue through the period.  Highs on Tuesday will be in the lower
50s with highs on Wednesday pushing back into the mid-upper 50s.
Overnight lows will be in the 40s.

The mild weather will give way to a colder pattern with the passage
of a frontal boundary during the day on Wednesday.  Much of the
moisture with this system will remain to our north, but enough lift
along the front may produce some isolated showers.  The more
sensible weather feature of note during Wednesday will be the gusty
winds as the pressure gradient tightens across the region.  Wind
gusts of 25-30 MPH and higher will be possible ahead and behind the
frontal boundary.  Cold air advection will be in full force
Wednesday night with temperatures falling through the evening hours
and bottoming out in the lower-mid 30s by Thursday morning.

By late week, we will see the well advertised upper level pattern
change in full swing.  The models continue to be in good agreement
with an eastern US trough developing with a corresponding western US
ridge.  This agrees well with the overall developing hemispheric
pattern with a +PNA and a neutral to slightly negative EPO
developing.  The overall pattern will feature below normal
temperatures for Ohio Valley for the remainder of the week and into
the first part of February.  With a deep/broad trough axis over the
eastern US, a series of disturbances are likely to drop out of
Canada and into the base of the trough.  These features will could
bring episodic bouts of wintry weather to the region starting next
weekend and into the last week of January.


.Aviation...(00Z TAF Issuance)
Issued at 605 PM EST Fri Jan 20 2017

Stratus ceiling has lifted to VFR at SDF and LEX, and even scattered
out at BWG. Lower ceilings to the north will be the main challenge
tonight, as guidance suggests that stratus deck will build southward
through the night. This TAF will reflect a low-confidence forecast
taking SDF and LEX down to MVFR toward daybreak, but ceilings remain
above fuel-alternate thresholds. Less cloud cover at BWG will be
more favorable for radiational cooling, and therefore more
restricted cig/vis. Just enough southerly wind to keep a little
mixing, and lift any potential fog into an IFR stratus deck.

By late morning stratus will scatter out to allow a VFR afternoon,
with SSW winds near 10 kt. Precip shield will spread in from the
south Sat evening, which only impacts the SDF planning period and
will be limited to VCSH for now.




Short Term...MJ
Long Term....MJ
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