Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 211122

Area Forecast Discussion
National Weather Service Louisville KY
622 AM EST Sat Jan 21 2017

...Updated Aviation Discussion...

.Short Term (Now through Sunday Night)...
Issued at 255 AM EST Sat Jan 21 2017

Broad southwest flow aloft and at the surface throughout today will
bring unseasonable to near record warmth across central Kentucky and
southern Indiana. As of early this morning, IR satellite showed
mid/high clouds streaming across the region thanks to convection
across southeast Texas and southwest Louisiana. Most of the low
stratus has pushed north into central Indiana and Ohio, and locally
readings were very mild in the mid to upper 50s.

For today, a mid level perturbation will track across MS/AL/GA today
and this is where the focus for highest 850 mb moisture transport
exists as well. Clusters of convection will likely stay well south
of our area and prevent any northward transport of higher moisture.
As a result, believe that most of the area will stay largely dry for
today, and have cut down precipitation chances across the board.
This agrees with the hi-res and near term models along with the
short term blended data sets.

The deep southwest flow and unseasonably mild start will allow
temperatures to rise well into the mid/upper 60s. Trended highs
above guidance and will forecast a few locations to reach or
slightly exceed the 70 degree mark. This puts record highs in
jeopardy at our major climate sites: Louisville (72, 1906),
Lexington (72, 1906) and Bowling Green (71, 1999).

By late Saturday night and through the day Sunday, a more vigorous
closed mid level low will track across the southern Plains and into
central MS/AL. The higher focus for showers/storms will be confined
mainly south of the KY/TN border but should spread north into
central Kentucky Sunday. The 21.00z models continue to struggle with
the placement of precipitation bands as they pivot around the
stacked upper/surface lows. Some elevated instability remains in
place so will continue thunder mention through the period.  With
more clouds, cooler temperatures aloft and higher chances for
showers on Sunday, highs will stay mainly around the 60 degree mark.

.Long Term (Monday through Saturday)...
Issued at 258 AM EST Sat Jan 21 2017

By Sunday night and into early next week, the closed upper low is
forecast to track across the Carolinas and the mid-Atlantic. Cooler
air will filter across Monday southern Indiana and central Kentucky
as winds shift to the north/northwest. Widespread showers and
possibly some thunderstorms will be mainly confined to southern
Kentucky and portions of the Bluegrass.

Total rainfall for this system is expected to be from around a half
inch across southern indiana and north central Kentucky to near 1
inch across southern Kentucky.

Brief upper level ridging and surface high pressure on Tuesday will
give the area a dry day and seasonable temperatures. This is
replaced quickly by a stronger low pressure system forecast to track
from the central Plains toward the Upper Midwest, bottoming out
around 990 mb over Iowa. A cold front is forecast to pass the area
sometime on Wednesday but a real lack of moisture will make it more
a wind shift and mark the leading edge of a colder pattern change.

Ahead of that system though, a strong pressure gradient and deep
boundary layer mixing will make for very windy conditions. Soundings
show potential to mix down 30 to 35 mph wind gusts.

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. With the deep cyclonic flow, we`ll have to watch for
disturbances and perturbations to work into the flow. The GFS
advertises deeper moisture and potential for rain/snow showers while
the ECMWF is much drier, but just as cold.

For now, will advertise below normal temperatures and slight chances
for rain/snow showers confined mainly to southeast Indiana and the
northern Bluegrass regions.


.Aviation...(12Z TAF Issuance)
Issued at 615 AM EST Sat Jan 21 2017

VFR conditions are expected throughout the day today with breezy SSE
winds.  The next weather system will arrive tonight as a strong
upper low moves through the OH/TN valleys bringing several bands of
showers and isld t-storms.  At this time, t-storm chances are too
slim to mention in the TAFs.  However will go ahead and start VCSH
after 0Z tonight with the first rain band and MVFR conditions
getting into BWG around 6Z...SDF around 9Z...and LEX around 10Z
respectively. Some models also indicate IFR cigs toward sunrise
tomorrow so will trend in that direction.




Short Term........ZT
Long Term.........ZT
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