Area Forecast Discussion
Issued by NWS Louisville, KY

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FXUS63 KLMK 221903

Area Forecast Discussion
National Weather Service Louisville KY
303 PM EDT Thu Mar 22 2018

.Short Term...(This evening through Friday night)
Issued at 220 PM EDT Thu Mar 22 2018

Afternoon surface analysis showed high pressure across Illinois
through western Kentucky and the lower Mississippi River Valley.
Clear skies prevailed and readings varied from around 50 degrees
across southern Kentucky to upper 30s and lower 40s in the remaining
snow pack across north central Kentucky and southern Indiana.

Expect a mostly clear night with the high pressure slowly moving to
the east. Mid-level moisture associated with lift overrunning a warm
front across Missouri will bring increasing clouds from the west
this evening, becoming mostly cloudy to overcast after midnight west
of I-65. This should keep readings from bottoming out too much with
low 30s expected. Across the east into the Bluegrass, clearer skies
and lighter winds will allow readings to drop into the mid/upper

There remains some threat of isolated black ice overnight with more
melting taking place. Motorists should be aware of the possibility
heading into the Friday morning commute.

Friday is expected to be dry for most areas, except for a weak
weather system may bring showers to west central Kentucky by
afternoon. Plan on partly to mostly cloudy skies everywhere and
highs reaching around 50 degrees.


.Long Term...(Saturday through Thursday)
Issued at 302 PM EDT Thu Mar 22 2018

...Wintry Mix Possible Saturday Across Northern Bluegrass...

Main forecast challenges in the long term are precipitation type,
amounts, and impacts Saturday followed by active and unsettled
weather next week.

As the warm front begins to move closer to central Kentucky and
southern Indiana, and isentropic lift increases Friday night,
overrunning precipitation should break out in a northwest to
southeast oriented band over the forecast area. This will increase
in coverage after midnight. At the surface, stronger easterly flow
is expected and this will hold in a shallow cold dome of air that
could result in a wintry mix across the far northeastern forecast
area, generally north/east of Louisville and Lexington toward

22.12z models trended colder and further southwest with the
precipitation axis compared to previous runs. Soundings for
locations around Madison, IN and north of Lexington, KY to have
around freezing surface temperatures with near 0C thermal profiles
aloft. Then, southwest flow in the mid levels will advect a strong
warm nose at 850 mb, perhaps resulting in some sleet to freezing
rain changeover. As surface temperatures then warm above freezing
Saturday late morning or afternoon, ptype would become all rain. The
current forecast calls for snow to wintry mix to rain across the far
northeastern areas with some accumulations of snow/sleet and ice
accumulation. Confidence is low with this system, and slight
deviations in surface temperatures by 1-2 degrees, and the track of
the surface low, will have big changes in the types and potential
amounts. Those living north of I-64 in Kentucky and across southeast
Indiana should monitor the forecast very closely over the next 48-60
hours for the changes in the forecast, potential of accumulating
snow, and impacts to travel.

Otherwise, a cold rain, heavy at times, will spread across the rest
of southern Indiana and north central Kentucky. Several pockets of
rain will pass through, so will continue to carry near 100 percent
chances. Total amounts of 1 to 2 inches are expected. Locally higher
amounts near 3 inches possible across southern Indiana and north
central Kentucky. This could create localized hydro issues,
especially for small streams, creeks and urban areas.

The surface low tracks through middle TN or southern KY Saturday and
will bring a sharp, large temperature gradient to the area. With 30s
in the north, low 60s are likely across southern Kentucky in the
warm sector. Precipitation will begin to wrap around then end west
to east Saturday night. We`ll begin drying out Sunday as upper level
ridging builds in.

Southwest flow aloft is expected next week with ridging through the
Ohio Valley early in the week. With this ridging, moderating
temperatures into the 60s are likely but also with periodic chances
of showers and thunderstorms. Of course, the big concern with this
setup would be flooding, but there is still some uncertainty as to
where the heaviest axis of rainfall will end up. Plan to keep higher
PoPs in the forecast for the long term, and will continue to monitor
the setup for any potential flooding.


.Aviation...(18Z TAF Issuance)
Issued at 1245 PM EDT Thu Mar 22 2018

Clear skies and light NW winds are expected this afternoon. Cirrus
will start to spread in later in the evening as a warm advection
pattern aloft sets up, but sfc winds go light/variable if not calm.
Gradual lowering and thickening of clouds ahead of the next system,
so will bring in a mid-level ceiling by daybreak, and keeping it VFR
as it lowers, including in the afternoon at SDF. Could see enough
precip Fri morning to warrant a VCSH at BWG and HNB but even that
seems generous as we hold it off beyond the valid TAF period at SDF.




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