Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 261119
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
619 AM EST Wed Nov 26 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Thursday)...
Issued at 330 AM EST Wed Nov 26 2014
...Wintry Mix Tonight and Early Thursday Morning...
In the near term, quiet weather was noted across the forecast area
this morning. On IR satellite this morning, a classic baroclinic
leaf structure was observed over our area. This feature has led to
mostly cloudy skies over the eastern half of the state while the
western sections of the state have remained mostly clear. Within
the cloudy areas, temperatures were generally in the mid-upper 30s.
However, in the clear areas, temperatures had fallen off into
lower-middle 20s. Over the next few hours, we expect the cloudiness
in the east to lift eastward. This should allow temperatures out in
the central sections to fall into the upper 20s to the lower 30s.
For today, we`ll start off dry across the region as high pressure
pushes eastward and away from the region. Clouds will be on the
increase throughout the day as a fast moving clipper system will
approach from the northwest/west. Highs this afternoon will likely
warm into the lower 40s in the north with mid-upper 40s across the
south. As the clipper approaches, strong mid-level frontogenesis
will increase within the tight gradient of the jet streak
approaching aloft. This will allow precipitation to streak in from
the west late this afternoon. At this time, it appears that the
best chances of rain this afternoon will be out across our
southwestern half of the forecast area, with lesser chance up across
the Bluegrass region.
For tonight, the latest guidance continue to be in general agreement
with swinging the clipper through the region. There continues to be
some variability in the track of the system. The NAM guidance is
still on the southern side of the envelope while the GFS solutions
are a little more north. Tracks aside, the challenge here will be
where and/if a narrow band of heavier precipitation develops just
north of the eventual surface track. Low-level thermal profiles
continue to start off warm with precipitation starting off as mainly
rain. However, as heavier precipitation develops this may result in
some colder air being dragged down and pushing the profile cold
enough to produce snow...despite surface temps above 32. Wetbulb
temps still look to be just above freezing through much of the event
At this time, we believe that we`ll see a band of moderate
precipitation move across our southern half of the forecast area
this evening. As mentioned above, a very narrow band of moderate to
even heavy precipitation may develop. As the evening wears on, we
should see all precipitation change over to snow by midnight and
then taper off from west to east during the late night hours.
Surface temperatures are likely to remain in the lower-middle 30s
(and above freezing) for much of the event. So despite it snowing,
the relatively warm ground and expected surface temperatures will
likely limit overall accumulations...to mainly elevated and grassy
surfaces. The best chances of snow accumulations would be along and
south of I-64...mainly in a swath from Owensboro to Somerset. For
now, plan on going with an inch or less of accumulation. However,
upcoming shifts will need to monitor upstream data and later runs to
see if additional changes to the forecast will be required.
For Thursday, some lingering snow flurries will be possible in the
morning before skies start to clear in the afternoon from west to
east. It will be a cold Thanksgiving with highs only warming into
the mid-upper 30s across the region.
.LONG TERM (Thursday night through Tuesday)...
Issued at 247 AM EST Wed Nov 26 2014
The long term will begin Thursday night with high pressure building
in from the west. Temperatures will be chilly with lows in the lower
to mid 20s. The high pressure will shift east of the area Friday
bringing a return to southerly winds.
Southerly flow will continue into the weekend as the high pressure
remains just off the eastern seaboard. Meanwhile, a low pressure
system will move out of the upper Midwest and across the Great Lakes
region. The cold front associated with this looks to slowly move
through Sunday night into Monday. With warm and moist air flowing
into the region ahead of this front, scattered showers will be
possible Saturday night and Sunday. The best chance for rain will
be Sunday night and Monday as the front moves through. A few showers
may hang around Monday night as the front continues to slowly sink
southward. However, Tuesday itself looks to be dry with high
pressure ridging in from the north.
Temperatures will warm quite nicely this weekend. While highs on
Friday will be in the 40s, by Sunday they look to top out in the
lower 60s. Lows Sunday morning will fall only into the upper 40s to
lower 50s. Temperatures Monday will be tricky with the cold front
moving through and cooler air filtering in behind it. At least a
part of the area should see some warming through the day, however.
.AVIATION (12Z TAF Update)...
Updated at 619 AM EST Wed Nov 26 2014
VFR conditions are expected through much of the day at the terminals
as we sit between weather systems. The next weather system in the
form of an Alberta clipper will drop southeastward into the region
late this afternoon and this evening. As this system approaches it
will bring clouds and precipitation in the form of rain. Based on
the latest data, the best precipitation chances look to be at KBWG
through the period...with just more scattered rain showers at KLEX
and KSDF. As the column cools tonight, the rain is expected to mix
with and change over to snow before diminishing by early Thursday
morning. Primarily VFR conditions are expected at KSDF and KLEX,
however, it appears that a period of MVFR conditions will be likely
at KBWG mainly between 27/04-10Z. Conditions look to improve by
27/10-12Z at all the terminals as the clipper system pulls on off to