Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 121036
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
636 AM EDT Wed Mar 12 2014
...Updated Aviation Discussion...
.SHORT TERM (Now through Thursday)...
Issued at 245 AM EDT Wed Mar 12 2014
Baroclinic leaf structure on water vapor loop indicates the
deepening process is beginning for the surface low, now along the
southern IL/IN border. The low has been a little slower to deepen
than originally forecast, but that difference will make little
impact in the rest of today`s forecast. Rapidly moistening airmass
in the warm sector should allow for showers and storms to form
through the morning hours, ahead of the surface cold front.
Models have been advertising quite a wallop of gradient winds behind
the cold front, and that is still on tap, with gusts of 35-45 mph
likely today. Thus the wind advisory looks good. There may be a
brief break in the precip behind the cold front this morning, but
cloud cover associated with the cold conveyor belt will get here
this afternoon, providing a brief window of opportunity for
additional showers. At that point, temperatures will start being
close enough to mention rain or snow showers, and should that
continue later in the afternoon and early evening, especially over
the northeast, we could see a brief period of just snow showers.
Given the recent warmup, ground temperatures should be too warm for
any significant accumulations. Still will have to watch
webcams/reports for quick reductions in visibility.
Temperatures will continue dropping quickly with the continued
moderate northwest winds tonight, with lows ranging from the mid
teens to mid 20s. High pressure will move into the area Thursday,
allowing for lighter winds and mostly sunny skies. Still highs will
be some 10-15 degrees below normal.
.LONG TERM (Thursday night through Tuesday)...
Issued at 300 AM EDT Wed Mar 12 2014
A split jet flow will move east of the Mississippi late Thursday in
the wake of a deep cyclone moving northeast of Maine. Two 500mb
troughs will be embedded within these two jets at this time, a
shortwave northwest of Lake Superior and a positively tilted trough
associated with the southern stream near Las Vegas. This northern
shortwave will eventually bring a weak cold front southeast of the
Ohio during the day Saturday.
By late Thursday, southerly flow will develop at the surface as
surface ridging moves to the east. Low temperatures will moderate
quite a bit early Friday compared with lows Thursday. Expect lows in
the lower to mid 30s. Much warmer temperatures will arrive Friday
afternoon thanks to brisk southwesterly winds that may gust from 20
to 30 mph during the afternoon. Highs will range from near 60 to the
mid 60s. Clear to partly cloudy skies are anticipated from late
Thursday through early Saturday. A weak cold front will move into
the Commonwealth Saturday, but winds will stay quite light and any
cooling will be minor. Cloud cover will increase, but a lack of any
appreciable moisture will limit precipitation chances Saturday to
just a slight chance. Expect Saturday`s highs to remain in the 50s.
By early Sunday, the southern branch of the jet will assume a
positively tilted trough, with the base forecast to lie over New
Mexico. The northern branch is expected to feature troughing across
the Great Lakes. Recent guidance has diverged in the handling of
this southern stream shortwave, and whether it will interact with
the northern stream trough. The GFS brings strong surface high
pressure southwards into Kentucky late Sunday, and suppresses any
southern stream feature well south. The Canadian, on the other hand,
moves low pressure far enough north, across northern Alabama, that
some light precipitation will make it as far north as the Ohio
during the day on Sunday. The newest ECMWF also hints at a cold rain
Sunday across the Commonwealth.
Northerly winds Sunday will bring cooler temperatures through
Monday. The amount of cooling will depend on how robust the Great
lakes high becomes and how far south the real arctic chill over the
Great Lakes drops. Highs Sunday and Monday may stay in the 40s.
Under partly cloudy skies, temperatures will moderate into the 50s
.AVIATION (12Z TAF Update)...
Updated at 635 AM EDT Wed Mar 12 2014
Cold front approaching the SDF/BWG terminals, and should be through
each by 12Z. Will allow for more variable winds that first hour,
given a line of showers and occasional thunderstorms right along the
frontal boundary. A more solid west northwest wind will follow that
line with gusts of 30-40 knots into the afternoon. Low clouds will
persist. May get a brief break in precip before another lighter rain
and possibly snow comes back for the afternoon. Conditions should
improve quickly this evening, with winds weakening and skies
KY...WIND ADVISORY until 8 PM EDT /7 PM CDT/ this evening FOR
IN...WIND ADVISORY until 8 PM EDT /7 PM CDT/ this evening FOR