Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 241102
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
602 AM EST Sat Jan 24 2015
...Updated Aviation Discussion...
.SHORT TERM (Now through Sunday)...
Issued at 245 AM EST Sat Jan 24 2015
The synoptic pattern early this morning features a trough across the
eastern seaboard, with an upstream ridge situated just off the west
coast. This trough will actually be reinforced by another strong PV
anomaly diving southeast on Sunday, which will bring another round
of precipitation to the Ohio Valley.
The deformation band continues to slide east this morning, just
about out of the LMK CWA. Therefore, any additional accumulations
will only be a few tenths, and confined to extreme eastern LMK
counties in the northern Bluegrass and Lake Cumberland regions.
Will be expiring the Winter Weather Advisory and replacing it with a
Traveler`s Advisory for slick roads, as temperatures falling below
freezing coupled with partially snow covered/wet roadways will
likely lead to slick spots this morning.
Otherwise, southwesterly flow will commence today, helping to advect
in warmer temperatures. This coupled with expected sunshine should
efficiently melt the snow, although areas with 4+ inches will likely
remain cooler than surrounding regions. For this reason, have kept
those in the deeper snow confined to the upper 30s, with mid 40s
Clouds will increase tonight especially across the Northern
Bluegrass as a weak system slides through OH and WV. Otherwise,
additional cloud cover will push in/develop from the west out ahead
of the aforementioned PV anomaly by early Sunday morning. With the
expected clouds, overnight lows should hold in the low to mid 30s.
The 24/00Z guidance suite has trended a bit further south with the
strong PV anomaly and associated surface reflection for Sunday.
Dprog/dt shows this trend has gone on for several runs now, so it is
something we will need to watch. However, still appears any snow
chances on Sunday will stay off just to the north of the LMK CWA as
the boundary layer will warm too much to allow snow to reach the
ground. Therefore, expect showers within the warm advection regime
to develop by mid Sunday morning, especially across the northern
CWA. The associated surface cold front will spread additional
showers in from the west by late Sunday into Sunday evening as the
surface low swings by. Given the quicker/southern trend, cloud
cover looks to be more abundant on Sunday. Therefore, have lowered
highs into the lower 40s over southern IN, with upper 40s/low 50s
expected across southern KY where there will be a few peeks of
sunshine for the first part of the day.
.LONG TERM (Sunday night through Friday)...
Issued at 310 AM EST Sat Jan 24 2015
Low pressure will be centered near Louisville at the start of the
long term, and will move off to the east Sunday night. Precipitation
will be widespread Sunday evening but will gradually shift from west
to east out of much of the region overnight. Any lingering precip
on Monday morning would be in the far east and should end by mid
morning. Though precipitation will continue as rain early in the
evening, it will change over to snow from north to south as the
night progresses. Some light accumulations will be possible,
especially in southern Indiana and north central Kentucky. In
addition to the rain and snow, winds will be brisk from the
northwest, possibly gusting to around 20 mph. The combination of
wind, light snow, and temperatures falling into the middle and upper
20s should lead to slick roads Sunday night, possibly into Monday
morning. Something to keep an eye on over the weekend to see how the
Monday morning rush is shaping up.
On the heels of the departing weekend system, low pressure will dive
southeast from the upper Mississippi Valley to the Carolinas Monday
night/Tuesday, bringing us our next chance of precipitation. If we
do get some precip from this quick-hitting system, it would be in
the form of light snow Monday night and a light snow/rain mix
Tuesday. Again, some light accumulation will be possible,
especially late Monday night.
It should be noted that these two weather-makers are completely
different types of systems than what came through Friday evening.
The Friday snow was from a large southern stream storm with good
access to available moisture. The Sunday night-Tuesday systems will
be more compact and coming in from the northwest with less moisture
available. Still something to keep an eye on, though, as even light
amounts of snow can cause problems.
Models are in pretty good agreement late in the week as they bring
low pressure across the Plains and phase it with upper level energy
and moisture coming in from Canada. Widespread precipitation is
expected to break out from the Ohio Valley northward Thursday and
Thursday night. Precip on Thursday would be rain, but would then
transition to light snow Thursday night.
Overall, temperatures in the long term really won`t be too bad for
January. The warmest afternoon will come on Thursday as the mercury
reaches the upper 40s and lower 50s. Wednesday morning will be the
coldest time, with readings in the lower 20s.
.AVIATION (12Z TAF Update)...
Issued at 600 AM EST Sat Jan 24 2015
Conditions continue to improve this morning, as any lingering snow
has moved out and ceilings rise. IFR cigs continue at KLEX.
Considering generally weak low-level flow, think it may be a couple
more hours before these IFR cigs scour out, so will continue them
just a bit longer. Otherwise, after some light morning BR/HZ at
KBWG, conditions should improve to VFR at all sites by later this
morning. Winds will increase out of the WSW, with some gusts around
15 knots possible at times.
For tonight, mid/upper level clouds will begin to stream in from the
northwest. Additionally, low-level moisture will be on the increase
ahead of a system approaching for Sunday. If some snow is able to
survive today`s melt, then some fog/low stratus will be increasingly
likely tonight. Will hint at this potential with a SCT010 deck for