Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 130839
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
339 AM EST Fri Dec 13 2013
.SHORT TERM (Now through Saturday Night)...
Issued at 335 AM EST Fri Dec 13 2013
...ANOTHER ROUND OF SNOW LIKELY TONIGHT FOR SOUTHERN INDIANA AND
PORTIONS OF NORTHERN KENTUCKY...
No changes to the current Winter Wx Advy are planned for this
forecast package although did debate throwing in Oldham and Henry
Counties in KY. The most challenging parts of this forecast which
will affect p-type and snow amounts are the initial thick layer of
dry air in the low levels initially and what the new temp profile
will look like once things saturate. For locations over southern
Indiana, the resultant sounding will most likely be a snow sounding
and so we have the Winter Wx Advy in effect. Suspect that where
there is snow pack right now, temp profiles will tend to stay on the
colder, snowier side with the antecedent colder air in place due to
the snowpack. For this reason, Oldham and Henry counties which
still have a decent snowpack were considered for this advy and may
very well be added later today in coordination with surrounding NWS
offices. Generally speaking though, locations south of the Ohio
River will have more of a questionable sounding closer to the
freezing mark and it`s hard to determine where that rain/snow line
may form, thus will continue the SPS for north and east central KY.
To start the day today, skies will be mostly clear with temps in the
upper teens to around 20. A warm southerly flow will allow temps to
warm into the mid 30s to mid 40s for highs this afternoon with
Think that the arrival of precip will hold off until after sunrise
although we may start to see some radar reflectivity echos
indicating virga just to our west by late afternoon or early
evening. The atmosphere should saturate enough to produce at least
light precip some time between 0-4Z. That precip will likely be in
the form of a rain/snow or snow grain mix until the air column cools
yielding snow over southern Indiana and rain over south central KY
with a mix some where over north and east central KY. Tonight
expect southern Indiana to see 1-3 inches of snow with locations
along and south of the river likely to see up to an inch of slushy
By Sat mid to late morning, we`ll see a surge of warm air as the sfc
low makes its way through central/east central KY. This will cause
a change over to all rain over most areas except maybe a line from
Jasper to Madison, Indiana which may stay all snow or have a mix of
rain/snow. Either way, temps should rise above freezing for most if
not all locations causing any morning snow accums to melt Sat. Highs
are expected to be in the mid 30s to mid 40s Sat afternoon.
As the low pressure system moves off to the northeast, cold air will
rush back into the region Sat night causing left over shallow
moisture to precipitate out as either freezing drizzle or light
snow. This light moisture on the back side will have the potential
to produce slick spots for late Sat night/Sun morning. Sun morning
lows will be in the 20s to around 30.
.LONG TERM (Sunday through Thursday)...
Issued at 305 AM EST Fri Dec 13 2013
After an active first half of the weekend, most of the long term
will be rather quiet. Northwesterly flow will remain in place aloft
through Wednesday. It will then transition through Friday as a
trough moves into the plains and ridging builds over the Atlantic. A
couple of waves will move through the northwesterly flow aloft. Most
of the precipitation associated with these waves should stay north
of the forecast area. There may be a slight chance to see some
precip Monday evening across southern Indiana and north central
Kentucky. However, am not confident enough at this point to put any
mention of this in the grids. The next significant system will be at
the end of the week as a strong cold front approaches the area. This
system is just beyond the end of the forecast period at this point.
Temperatures will slowly warm through the week, though they may be
affected by the shortwaves moving across the area. This will depend
on how far south these waves dive. Temperatures will be coldest
Sunday with highs only in the upper 20s to lower 30s. By mid week
temps will rise to the upper 30s to mid 40s with temps close to 50
across south central KY by Thursday. Lows in the teens to lower 20s
early in the week will shift to lower 40s by the end of the week.
.AVIATION (06Z TAF Update)...
Updated at 1220 AM EST Fri Dec 13 2013
Sfc high pressure will remain in the control of the region through
this evening providing VFR conditions. Upper level clouds will be
on the increase ahead of a low pressure system approaching from the
southwest. The cloud deck will begin to steadily drop this evening
as moisture associated with the low pressure system enters the
area. A thick dry layer in low levels will exist ahead of this low
pressure system so expect some precip to begin to reach the ground
in the form of very light rain or snow Fri evening, but the bulk of
precip will likely arrive after midnight when better saturation is
reached (just beyond this TAF period for BWG/LEX). According to
model soundings, late night precip would likely be in the form of
light rain or snow at SDF. When low levels finally do saturate, at
least low end MVFR conditions can be expected.
Winds will remain out of the SSW through this evening. Winds will
become predominantly SE as the low pressure approaches tonight.
KY...WINTER WEATHER ADVISORY from 7 PM this evening to 10 AM EST
Saturday FOR KYZ032.
IN...WINTER WEATHER ADVISORY from 7 PM EST /6 PM CST/ this evening to
10 AM EST /9 AM CST/ Saturday FOR INZ076>079-083-084-