Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 161432
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1032 AM EDT Sun Mar 16 2014
Issued at 1030 AM EDT Sun Mar 16 2014
Rain working in from the southwest has overspread our southern
forecast area, yet is trying to overcome dry air across the northern
third of the CWA. As this occurs, surface temperatures are trending
down as we wetbulb. Dewpoints across our northern half are generally
in the low to middle 20s. Gusty northeast winds continue to try to
advect colder air in here. Temperatures are at or below freezing
just to our northeast. So, with some advection combined with
wetbulbing, temperatures should continue to cool through the morning
and afternoon hours. Latest aircraft soundings indicate a very warm
layer of about +7C at about 870 hPa. Have not come across a sounding
with a dewpoint curve though. Models generally have this warm nose
and cool it rather quickly (wetbulbing) as they indicate quite a bit
of dry air at that level.
Afternoon still looks good for a changeover from rain to a mix,
though may have to fine tune that as the day progresses. The 12Z NAM
has arrived and has shifted the main precip band a little farther
north, which lines up more with 06Z GFS. These place the
accumulations along the Ohio River and eastward into the northern
Bluegrass region. Still think snow and sleet amounts these spit out
are a bit high in places. Watching the RAP this morning shows it
ever so slightly fluctuating by about the width of a county or two
between a southern and northern snow/sleet band. However, this band
is farther south than the NAM and GFS, placing the best
accumulations south of the Ohio River. The SREF probabilities have
seemed to be the most consistent and is what was leaned toward
yesterday. With the 09Z SREF data having just rolled in, it still
depicts the best accumulation potential from Perry County in Indiana
east-northeastward to Harrison/Nicholas Counties in Kentucky. The
SREF seems to capture the slightly more northern GFS/NAM and
Given this data, see no reason to make any changes to the running
forecast at this point, just a few minor updates in the very near
term. The Advisory will stand as is for now. Believe our northern
most counties in Indiana (Washington, Scott, Jefferson) still have a
chance to pick up around an inch across their south. Our far
southeast, Casey and Lincoln Counties in Kentucky still have a
chance to pick up around an inch in their north.
.SHORT TERM (Now through Monday)...
Issued at 317 AM EDT Sun Mar 16 2014
...Accumulating Snow Expected This Afternoon and Tonight...
After a beautiful warm day on Saturday, today will bring quite a big
change as wintry weather returns for (hopefully) one last hurrah. A
surface low over Arkansas this morning will track east across the
northern portions of the Gulf Coast states today and this evening. A
large precipitation shield associated with this low will spread into
south central KY by around daybreak or just before and then spread
northward through the morning hours.
Precipitation type is still a challenge with this system. The
forecast hinges on how much cold air will be drawn into the area
today on the northern side of the low pressure system. Central
Indiana this morning has fallen into the mid to upper 30s, so there
is cold air to the north of the forecast area. Additionally, there
is a warm layer aloft that will slowly cool through the day. As
mentioned in previous discussions, this warm layer is not as robust
as in previous systems and therefore will likely not result in
complete melting aloft. This may lead to some sleet as precipitation
transitions from rain to snow from north to south today.
The other challenge with this system is the models are still in some
disagreement as to where a heavier band of precipitation will set
up. The GFS is the farthest north with this band and has it along
the Ohio River while the NAM has it between the Parkways and the
Euro has it across south central KY. Some of the higher resolution
models paint the band just south of the Ohio River into the
Bluegrass region, and this seems a reasonable consensus.
Taking everything into consideration, the forecast remains fairly
close to the previous forecast. It looks like there will be a mix of
rain/snow/sleet across southern Indiana and far north central KY
this morning if the precipitation moves in there that fast. The
transition line will sink southward through the afternoon hours and
into this evening as the colder air filters in. Drier air will
filter in fairly quickly on the back side of the system tonight,
though some lingering freezing drizzle around the Lake Cumberland
area may be possible late tonight. Dry conditions are expected
Snow totals are tricky given the possibility of sleet and the fact
that initially there will likely be some melting with the antecedent
warm ground. Accumulations will be most likely on grassy and
elevated surfaces, but if there are some heavier bursts of snow
roads may become slick at times. Lowered snow totals just a bit.
Most areas in the Advisory look to receive around an inch with 1-2
inches in the Bluegrass region. Some locally higher amounts are
certainly not out of the question, however. Falling temperatures
tonight also may lead to some slick spots on roadways for the
morning commute Monday.
In addition to the precipitation, winds will become gusty today as
the pressure gradient tightens up across the area. Sustained winds
of 15-25 mph with gusts up to 35 mph can be expected.
.LONG TERM (Monday Night through Saturday)...
Issued at 250 AM EDT Sun Mar 16 2014
A fairly nice work week is in store with overall temps slightly
above normal for a change. The northern stream will remain active
this coming week pushing weak cold fronts through our region Wed and
Fri Night/Sat. Ridging will control the region Tues drawing warm
air northward and allowing temps to rise into the upper 50s and
lower 60s for highs. Tues night the frontal boundary will approach
the area bringing a chance for rain showers late Tues night or Wed.
Long range models vary on timing slightly so will stick with current
forecast for consistency which matches the last few runs of the
ECMWF best. The next front looks to come through sometime Fri night
or Sat. Still a good range in timing/strength amongst models with
this front as well. At this point, neither fronts this week look
too strong or look to contain a great amount of moisture. Think
that light rain showers will likely accompany both fronts. A t-storm
or two may also be possible. Winds may become gusty on either side
of the fronts especially Wed and Sat. Wind gusts in the 20-30 mph
look likely on these days.
As for temps, the area will be in the upper 50s/lower 60s for highs
most of the week. Friday will be a bit warmer, though, in the mid
to upper 60s (maybe even some low 70s) for highs as a strong
southerly wind brings in warmer temps. Low temps will range
throughout the 30s and 40s this week.
.AVIATION (12Z TAF Update)...
Updated at 645 AM EDT Sun Mar 16 2014
Winds have already started to become gusty this morning as a low
pressure system passes the area to the south. Winds through the day
will be out of the northeast and sustained from 10-20 knots with
gusts to around 25-30 knots. Winds will relax a bit tonight, but
still remain gusty.
Rain will overspread the area this morning. Ceilings are expected to
lower to MVFR with this rain. BWG may see IFR ceilings for awhile as
well. Rain will change over to snow at LEX and SDF this evening as
colder air filters in. Precipitation will move out late this evening
into the overnight hours. This should bring some improvement to
ceilings and visibilities.
KY...WINTER WEATHER ADVISORY from 2 PM EDT /1 PM CDT/ this afternoon
to 8 AM EDT /7 AM CDT/ Monday FOR KYZ023>025-028>043-
IN...WINTER WEATHER ADVISORY from 2 PM EDT /1 PM CDT/ this afternoon
to 8 AM EDT /7 AM CDT/ Monday FOR INZ076>079-083-084-