Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 220832
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
332 AM EST Mon Dec 22 2014
.SHORT TERM (Now through Tuesday)...
Issued at 320 AM EST Mon Dec 22 2014
IR satellite imagery and surface observations reveal partly to
mostly cloudy skies across the region. Low-level cloudiness was
most prevalent across southern/southwestern KY. This has kept
temperatures up in the upper 30s to the lower 40s. Further north,
where partly cloudy skies were noted, temperatures were in the upper
30s to the lower 30s. We expect cloud cover to increase across the
region as the overnight hours wear on.
For today & tonight, an increasing southerly flow will help
transport more moisture into the region. Increasing isentropic lift
and warm air advection should lead to more widespread cloud cover
with some sprinkles or drizzle possibly developing during the late
afternoon hours. Afternoon temperatures should warm into the upper
40s to the lower 50s in the north with mainly lower-mid 50s across
More widespread precipitation is expected to develop this evening
and into the overnight hours as an upper level wave punches through
the region. With a southwesterly flow remaining in place,
temperatures will not drop off that much with readings dropping into
the lower-mid 40s in the north and mid-upper 40s in the south.
For Tuesday, we`ll continue to see continued cloudiness. We`ll
remain in the southwesterly flow with several mid-level waves
passing through the region. We`re likely to see a bit of a dry
punch move in from the west (as suggested by the NAM/GFS solutions).
The atmosphere will continue to moisten with the southerly flow, but
cloudy conditions look to keep instability rather low. Can not rule
out some isolated rumbles of thunder out across the region on
Tuesday as well...where enhanced pockets of sfc based instability
could develop. It will remain a mild day with temperatures warming
back into the mid-upper 50s.
.LONG TERM (Tuesday Night through Sunday)...
Issued at 311 AM EST Mon Dec 22 2014
The forecast for the first half of the long term remains a bit
complicated due to model trends and spread along with the potential
for snow on Christmas Eve. For Tuesday night a low pressure system
will move northeast from the Gulf Coast. This low will cross the
forecast area during the day on Wednesday and into the Great Lakes
region by Thursday morning.
The models are still having some difficulty agreeing on the track of
this low, which will have big impacts on the temperatures and thus
sensible weather for Wednesday and Wednesday night. There has been a
slight trend in the models to the east with the track. The GFS/ECMWF
would bring the low directly across the forecast area. The SREF is
slightly further to the northwest while the NAM is an outlier to the
east. For now will lean heaviest on the GFS/ECMWF combined with the
Given all this, we will start out with a good chance for rain
Tuesday night and Wednesday. Temperatures will be falling Wednesday
and Wednesday night as the low pulls northeast. Highs on Wednesday
will be in the morning for most of the area and there will be a
sharp temperature gradient. As temperatures fall and the column
cools a changeover to snow is expected sometime in the evening
Christmas Eve. If solutions continue to trend easterly, this
changeover will occur earlier. At this time QPF looks to be light
after the changeover to snow. As mentioned in previous discussions,
it is expected to be gusty Wednesday night and some convective snow
showers are not out of the question along with some minor snow
accumulations. However, the ground will be wet and surface
temperatures will be marginal, so significant accumulations seem
Precipitation should move out by Thursday morning, though a few snow
showers may linger in the east. Temperatures will rise into the
upper 30s to lower 40s. The next front will move through Friday into
Saturday. This system looks to have less moisture associated with it
so precipitation should be fairly light. Depending on timing of the
precip, we could see a light wintry mix Friday night. Dry conditions
are then expected to cap off the weekend with high pressure building
across the region.
.AVIATION (06Z TAF Update)...
Issued at 1155 PM EST Sun Dec 21 2014
Low level moisture will be on the increase overnight as a southerly
wind flow kicks up across the region. Extensive area of low clouds
will continue to advect northward overnight bringing broken to
overcast ceilings to the TAF sites. Ceilings look to start off as
VFR but should fall to MVFR levels around 22/10-11Z.
Southerly flow will deepen throughout the day in advance of a
surface low pressure system moving into the Mid-Mississippi Valley.
Expect isentropic lift to result in a lowering of ceilings during
the late afternoon with showers developing from west to east. More
widespread precipitation will be commonplace after 23/00Z with MVFR
visibilities and IFR ceilings developing.