Area Forecast Discussion
Issued by NWS Louisville, KY
FXUS63 KLMK 291711
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1211 PM EST Fri Nov 29 2013
...Updated Aviation Discussion...
.SHORT TERM (Now through Saturday)...
Issued at 320 AM EST Fri Nov 29 2013
IR satellite and surface observations reveal clear skies across the
forecast area this morning. Temperatures were generally in the
lower to middle 20s with some of the normally cooler/rural spots in
the middle to upper teens. Expect temperatures to continue cool
another degree or two before sunrise.
High pressure cell over the eastern Appalachians will drift off to
the east today and be replaced by another high pressure cell moving
from the Midwest into southern New England. These features will
continue provide the area with dry weather and mainly clear skies.
Under sunny skies today, we should see temperatures warm into the
lower 40s across southern Indiana and the northern half of
Kentucky. Middle to upper 40s will be possible across southern KY.
A mostly clear night is expected tonight but overnight minimum
temperatures should be a little more mild that what we see this
morning. Consensus raw model guidance shows lows in the lower to
middle 20s across the region. Mostly sunny skies are expected again
on Saturday with highs warming into the upper 40s across southern
Indiana and northern Kentucky with lower 50s likely across the
southern half of Kentucky.
.LONG TERM (Saturday Night through Thursday)...
Issued at 313 AM EST Fri Nov 29 2013
The start of the long term period will feature split upper-level
flow, with confluence of this flow across the Ohio Valley. Several
quick-hitting shortwave troughs will affect the Commonwealth within
this split-flow regime before a strong trough builds into the
western CONUS by the middle of next week. Downstream ridging will
build over the Ohio Valley in response to this trough, leading to
warmer yet increasingly unsettled conditions by the end of the long
The first shortwave trough sliding through the flow aloft will
affect the region Saturday night into Sunday. Forecast
cross-sections shows this initial wave as being quite
moisture-starved, likely only bringing some increasing cloudiness.
High temperatures on Sunday will top out in the upper 40s and lower
50s, as southerly flow commences on the back side of a departing
Another disturbance will dive across the region Sunday night into
Monday. This system continues to remain a challenge as far as
forecasting pops go, as it looks to be a cloudy, drizzly scenario
where a hundredth or two of measurable precip could be possible in a
few isolated locations. The best forcing has trended quicker in the
latest guidance, which may bring this drizzle/isolated shower into
the region by Sunday night. To avoid flip-flopping the forecast,
will leave measurable precip out of Sunday night forecast for now,
but this may need to be added if quicker trends continue. With the
expected cloud cover on Monday, highs Monday will likely be a few
degrees cooler than Sunday.
Guidance then begins to diverge quite a bit by Tuesday through the
remainder of the long term period. The 29/00Z GEM/ECMWF try to
linger precip across the area Monday night into Tuesday. However,
forecast soundings show rather unimpressive moisture profiles, thus
will lean toward the drier and slightly more consistent 29/00Z GFS.
Forecast confidence continues to decrease by Wednesday, as guidance
remains split on the degree of ridging we`ll experience out ahead of
the western trough. The ECMWF had been less amplified with the
ridge, thus quicker with the precip, while the GFS has been more
amplified and slower. Over the past 24 hours, the roles have
reversed, with the 29/00z ECWMF now slower and more amplified. With
such inconsistency, will continue to lean on a blend of the
NAEFS/GEFS ensemble means. However, given the strength/amplitude of
the digging trough in the west, think the more amplified (slower)
pattern will likely win out in the end.
.AVIATION (18Z TAF Update)...
Updated at 1210 PM EST Fri Nov 29 2013
High pressure over the region today will keep winds variable and
light. Just have a few high clouds streaming across the region so
far today. Saturday that high pressure will shift to the New England
area, so our winds will become more southerly during the day.