LMK issues Area Forecast Discussion (AFD) at Dec 15, 6:53 AM EST ...Updated Aviation Discussion...642
FXUS63 KLMK 151153
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
653 AM EST Sun Dec 15 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Widespread rain transitions to drizzle before ending this
afternoon.
* Additional waves of rain are expected Tonight/Monday and Tuesday
Night/Wednesday with isolated thunder chances. Possible ponding
and nuisance flooding.
* Cold temperatures return late next week. Still low confidence in
flurries or light snow by the end of next week.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 327 AM EST Sun Dec 15 2024
This morning, the stacked low that is bringing all the rain is
currently located over northern Illinois. This is placing a lot of
wind energy at all levels over the Lower Ohio Valley. A 55-65 knot
low level jet and strong isentropic lift are driving the rain
showers that are streaming to the northeast over southern Indiana
and central Kentucky, but as we head through the morning, the low
pressure system will begin to weaken and dissipate as the surface
low fades, and the upper low gets carried off to the northeast by
upper flow. Isentropic lift will drop off, but some will remain from
around Nashville, TN and off to the northeast through the Lake
Cumberland region. Most of the heavier rain will come to an end
fairly early across our western counties before working eastward,
but even as the "rain" comes to an end, model soundings show lots of
low level moisture sticking around below the DGZ, around 800mb. The
rain will likely be replaced with drizzle to around midday. During
the afternoon, most of the drizzle is expected to end, leaving low
level cloud cover. Breezy warm air advection will lift temperatures
into the 50s.
Tonight, round two. A large stacked low pressure system will slide
east across the North Dakota/Canada border while its trailing cold
front slides east through the Ozarks. Ahead of the front, a
southwest to northeast oriented 35-40 knot low level jet will begin
approaching the CWA. This will cause rain showers to move into the
area beginning around midnight. Soundings continue to show 300-400
Joules of elevated instability above the inversion. This could cause
some rumbles of thunder, but nothing severe is expected. South winds
of around 10 mph with gusts to 15-20 mph are expected during the
second half of the night. This will keep temperatures from falling
too much as lows only fall into the upper 40s to mid 50s.
&&
.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 327 AM EST Sun Dec 15 2024
Monday through Tuesday Night...
Fairly progressive flow aloft is forecast across the CONUS during
this time frame. Numerous shortwave troughs will move through
within the mean flow with one affecting the region Monday and into
Monday night.
Widespread precipitation should be in progress across the region
Monday morning within a warm advection pattern/isentropic lift
regime. This activity is forecast to lift northeast during the
morning hours. Some uncertainty remains on whether we'll see any
clearing in the afternoon. Should that be the case, we'll be able
to generate a few hundred joules of surface based instability to
support at least some isolated rumbles of thunder with showers that
are expected to develop in advance of the cold front which will push
through Monday evening. In addition, any warming of the lower
boundary layer may be sufficient to mix out the 875-850 hPa inversion
that shows up on many model proximity soundings across the area.
Fairly fast flow at 850 hPa could translate down to the surface and
produce gusts Monday afternoon in the 25-30 mph range. A few gusts
of 30+ mph will be possible within convective showers.
Highs on the day look to warm into the 60-65 degree range. QPF in
the model blend tonight is a bit higher than in previous runs.
Rainfall amounts of a half to one inch will be possible south of the
WK/BG Parkways, but a solid 1 to 1.5 inches will be possible north
of the Parkways. Some isolated 2 inch amounts can't be ruled out,
especially where locally heavier showers train over areas. With the
passage of the front, cold advection will bring temps down late
Monday night with lows in the 35-40 degree range.
For Tuesday, surface high pressure is forecast to build into the
region along with some mid-level height rises in the wake of the
passing shortwave trough axis from Monday. This should result in a
dry day with highs of 50-55 north of the Parkways with 55-60 to the
south. This looks to be a fairly short dry spell as clouds will
rapidly increase Tuesday night as the next shortwave trough aloft
pushes toward the region. We'll be in a warm advection/isentropic
lift pattern once again with a warm frontal boundary lifting
northward. We'll likely see a gradient of temperature for lows
Tuesday night with upper 30s/lower 40s across southern IN and
northern KY, with low-mid 40s across southern KY.
Wednesday through Saturday...
Surface warm front should lift northward into KY during the day on
Wednesday with a weak surface low pushing northeast from the TN
Valley into the northern OH valley with yet another cold front
coming through. Most of the precipitation on Wednesday looks to be
in the morning with a fairly rapid decrease in the afternoon.
Another round of light to moderate rainfall is expected here and
another half to one inch of rainfall is forecast. Some minor
flooding could occur in spots that receive ample rainfall earlier in
the week, along with rises on area creeks and streams. Highs
Wednesday will range from the low-mid 50s over southern IN and
northern KY to the upper 50s/lower 60s over southern KY. Cold
advection will once again bring much colder temps behind this front
for Wednesday night. Lows look to dip into the 25-30 degree range.
Overall dry conditions are likely for Thursday, but much colder
temperatures are expected. Highs Thursday will be in the upper 30s
to the lower 40s, with lows in the upper 20s. Will be watching
Friday closely as the upper level pattern will be amplifying with a
large trough in the eastern US with strong ridging developing out
west. This fits pretty well with the MJO transitioning to phase 6,
which in a La Nina year would favor the bulk of the cold staying to
our north, but we'll see below average temps for Friday and Saturday
locally. As the pattern amplifies, a weak perturbation may roll
through here on Friday bringing some light snow showers/flurries.
GFS and the GEM agree on this, while the Euro is much drier.
Current blended temps are likely too warm for Friday with highs in
the lower 40s. I suspect this warmer blend is too influenced by the
warmer Euro contributions. More than likely, we'll see temps about
5-10 degrees colder here. Lows Friday night should dip into the
upper teens to the lower 20s. Highs Saturday look to be in the
lower 30s.
&&
.AVIATION /12Z TAFS THROUGH 18Z MONDAY/...
Issued at 653 AM EST Sun Dec 15 2024
The rain is on its way out as it works east through the region.
Ceilings are currently lowering into MVFR levels, and they are
expected to continue to fall into IFR levels. Don't believe
visibilities will be much of an issue today. Tonight, our next
system moves in from the west. This is expected to bring widespread
IFR ceilings. Reduced visibilities are expected to arrive Monday
morning.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...KDW
LONG TERM...MJ
AVIATION...KDW
Source:
LMK issues Area Forecast Discussion (AFD) at Dec 15, 6:53 AM EST ...Updated Aviation Discussion...---------------
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