LMK issues Area Forecast Discussion (AFD) at Nov 28, 3:12 AM EST
594
FXUS63 KLMK 280812
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
312 AM EST Thu Nov 28 2024
.KEY MESSAGES...
* Cool and cloudy Thanksgiving with patchy drizzle in the morning.
* Unseasonably cold temperatures are expected Friday through the
first half of next week.
* Minor snow accumulations are possible Saturday night.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 311 AM EST Thu Nov 28 2024
Synopsis...Upper-level low will meander around the Quebec/Ontario
borderline while pronounced mid-level shortwave troughs cross the
Ohio Valley. The first of these waves will depart the region early
this morning after bringing light rain showers and starting cold
advection regime. The second wave will arrive later tonight and
although it likely won't be associated with precipitation, it will
certainly reinforce cold air advection and well below normal
temperatures this weekend.
Model Evaluation/Confidence...Overall, forecast confidence during
this period is relatively high with minor differences arising
Thursday night regarding the possibility of some flurries as lifting
from the second wave and crashing temperatures catch up with the
exiting stratus layer. However, after consulting available guidance
it seems that the deterministic CMC and some of its ensembles are
the ones heavily supporting flurries Thursday night while the ECWMF
and GFS deterministic/ensembles remain dry. Given past experiences
with the CMC being overexcited about snow potential, relied on the
GFS/ECMWF output.
This Morning...Current surface observations locate the slowly-
deepening surface low pressure close to exit the state while the
cold front is draped southward across eastern Kentucky and into
Tennessee. As a result, central Kentucky and southern Indiana is
experiencing postfrontal northwest winds and lowering air
temperatures amid light rain chances as the previously-enhanced 700-
mb frontogenetic band has since weakened. Precipitation chances will
slowly decrease towards dawn with rain as the main p-type with
minimal chances of wet snowflakes in southern Indiana during the
next hours. In any case, pavement temperatures will continue to be
above freezing.
Today...Forecast soundings indicate top-down drying trend this
morning but with enough saturation in the lowest layers to support
patchy drizzle the first morning hours. Cloudy skies will linger the
rest of the day along with a subtle west-northwest winds. Cold air
advection and lack of solar radiation will account for well below-
normal highs in the low to mid 40s with feel-like temperatures
probably in the upper 30s.
Tonight...A west-to-east clearing trend will take place as even
drier and colder air approaches from the Midwest with the second
shortwave impulse. Lows will finally fall below the freezing point
and into the mid to upper 20s with the coldest spots several degrees
lower. As mentioned above, some of the guidance is favoring a chance
of flurries (especially east of I-65 where the clouds will linger
longer), but leaned towards a precip-free forecast following model
consensus and known biases.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 311 AM EST Thu Nov 28 2024
Several days of unseasonably cold weather are expected, as the upper
pattern will be marked by a broad eastern CONUS trof around a deep
closed low initially over James Bay. A series of sfc highs will drop
SE from the Dakotas into the Deep South to keep reinforcing the cold
air.
We'll be dry Friday and the first part of Saturday under the first
of those high pressure centers, with temps around 15 degrees below
normal for the end of November.
A Clipper shortwave will swing across the central Plains into the
Ohio Valley Saturday and Saturday night, but the forcing is modest
and the sfc reflection almost nonexistent. Still it looks like it
squeezes out just enough moisture to overcome the low-level dry air
and produce minor snow accumulations on Sat night. Confidence in
this system is limited mainly by how much can actually reach the
ground, and that is reflected in the POPs still only around 50
percent. Minor snow accumulations are possible given that precip
will occur at night with temps in the mid/upper 20s. Amounts should
be less than 1 inch, but will continue to monitor this system
through upcoming forecast cycles.
Closed low over eastern Canada opens up late in the weekend, but
persistent NW flow aloft will allow the cold to stick around. Temps
start to moderate by Wednesday with another Clipper mainly passing
to our north and east. POPs limited to the 20-30% range as
confidence is low regarding any precip this far south and west.
&&
.AVIATION /06Z TAFS THROUGH 12Z FRIDAY/...
Issued at 1227 AM EST Thu Nov 28 2024
Impacts/Confidence:
- High confidence in IFR ceilings through the morning hours
- Medium to high confidence confidence in LIFR ceilings and IFR
visibilities with light rain showers before sunrise
- MVFR ceilings and northwest light breeze into the afternoon
Discussion...Surface low pressure center is currently moving across
eastern Kentucky while a cold front extends southwestward into south-
central Kentucky. Subtle northwest breeze is observed behind the
frontal line along with light rain showers. IFR to LIFR ceilings as
well as IFR visibilities will accompany the light rain activity
through the coming hours. Then, a change to light drizzle as the
main precipitation type and better VIS is expected right around
sunrise based on drying trend aloft. Overall, conditions will
improve late this morning and especially during the afternoon as dry
weather returns and the base of the clouds lift to VFR thresholds.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
SHORT TERM...ALL
LONG TERM...RAS
AVIATION...ALL
Source: LMK issues Area Forecast Discussion (AFD) at Nov 28, 3:12 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202411280812-KLMK-FXUS63-AFDLMK)
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