LMK issues Area Forecast Discussion (AFD) at Dec 2, 12:46 PM EST ...Updated Aviation Discussion...428
FXUS63 KLMK 021746
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1246 PM EST Mon Dec 2 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Scattered light snow and flurries are possible this afternoon and
evening. Snow accumulations of a dusting to half an inch are
possible.
* Temperatures well below normal for much of this week, with
overnight lows in the teens to 20s. Daytime highs will be limited
to the 30s every day, except for Wednesday.
&&
.UPDATE...
Issued at 1023 AM EST Mon Dec 2 2024
At this hour, water vapor imagery shows the mid-level shortwave
trough axis approaching the Quad Cities area as it moves from
northwest to southeast across the Midwest. Over the past 90 minutes
or so, a general increase in reflectivity area and magnitude has
been noted across central Illinois, with ASOS/AWOS obs and traffic
cameras confirming pockets of light to moderate snow. This area of
snow extends a bit farther north than anticipated, and hi-res
guidance has trended a bit north with the measurable QPF swaths
later today. With that being said, latest SDF ACARS soundings show
sub-saturation from the sfc up to around 700 mb, and upstream obs do
suggest that the initial wave of radar returns is not making it to
the ground. As this wave approaches Kentucky and Indiana later
today, clouds are expected to increase, with flurries and light snow
showers expected this afternoon and evening. If the current trends
continue, PoPs may need to be adjusted upward across the northern
half of the FA, although expected QPF and snow amounts will still be
light. Otherwise, the current forecast is on track; will send
updated products here shortly with updated near-term T/Td.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 326 AM EST Mon Dec 2 2024
Synopsis...Rex Block will consolidate over the Western CONUS while
longwave trough and broad cyclonic flow remains anchored over the
Central and Eastern CONUS. A shortwave trough, currently moving from
southern Canada to the Upper Midwest, will strengthen as it
continues traveling southward to then swing by the Ohio Valley later
today and tonight. At the surface, an area of low pressure will
accompany the system and track across the Lower Tennessee Valley
with strong continental high pressure dropping along the Mississippi
later tonight.
This Morning...Satellite water vapor imagery clearly shows the mid-
level shortwave trough moving across Minnesota with associated
moisture plume extending ahead to Iowa and Missouri. This mid-level
cloud deck should arrive to the forecast area later this morning. As
a result, there will be a decent window of clearing skies this
morning for temperatures to drop to the teens and low twenties. Only
caveat to achieve the forecast lows is a low-level cloud deck that
is slowly moving eastward across the Bluegrass. Otherwise,
anticipated dry weather through the morning hours with light
westerly winds.
Afternoon & Evening...Cloud thickness and coverage will increase
during the afternoon hours as the mid-level wave approaches the
region. GFS forecast soundings depict top-down saturation as the
limited moisture connected to the wave overspreads the area. DGZ
saturation and acceptable 850-700 mb lapse rates will be present on
the western half of the forecast area after 18Z so that some
flurries could be reported. The most likely scenario, however, is a
dry forecast through 20Z given the dewpoint deficits in the low
levels leading to evaporation and further top-down saturation.
Perhaps the biggest change with the current forecast package is a
delay of the light snow onset, expected now between 2/21Z and 3/0Z.
On the other hand, deterministic guidance continues to hint at
snowfall amounts of 0.1 to 0.2 inches with higher localized totals
of 0.3-0.5 inches, mainly across south-central Kentucky. Little to
no impacts are anticipated based on light snow rates and pavement
temperatures above the freezing point.
Tonight...Light snow chances will end from west to east between 3/3-
6Z with gradual clearing towards sunrise. Surface high pressure will
continue favoring cold air advection and temperatures well below
average for this time of the year (10s and low 20s). Only concern
for the overnight hours is the possibility of slick roads along
south-central Kentucky due to refreezing of melted snowfall.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 326 AM EST Mon Dec 2 2024
Tuesday - Tuesday Night...
Cold NW flow will be in place Tuesday morning, with a strong
Canadian-sourced sfc high centered over Missouri. This sfc high is
forecast to slide southeast over the Tennessee Valley on its way to
Georgia by 12Z Wednesday. Mid-level shortwave ridging will nose over
the Ohio Valley on Tue, and fcst soundings show plenty of dry air.
Expect a mostly sunny, but chilly day with afternoon temperatures
only rebounding into the mid 30s.
As the high slides off to the southeast Tuesday night, SW flow WAA
kicks into gear ahead of a cold front cutting southeast through the
Upper Midwest and central Plains. A deepening low pressure system is
forecast to dive southeast over Canada. Increasing SW sfc winds late
Tue night and Wednesday morning will result in earlier overnight
lows. Temps should drop off readily Tuesday evening, with lows in
the upper teens to lower 20s for most. The temperature curve should
flatten and even begin rising early Wednesday morning.
Wednesday - Wednesday Night...
A strong low pressure system will rotate southeast over Ontario and
SW Quebec Wed and Wed night, dragging a cold front through the Ohio
Valley. The strongest mid/upper level ascent and deepest moisture
will remain off to the northeast over the Great Lakes and Northeast.
Moisture depth could be just sufficient enough to squeeze out a
hundredth or two Wednesday night, but confidence in measurable
precip is low.
Ahead of fropa, Wednesday looks warmer (but still chilly) than
Tuesday and windy. Gusts over 30 mph will be possible, helping to
keep wind chills largely in the 30s. Actual air temperatures,
however, are forecast to rise into the mid/upper 40s Wednesday
afternoon. Think the cold front passes through mostly dry Wednesday
night, but it will bring another shot of cold air to the region.
Temperatures are forecast to drop into the 20s to lower 30s Thursday
morning.
Thursday - Sunday...
Another cold high pressure system is forecast to slide southeast
over the Mid-MS and Lower OH Valley Thursday and Friday. Temps
Thursday will struggle with strong CAA. Currently have highs ranging
from the upper 20s to mid 30s. A stout 10-15 mph breeze out of the
NW will result in wind chills in the teens to 20s.
Winds are forecast to gradually diminish Friday morning as the sfc
high approaches western KY. With skies currently expected to remain
mostly clear, conditions look pretty favorable for radiational
cooling. This forecast calls for lows in the 13-18 degree range
Friday morning. Temperatures should rebound into the mid 30s Friday.
The latest suite of model guidance diverges on the basics of the
synoptic scale pattern over the weekend. Temperatures are likely to
moderate this weekend into early next week. Confidence in
precipitation chances and timing is very low.
&&
.AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 1245 PM EST Mon Dec 2 2024
Impacts:
- Light snow showers bringing MVFR/IFR visibilities this afternoon
and evening (medium confidence)
- MVFR ceilings this evening, potentially lingering overnight into
early Tuesday morning (medium-high confidence this evening, low-
medium confidence on duration)
Discussion: A quick-moving system will pass across the area this
afternoon and evening, with moisture building down as we head later
into the afternoon. Patchy flurries should transition into light
snow showers from west to east this afternoon, with upstream obs
generally showing IFR or MVFR visibilities from snow. However, it is
expected that these snow showers will not be as strong by the time
they reach local terminals, so will advertise MVFR VIS. As snow
showers are ending this evening, ceilings are expected to drop to
MVFR levels, with cloud bases around 2 kft. It is uncertain just how
fast these clouds will clear out tonight, and have gone a bit more
pessimistic/slower with this forecast issuance. Winds will remain
relatively light through the forecast period, generally from the
W/NW. VFR conditions are expected to return by the end of the
forecast period on Tuesday.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...CSG
SHORT TERM...ALL
LONG TERM...EBW
AVIATION...CSG
Source:
LMK issues Area Forecast Discussion (AFD) at Dec 2, 12:46 PM EST ...Updated Aviation Discussion...---------------
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