LMK issues Area Forecast Discussion (AFD) at Feb 18, 11:38 AM EST
556
FXUS63 KLMK 181638
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1138 AM EST Tue Feb 18 2025
.KEY MESSAGES...
* Light snow will cause travel problems this morning in southern
Indiana and north central Kentucky. A Winter Weather Advisory is
in effect this morning in southern Indiana and north central
Kentucky generally along and north of a line from Hawesville to
Bardstown to Winchester, including Louisville and Lexington.
* An impactful winter storm is forecast to produce significant snow
accumulations tonight through tomorrow morning. A Winter Storm
Warning remains in effect for areas generally south of I-64, with
a Winter Weather Advisory to the north. The heaviest
accumulations are expected in a 2-3 county wide band from
Hartford and Morgantown over to Liberty and Stanford.
* Very cold temperatures are expected after the winter storm. Wind
chills below zero will be possible Thursday morning.
&&
.UPDATE...
Issued at 1138 AM EST Tue Feb 18 2025
Thumping snow band has diminished considerably in the last hour as it
heads east-southeast along and south of the I-64 corridor. HRRR and
RAP solutions were indeed correct here with that diminishing trend.
We've had about an inch of snow in the Louisville metro region with
this band. Impacts are subsiding rapidly as webcams and traffic
data show the main roads in good shape and parking lots and side
streets around the office have improved rapidly with the onset of
drier conditions. For the remainder of the morning, we'll continue
to see some light snow lingering across southern IN in the I-64
corridor with flurries to the north/south of that region. The
heaviest snow will continue to push eastward into the Bluegrass
region. A quick quarter to perhaps a half inch will be possible on
untreated surfaces and grassy areas. Will let Winter Weather
Advisory ride though expiration if current trends hold up.
For the afternoon, we expect a break in the precipitation as we
await the main show this evening.
Updated 1011 AM EST Tue Feb 18 2025
Current snow band continues to chug along to the east while drifting
southward over the last hour. The band currently has shifted south
of the I-64 corridor and stretches from Perry county IN eastward
through northern Meade/southern Harrison and into the southern
Louisville and northern Bullitt county area. The band also
continues eastward down the I-64 corridor into the Lexington metro
area. We've also seen the snow fill in a bit across portions of
Breckinridge and into central parts of Hardin county.
The band is largely driven by strong low-level frontogenesis. This
can be seen by looking at the low-level thermal gradient with 10
degrees in Bloomington to around 20 degrees along the Ohio River.
The efficient lift along with a slight isentropic component is
really wringing out the moisture we have in the column.
Overall, the impacts have been light to moderate. Area webcams show
the main roads are remaining fairly clear given the volume of
traffic and ongoing treatments. Parking lots, side streets and less
traveled secondary/back roads are likely snow covered within this
snow band. Quarter to half inch snow amounts have been reported with
a recent report of 0.6 inches in Ferdinand, IN.
The latest data continues to show this band transitioning eastward
with time and diminishing rather quickly. Not sure I buy how fast
the RAP/HRRR are diminishing this. Perhaps the NAM3k may be a bit
better showing this band shifting east-southeast down the I-64
corridor between Louisville and Lexington this afternoon while
weakening as stronger forcing departs the region.
Updated at 843 AM EST Tue Feb 18 2025
Within the last hour, the snow band has organized a bit more mainly
just north of the I-64 corridor. Moderate snow extends from Dubois
county through southern Orange and Crawford counties in southern IN.
This band also extends further downstream into southern
Washington/Floyd and Clark counties and into Oldham/Henry counties.
Some smaller bands were transversing the Louisville metro area and
this activity is likely to increase over the next hour.
Lighter snows have been trying to develop a little more southward
into Meade, far northern Hardin and into Bullitt/Spencer counties.
This slow southward progression is likely to continue as well, along
with spreading downstream back into the Lexington metro.
Latest high resolution models suggest this snow activity should
diminish in the 11-noon EST time frame. However, in the meantime,
the snow will accumulate on lesser traveled roads and untreated
roads across the region, resulting in hazardous travel. Snowfall
amounts of a quarter to half inch are likely. A stripe of 1 inch
snowfall is very possible right along the I-64 corridor where
heavier bands transverse this area.
Updated at 737 AM EST Tue Feb 18 2025
Banded light snow continues this morning, mainly north of the I-64
corridor across southern Indiana. The most intense bands have been
across far northern Harrison, Floyd, and central Clark counties in
southern Indiana and then over into northeastern
Jefferson/Oldham/Henry counties in north central KY. Other bands of
heavier snowfall will likely move through our northern row of
southern Indiana counties (Dubois, Orange, Washington, Scott, and
Jefferson). Here a quick half inch to perhaps an inch could fall
this morning.
Temperatures across the region are in the upper teens to the lower
20s. As a result, the light snow is sticking to the roads and
creating slick spots. Traffic has been most impacted on the
northern side of the Louisville metro area, mainly across southern
Indiana in Floyd and Clark counties. To the south of Louisville,
not much snow has fallen as of this writing. It appears that we may
a bit more low-level dry air in place which may be preventing any
snow from falling. There have been some stronger returns showing up
from Henderson over to Evansville that are moving east. However,
webcams and surface observations do not show much in the way of
snow hitting the ground with that activity.
For now, will keep the Winter Weather Advisory going. Depending on
activity to the west, we may be able to trim the southern edge of
this first advisory back if snowfall does not materialize.
Otherwise, latest model data suggests that this snow across southern
IN will continue for several more hours, before lift and moisture
depart the region.
&&
.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 302 AM EST Tue Feb 18 2025
Banded light snow is expected to cross southern Indiana and north
central Kentucky this morning. Though overall totals will be less
than an inch, there is some indication that fgen bands of heavier
snow may set up within the broader area of lighter snow. If these
bands do materialize, they would be capable of visibilities below 1
mile and rates strong enough to cause issues on area roadways,
especially along the I-64 corridor around or just after the morning
rush. So, while confidence in this set-up isn't very high, went
ahead with a low-end advisory for a few hours this morning to
account for the possibility of a heavier band of snow potentially
causing problems. The advisory can be dropped early if it looks like
impacts will be minimal.
This afternoon will be dry as we sit between systems. High
temperatures will mostly be in the 20s, though areas near the
Tennessee border will see readings peaking around the freezing mark.
Snow will envelop the region tonight as a lead 500mb shortwave
trough approaches the region from the west while a very strong
surface high centered over the Dakotas continues to feed frigid air
into the district. The best areas of slightly negative EPV, upper
level divergence, and poleward-sloping frontogenetical forcing line
up over central and southern portions of central Kentucky, exactly
where the Winter Storm Warning has already been placed. The heaviest
snowfall rates are expected between midnight and dawn tonight/early
tomorrow morning with the co-occurrence of the deepest RH and best
isentropic upglide on the 290K surface. Slightly gusty winds to
around 15-20 mph will add to the wintry conditions. Definitely a
good night to stay in if you can.
No doubt about precipitation type tonight as surface temperatures
tumble into the teens, resulting in a dry, high SLR snow, and
sounding progs show deep saturation throughout the DGZ.
Tomorrow the lead shortwave trough will push off to the east,
putting an end to the heavy snow. The parent upper low will then
settle southeastward across the Midwest and may help to generate
additional flurries or light snow showers in the mid/late afternoon,
but a dry slot moving in will limit moisture supply. High
temperatures will be in the 20s.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 302 AM EST Tue Feb 18 2025
===== Additional Snow Showers Wednesday Night =====
Most of the moisture associated with the winter storm will be
departing to the east by Wednesday night. However, the large upper
low will still be spinning over the Great Lakes, with the trough
axis swinging through the Ohio Valley by Thursday morning. A
secondary mid-level vort max pinwheeling around the low will bring
another round of moisture to the region Wednesday night, and
combined with the forcing at play, should produce some snow showers
across the area. Moisture will not be nearly as favorable as the
earlier system, but soundings show steep low level lapse rates and
saturation through the DGZ. It's possible some snow showers could
have a squall characteristic to them, but the snow squall parameter
remains quiet for our area. An additional 0.5 inch is most likely,
though some guidance is coming in with 1 inch swaths possible. High
snow ratios around 20:1 add to the confidence of some areas seeing
another inch of snow Wednesday night into Thursday morning. The
trough axis and associated moisture layer will depart off to the
east by sunrise Thursday morning.
===== Drier Weather Thursday - Friday =====
* VERY COLD WEATHER LATER THIS WEEK *
Strong Canadian sfc high pressure will drop into the central Plains
on Thursday, which will provide a strong CAA regime and NW flow into
the Ohio Valley for the end of the week. Temps Thursday morning will
be very cold as arctic air will be filtering in. Temperatures in the
single digits west of I-65, and lower teens to the east, are
forecast. As mentioned in the previous discussion, sfc winds are not
expected to be particularly strong on Thursday, but given the bitter
sfc temps, wind chills are likely to be near or below zero for most
of the area Thursday morning. The ECMWF Extreme Forecast Index
continues to really key in on Thursday and Friday for both min and
max temps, with high confidence for anomalously cold temperatures.
Forecast highs for Thursday will struggle to get above 25F. The good
news, though, is that we should see the lingering cloud deck depart
through the day, and should have some sunshine by the afternoon
hours.
For Thursday night and into Friday, the sfc high pressure will be
shifting eastward and closer to the area. This will allow for the
best radiational cooling night of the period, with temps in the
single digits for the entire area. It will be quite possible that
the areas that have the deeper snow pack from the winter storm could
be even colder, possibly below zero. Despite the colder
temperatures, the lighter winds Friday morning will likely allow
wind chills to not be as cold as Thursday morning. Cold weather
headlines will be something to consider later this week.
Upper ridging combined with the sfc high directly overhead will help
temperatures rise to near the freezing mark on Friday. Light winds
and mostly sunny skycover will help make it feel like a nice day.
===== The Weekend Discussion =====
There continues to be a signal for a weak system to pass through
over the weekend. The GFS remains slightly later than the ECMWF,
though there is a bit more temporal agreement. They both hint at
Saturday precip, though there is still some difference on timing
during the day. Thermal profiles continue to suggest wintry precip,
but moisture will be really sparse and impacts seem unlikely at this
time. The NBM keeps us dry for the period, with a silent 10% PoP the
only indication of any the weekend wave. Will continue with this NBM
solution for now given the lack of moisture expected.
Temps for the weekend will also climb back to near normal, with
highs in the upper 30s on Saturday, and 40s on Sunday.
&&
.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 622 AM EST Tue Feb 18 2025
A band of light snow from central Indiana to southeast Kansas will
slide ESEwd across the northern TAF sites this morning, especially
SDF and HNB, resulting in MVFR vis/cigs. Can't rule out sub-MVFR
visibilities in any narrow heavier snow band that might set up,
especially at SDF and HNB between 13 and 16Z, but such conditions
would be brief and models have backed off a bit on this idea
compared to earlier, so will refrain from putting anything that
restrictive in the TAFs for now. Most upstream vsbys at this time
are no worse than MVFR.
We'll get a break this afternoon behind this morning's light snow.
Then the main show will arrive this evening and continue into early
Wednesday morning as an upper trough approaching from the west
spreads snow into the region. The worst flying conditions will be
between midnight and dawn late Tuesday night/early Wednesday morning.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Weather Advisory until 1 PM EST /noon CST/ this
afternoon for KYZ023>025-028>043-045>049.
Winter Weather Advisory from 7 PM this evening to noon EST
Wednesday for KYZ030>037-042-043.
Winter Storm Warning from 7 PM EST /6 PM CST/ this evening to
noon EST /11 AM CST/ Wednesday for KYZ023>029-038>041-
045>049-053>057-061>067-070>078-081-082.
IN...Winter Weather Advisory until 1 PM EST /noon CST/ this
afternoon for INZ076>079-083-084-089>092.
Winter Weather Advisory from 7 PM this evening to noon EST
Wednesday for INZ076>079-083-084-090>092.
Winter Storm Warning from 6 PM this evening to 11 AM CST
Wednesday for INZ089.
&&
$$
UPDATE.......MJ
SHORT TERM...13
LONG TERM....CJP
AVIATION.....13
Source: LMK issues Area Forecast Discussion (AFD) at Feb 18, 11:38 AM EST (https://mesonet.agron.iastate.edu/p.php?pid=202502181638-KLMK-FXUS63-AFDLMK)
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