LMK issues Area Forecast Discussion (AFD) at Feb 10, 12:27 AM EST ...Updated Aviation Discussion...789
FXUS63 KLMK 100527
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1227 AM EST Mon Feb 10 2025
...Updated Aviation Discussion...
.KEY MESSAGES...
* Cool and mostly dry conditions expected today through Monday.
* Potential for a winter storm continues to increase for Monday
night through Tuesday evening. Forecast confidence for
significant snowfall accumulations in the area between I-64 and
the WK/BG Parkway continues to increase. A Winter Storm WATCH
has been issued for this time period. Light icing may also become
a factor Tuesday night across the Bluegrass.
* Additional chances for precipitation Wednesday Night and
Thursday, as well as next weekend, will lead to an enhanced
potential for flooding across the area.
&&
.UPDATE...
Issued at 1026 PM EST Sun Feb 9 2025
Current satellite and observations show mid-high level cloudiness
streaming across the region. Temperatures are in the mid 30s across
the region. Current forecast for the overnight period remains on
track with lows dipping into the upper 20s to the lower 30s.
Moving toward the Monday night and Tuesday period, the 18Z guidance
came in with some higher snowfall totals across the north. The NAM
was on the northern edge of the guidance and the GFS was the most
south of the guidance. The 18Z Euro was right in the middle of the
NAM and GFS snow swaths. The 00Z NAM solutions came in even more
impressively with stronger dynamical forcing along with heavier QPF
values. In those NAM solutions, we can see a good period of solid
wetbulbing Tuesday morning which should result in snow being the
primary p-type. Additionally, a colder northeast surface flow looks
to keep the column just cold enough to keep snow going through much
of the day.
There remains uncertainty on the northward push of moisture into
southern Indiana and how far north the warm nose will get. Current
thinking is that some warmer air aloft will get into portions of
central KY which may result in a wintry mix of sleet and possibly
freezing rain as discussed in the previous forecast. A band of
heavy snow is likely to develop somewhere between the I-64 corridor
and the WK/BG Parkways. Current thinking is that the area along and
just north of the WK/BG Parkways may be the sweet spot. Given the
increasing snow amounts and trends, have coordinated with JKL and
issued a Winter Storm Watch for southern IN and north-central and
east-central KY. There is some uncertainty on the northern and
southern edges of this watch area. However, those uncertainties
should decrease over time and an upgrade to winter weather
advisories and winter storm warnings will be forthcoming in future
forecast issuances.
Further south, profiles are warm for a cold rain across southern KY.
Model QPF amounts of 1-2 inches will be possible. Our lowest FFG
values are down across this region. Given the recent excessive
rainfall over the past few days along with this forecast additional
rainfall, have also coordinated with JKL to issue a Flood Watch for
southern KY. This watch will likely be extended in time with future
issuances to cover additional heavy rain threats for later this week
and possibly into the weekend.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 303 PM EST Sun Feb 9 2025
Through This Evening... A weak wave is moving through the southern
portion of the region, bringing lift to very shallow moisture around
700mb. Precip developing will fall through a dry layer around 850mb
which will allow for evaporation. As these showers move across the
region, could see very light rain or drizzle in the southern portion
of the region through 0Z. The low-level cloud deck has nearly mixed
out, and broken stratocu has been building in behind the cloud deck.
Tonight and Monday... Surface high pressure and dry air aloft will
push into the region from the northwest. This allow skies to thin
and lift in the early evening. Light northerly winds will steadily
veer to the northeast overnight, as high pressure approaches the
region. Temperatures are expected to cool into the mid to upper 20s
and low 30s in southern Kentucky.
With zonal flow aloft, Monday will remain quiet and mild. High
temperatures will warm into the low to mid 40s along and north of I-
64 and mid to upper 40s south of I-64.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 303 PM EST Sun Feb 9 2025
Monday Night - Tuesday Night...
High pressure will be in place over the Upper Ohio River Valley
region to start Monday night, and we expect initial dry and cool
conditions. Things are expected to deteriorate as we get later into
Monday night and Tuesday as the first in a series of waves impacts
our region. The overall setup features a broad and elongated
baroclinic zone from the Red River Valley up through the central
Appalachians and through the mid Atlantic. Shortwave troughing looks
to eject out of the SW CONUS, with deepening moisture riding ENE
along an initial inverted surface trough to our south and east.
We'll be situated beneath the favorable right entrance region of a
150 knot upper level jet and a moderate, but deep, poleward sloping
frontogenetical component. As mentioned in the previous discussion,
we'll have cold air in place across the northern half of our CWA
thanks to the surface high pressure to our NE, and it seems to hold
its ground fairly well against the warm nose. As a result, forecast
soundings show a saturated column by early Tuesday with a deep
isothermal layer just below the 0C line. This would yield a wet and
low ratio snow given the current profile, but given the
frontogenetical component we will likely have some banded features.
Time height cross sections reveal some vertical theta e surfaces
through the saturated DGZ, which yields some slightly negative EPV
values. The end result looks to be periods of WSS/CSI capable of
stronger bands of snowfall. Once we get into the range of the HREF,
will be looking for some probabilities of 1" per hour rates before
we can nail down what to expect from what will likely be a narrower
corridor of higher snowfall totals. The 12z run of the HREF does
show a 10-20% chance of 1" per hour rates across central KY up
through 12z Tuesday, and expect we'll get a clearer signal with the
next run as it goes past 12z Tuesday and into the heart of the
event.
Right now, a pretty broad 1 to 3" snowfall is expected north of a
Hartford, KY to Stanford, KY. Across southern IN, totals are also
expected to be lessened due to the limited northward extent of the
deep moisture, and right now any heavier band looks to be located
somewhere between the Ohio River and that line mentioned above.
We'll likely need a Winter Weather Advisory given the current
forecast, and can't rule out more significant headlines over narrow
corridor if the frontogenetical component does look to yield a swath
of higher amounts. Gotta say, the time heights and associated
frontogenetical component were a bit more impressive than I
expected, and could still get a decent swath of snow even with 7 or
8 to 1 SLRs.
Do think there could be a brief period of sleet for some across
central KY as soundings do show the warm nose trying to edge in
weakly. This could cut into totals on wherever the southern end of
the snow line is, with a pretty solid transition to rain across
southern KY. Have also noted that we lose saturation aloft as we go
into Tuesday night, so there could be a period of freezing
rain/drizzle to end the event across our northern CWA. Something to
watch for. Will carry some light accums in our Bluegrass region
Tuesday night.
It is also worth noting that we will likely see another 1 to 2" of
rain across southern KY which could lead to some minor flood
concerns, and agitate rivers that are already running above normal.
After collaborating with WPC/JKL/ILN about a Winter Storm Watch we
decided to hold off for now. Most likely area for perhaps a narrow
watch/warning would be along the I-64 corridor east of I-65, but
want to see a consistent trend in data before committing to that
given the tight gradient.
Wednesday - Thursday...
We'll see a brief break in activity on Wednesday, however another
system quickly arrives by later Wednesday into Thursday. This setup
features some degree of phasing between a weaker northern stream
system, and more moisture laden southern stream impulse. The end
result appears to be strengthening cyclogenesis over our CWA, with
the surface low cutting more poleward as it moves through. The end
result should be a slightly milder system, assuming models have a
good handle on the timing/degree of the phase. We'll continue to
call for mostly rain with this one, with another .5" to 1.5" across
our southern CWA. In addition, we'll have to consider additional
melt of any lingering snowfall across northern and central CWA.
Luckily, rainfall amounts are expected to be less than an inch in
these areas. Any aggravated rivers, and ongoing saturated soils
could be worsened by this 2nd round of rainfall. Flood watches are
pretty likely to be issued at some point, and it could come as early
as the first wave of precipitation across southern KY. Farther
north, it is more likely to come with the second or third wave.
Thursday Night - Friday Night...
We do get a slightly more prolonged break from precipitation to end
the work week as high pressure briefly takes hold and the surface
front sags well to the south. Thursday night looks cold with lows in
the teens to around 20. Could have some decent recovery on Friday
with highs back in the 40s to near 50. A milder night follows on
Friday night as increasing cloud cover keeps temps up ahead of the
next approaching system.
Saturday - Sunday...
For now, the weekend system has a concerning look as a more potent
shortwave trough ejects out of the western CONUS, and a stronger
surface low develops and strengthens near our region. This will
allow the system to draw on very deep moisture (likely the strongest
of the 3 waves). Looks to be too mild for any wintry precipitation,
and hopefully the surface low track doesn't trend northward. That
would bring severe weather into play. Unfortunately, the current
track does suggest another round of widespread rainfall, and could
be moderate to heavy at times. Current data suggests another 1.5" to
3" of rainfall across southern KY, with an inch or less across our
northern CWA. Do have concerns that this final wave could send us
closer to some more widespread and impactful flooding, so have
decided to issue an ESF, and will also include that info in a hydro
discussion as well. There is concern for many of our river basins,
especially if the 3rd wave is a potent as it currently appears.
Overall, liquid precipitation amounts now through Sunday look to
range from 2 to 6", locally up to 7". Highest totals will likely be
southern CWA, with the lighter amounts most likely across southern
IN. Stay tuned.
&&
.AVIATION /06Z TAFS THROUGH 12Z TUESDAY/...
Issued at 1224 AM EST Mon Feb 10 2025
VFR conditions are present across area terminals at this hour and
are expected to continue through much of the current forecast
period. There are a few patches of lingering MVFR stratus over
central IN and southwest OH which model guidance tries to bring
toward LEX/RGA/BWG around 12Z today. Since this is fairly patchy
right now, will take MVFR CIGs out of the forecast for now and
monitor obs through the morning hours. Otherwise, broken high clouds
and light northeast winds are expected later today. Ceilings will
begin to decrease again toward the end of the current forecast
period as an area of low pressure moves toward the region late
tonight.
&&
.HYDROLOGY...
Issued at 303 PM EST Sun Feb 9 2025
Rounds of Widespread Rainfall Continue Through This Week...
An unsettled pattern of weather is expected through this week with
three separate storm systems expected to track through our region.
The first system will move through late Monday night through Tuesday
night, bringing a wintry mix across southern Indiana and northern
Kentucky. Mostly rain is expected across southern Kentucky where 1
to 2" of rain could occur.
The second storm system is expected later Wednesday through
Wednesday night, and is expected to be mostly rain. An additional 1
to 2" of rain is expected with this system, especially across
central and southern KY once again. We'll also have to keep in mind
how much additional liquid may still need to melt off from the
earlier snow across central and northern KY.
A third, and potentially the strongest, system then arrives through
Saturday through Sunday where 1 to 3" of rain is currently forecast.
Central and southern KY are currently expected to see the higher
totals out of this wave as well. Overall, total rainfall amounts
through next Sunday could range between 3 and 7" across central and
southern KY, with 2 to 3" expected across southern Indiana and far
north central KY.
With already saturated soils, and area rivers and streams continuing
to run high, these waves of rain will likely make flash flood and
river flood threats increase as we move through the week. The river
basins that stand the biggest threat of widespread minor flooding,
and perhaps higher impacts, would be the Green, Rough, Rolling Fork,
Cumberland, Kentucky, and Licking. The Ohio River will also see
notable rises with added rainfall and contributions mostly from
southern tributaries. Stay up to date of the latest forecasts during
this active and potentially impactful stretch of weather.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...Winter Storm Watch from this evening through Wednesday morning
for KYZ023>043-045>049-053>057.
Flood Watch from this evening through Wednesday morning for
KYZ061>067-070>078-081-082.
IN...Winter Storm Watch from this evening through Wednesday morning
for INZ076>079-083-084-089>092.
&&
$$
UPDATE...MJ
SHORT TERM...SRW
LONG TERM...BJS
AVIATION...CSG
HYDROLOGY...BJS
Source:
LMK issues Area Forecast Discussion (AFD) at Feb 10, 12:27 AM EST ...Updated Aviation Discussion...---------------
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