LMK issues Area Forecast Discussion (AFD) at Dec 11, 12:59 PM EST ...Updated Aviation Discussion...335
FXUS63 KLMK 111759
AFDLMK
Area Forecast Discussion
National Weather Service Louisville KY
1259 PM EST Wed Dec 11 2024
...Updated Aviation Discussion...
.KEY MESSAGES...
* Scattered snow showers and snow squalls are expected this
afternoon and evening. Light snow accumulations will be
possible in spots. With possible whiteout conditions from
snow squalls during the evening commute.
* A wet weekend is in store with widespread showers, especially
Saturday afternoon and evening.
* No snow in the forecast Thursday through Tuesday.
&&
.UPDATE...
Issued at 1007 AM EST Wed Dec 11 2024
The first wave of snow has exited the region to the east, leaving a
path of Trace - 0.5 inches of snow on the ground. Morning commute
had little to no impact with mostly damp roads.
Temperatures are currently sitting in the upper 20s and low 30s.
Under clearing skies and CAA, temperatures are expected to warm up,
however, we are not expected to rise much out of the 30s this
afternoon.
As the deep troughing aloft and CVA swings through the region today,
another wave of snow showers is expected to push through the region.
Best timing on this is 19Z through 01Z. Model soundings show 35-50
J/kg of SBCAPE, 25-35kts of 0-3km shear, low LCLs, steep lapse
rates, marginal surface temperatures near freezing, and plenty of
moisture within the DGZ. These conditions bring the snow squall
parameter to about 3-4. Best chance for heavy snow showers or
squalls will be over the Bluegrass and northern Kentucky/southern
Indiana. Given the scattered, cellular nature of these showers and
squalls, moderate translation speed of showers, and the low snow
accumulation, have decided to continue the current SPS. If snow
squalls develop, brief reductions in visibilities and accumulation
on roads is possible.
With sunset, temperatures are expected to drop below freezing. Slick
spots may develop on roads where there has been recent snowfall.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 318 AM EST Wed Dec 11 2024
Current radar mosaic shows a narrow band of precipitation stretching
from Richmond, IN SSW towards Hopkinsville, KY to Greenville MS.
This band of precipitation was a result of mid-level frontogenesis
around 700mb. Per observations, most of this activity was not
reaching the ground, but snow had been observed over Hopkins and
Muhlenberg counties in KY. This is the first of two waves of
precipitation that will work across the area today. As this first
band of snow continues to push eastward this morning, models
continue to show this band of snow intensifying around I-65 with a
brief period of snow from Bowling Green to Louisville around 5am to
7am EST, then continuing towards Lexington and the I-75 corridor
between 7am to 9am EST. With temperatures currently near or above
freezing, and road temperatures expected to stay just above freezing
this morning, impacts from the snow should remain minimal but
bridges and overpasses where temperatures have dropped below
freezing this morning could turn slick as well as low visibility in
heavier bursts of snow. Most of this activity will push east and out
of the area by mid to late morning with even some sunshine coming
out from late morning towards midday. This will help to warm up
temperatures into the upper 30s to even low 40s towards the early
afternoon.
Deep upper level trough and associated vort max will start to push
through the Ohio Valley this afternoon and into the early evening.
Colder air will continue to advect in from the west-northwest with
850mb temperatures falling to around -8C by the time this
disturbance works across the area. Low level lapse rates will
steepen to between 6-8 C/km this afternoon, with model soundings
showing 50 J/kg SBCAPE. This along with the lift from the
approaching vort max will help in developing cellular convective
snow showers this afternoon and evening. Current thinking is the
best time for development is from about 21z to 00z, just in time for
the late afternoon and early evening commute. The other thing to
note is models show snow squall parameters between 2-4, with the
highest values into the Bluegrass and along the I-75 corridor.
Isolated snow squalls are possible within the scattered convection
later this afternoon and early evening. The main limiting factor
continues to be air and sfc temperatures into the upper 30s to even
low 40s this afternoon. Temperatures are expected to fall after
sunset but should remain just above freezing during the window of
best opportunity. While temperatures remain the limiting factor in
all of this, like we saw last year on Dec. 18th with a similar
setup, snowfall rates can overcome melting and cause roads to be
slick and hazardous very quickly. Winds will also be gusting to
around 20 to 25 mph this afternoon and could be strong with an
associated snow squall causing very low visibility. For now, we will
continue with an SPS for the scattered snow showers and possible
snow squalls this afternoon and evening, but as was mentioned in the
previous discussion, a brief winter weather advisory could be issued
if needed later today for the evening commute.
As for overall snowfall, amounts look to be around a coating to
below a half inch. Most snow will accumulate on grassy and elevated
surfaces. The exception would be from more intense and heavy
snowfall from potential snow squalls.
Overnight, trough axis pushes off to the east and the snow shower
activity comes to an end. Skies are expected to clear with the
coldest 850mb temperatures (-10 to -12) over southern IN and central
KY. Lows will be cold falling into the low 20s to upper teens. While
winds are expected to diminish overnight, there will be enough of a
breeze to keep wind chill values in the low/mid teens.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 318 AM EST Wed Dec 11 2024
The Long Term period will start with dry conditions Thursday through
Friday night. Cool temperatures will remain in place Thursday
despite the region being located south of a warm front reaching from
low pressure over northeast New Mexico eastward to the Ohio Valley.
Mostly sunny skies will work on any slick spots on area roads
Thursday morning, and afternoon temperatures will peak from the
middle 30s in southern Indiana to the lower 40s in southern
Kentucky. Then on Friday a sprawling dome of strong high pressure
over the Northeast will provide us with return flow, pushing the
Ohio Valley warm front northward and enveloping the area in warmer
air. High temperatures Friday are expected to vary from the upper
40s in southern Indiana to the mid 50s in southern Kentucky.
On Saturday low pressure crossing the Midwest will pull a cold front
eastward to the Mississippi River by evening. This system will have
full access to the Gulf, with moderate IVT from the Texas coast to
the Great Lakes behind a healthy surface ridge along the
Appalachians. As a result, confidence is high in widespread showers
Saturday and Saturday night, with categorical PoPs in the forecast.
Thunder looks unlikely given cool temperatures, showers, overcast
skies, and weak forcing aloft. Scattered showers will continue into
Sunday but the rain will be lighter and less widespread as the
system continues to weaken. Still, we're looking at a wet weekend.
Total rainfall amounts for the weekend are progged to be around an
inch. High temperatures both days will be in the 50s, with lows
Saturday night in the 40s with a steady 5-15mph south wind, so no
snow.
Progressive pattern will then bring the next system into the region
as we start the new work week, with more shower chances in the
forecast for Monday and Tuesday. Once again thunder looks unlikely,
and snow chances are small given temperatures expected to stay above
freezing. Highs Monday and Tuesday will mostly be in the 50s, with
lows Monday night 35-40.
&&
.AVIATION /18Z TAFS THROUGH 00Z FRIDAY/...
Issued at 1258 PM EST Wed Dec 11 2024
Mostly VFR across the area currently with some clouds lingering over
the Bluegrass at high-end MVFR. Within the next few hours, scattered
snow showers will begin to develop and move through the region. Some
showers may become heavy bringing a reduction in visibilities and
gusty winds. Best chance for these conditions will be over
SDF/LEX/RGA/HNB from 20-02Z. Once these showers exit the region to
the east, skies will quickly clear, restoring VFR conditions through
the remainder of the TAF period. Winds will steadily relax through
the overnight, as pressure gradients broaden.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.
&&
$$
UPDATE...SRM
SHORT TERM...BTN
LONG TERM...13
AVIATION...SRM
Source:
LMK issues Area Forecast Discussion (AFD) at Dec 11, 12:59 PM EST ...Updated Aviation Discussion...---------------
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