NWS Jackson, KY wrote its last area forecast discussion before the first event at Jan 5, 7:19 AM EST, 41 minutes earlier. Its key messages:
Area forecast discussion, Jan 5, 7:19 AM EST, 41 minutes before
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
719 AM EST Sun Jan 5 2025
.KEY MESSAGES...
- A major winter storm system will impact the area today and
Monday, bringing a mix of wintry precipitation types.
- Arctic cold will sweep across the region behind the early week
system, with apparent temperatures (wind chills) falling to near
or below zero in many places by Thursday morning.
- A weaker system may bring light snow accumulations Friday into
Saturday.
&&
.UPDATE...
Issued at 719 AM EST SUN JAN 5 2025
Freshened up the hourly temperatures, dewpoints, relative
humidity, and winds grids using obs from the past several hours.
After warming several degrees over the previous few hours,
temperatures at the 12Z ob actually fell a degree at many
locations around eastern Kentucky. After looking ahead at
temperatures trends for the rest of today, decided not make any
major changes. After recalculating today's high temperatures based
on current trends, forecast highs changed by roughly a degree on
average across the forecast area, which did not warrant the
issuance of a new zone forecast. The forecast is now on track
again using the latest obs. The updated grids were saved,
published, and sent to NDFD and remote web servers.
UPDATE Issued at 635 AM EST SUN JAN 5 2025
Had to do a quick grid update to raise temperatures across the
area. Temperatures since 8Z have not been cooling nearly as much
as previously forecast due to the insulating effect of incoming
low and middle level cloud cover. Had to increase temperature as
much as 5 to 9 degrees warmer than original forecast values to
account for the effects of cloud cover. Based on trends in
forecast hourly temperatures for the rest of today, it appears
that the forecast highs for today are still on track. Shouldn't
see any big increases in temperatures the rest of today as clouds
continue to stream in and precipitation finally begins a early
this morning. No need to issue new zones at this time. The edited
grids were saved, published, and sent to NDFD and the remote web
server.
&&
.SHORT TERM...(Today through Monday)
Issued at 405 AM EST SUN JAN 5 2025
The singular focus of the short term portion of the forecast will be
the winter storm that will be affecting the region today, tonight,
and tomorrow. The overall model solutions, NAM12, NAMNEST, and HRRR,
all were in pretty good agreement with the track and evolution of
the storm as it develops and moves eastward out of the south central
Plains and then across the mid-Mississippi and Tennessee Valleys. The
first wintry precipitation should begin moving into the I-75
corridor around 12Z this morning, and will steadily spread northward
across the area throughout the day. The first rounds of precipitation
should be a mix of snow, sleet and freezing rain. The precipitation
should quickly change over to mostly snow by late morning, with
heavy snow occurring across a large part of the area through mid-
afternoon today. As the day progresses, and the warm nose aloft
moves further and further north, we should see a messy mix of sleet
and freezing across all of the area by late this afternoon, with
freezing rain being the predominant precipitation type. The freezing
rain will push northward into tonight, but will be displaced from the
south by all rain, as warmer air spills into the area near the
parent low pressure area. After several hours of rain generally
south of the I-64 corridor tonight, a second shot of colder air will
push into the area from the northwest, as the low pressure system
moves off to our east. This will lead to another transition from
rain, to rain/snow, and eventually a freezing rain/snow mix. The
precipitation should change over to all snow again Monday afternoon,
with additional light accumulations expected.
Another issue with this storm will be the wind. Winds could gust to
over 20 mph at times on Monday, which could lead to damage to trees
and powerlines due to excess snow and ice accumulations. Power
outages will be a definite possibility on Monday. Travel will become
difficult to nearly impossible in the areas of eastern Kentucky that
see the highest snow and ice accumulations today and tonight. The
highest snow and ice accumulations should occur mainly along and
north of the Mountain Parkway, with the I-64 corridor potentially
being hit the hardest. After starting off in the upper teens and
lower 20s this morning, temperatures will warm up early on, and then
should remain nearly steady in the upper 20s and lower 30s for the
rest of the day.
.LONG TERM...(Monday night through Saturday)
Issued at 400 AM EST SUN JAN 5 2025
The last meaningful precipitation from the major winter storm
dominating the short term period will be winding down as the long
term period starts. We will be on the western edge of deep
moisture wrapped around the back side of the system beneath its
departing, opening upper low. We will also be in the midst of
brisk, upslope, low level cold air advection from the north
northwest. Considering both factors, the latest forecast is
generous with the probability for light snow Monday evening,
especially in southeast KY. After the deep moisture departs Monday
night, low level upslope cold air advection persists and flurries
will linger at times, possibly into Wednesday in southeast KY.
Temperatures will be very cold behind the departing winter storm.
The coldest readings look to be late Wednesday night/Thursday
morning as surface high pressure settles over the area. Clouds
should be decreasing by then, allowing for decent radiating. Have
tentatively gone with readings as cold as zero in our northern
valleys. If too many low clouds hold on, that may not be
achievable. However, if skies clear with snow on the ground, it
could be colder.
The surface high weakens and departs to the east Thursday night,
and our eyes turn to the next weather system. A large but
progressive upper level wave will drop southeast from Canada at
the end of the week, while at the same time a surface low tracks
east along the Gulf Coast, helping to send moisture northward.
Both the GFS and ECMWF have an area of light precip developing and
moving eastward over the area, and they have been persistent in
this solution. That being the case, have gone close to the likely
MOS POPs coming from both models on Friday into Friday night. It
looks cold enough to be mostly snow, but won't rule out some light
rain, mainly in southern counties. Deep moisture underneath the
upper trough lingers into Saturday, but should be departing to the
east with any lingering snow tapering off.
&&
.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 635 AM EST SUN JAN 5 2025
VFR conditions prevailing to begin the TAF period this morning.
However, conditions at the TAF sites will deteriorate rapidly
throughout the day, as a messy mix of rain, snow, and sleet move
through the area. The wintry mix will lead to a number of hazards,
including the potential for aircraft icing and very low
visibility. SME and LOZ will see their first precipitation by 14Z
this morning, JKL by 16Z, SJS by 17Z, and SYM by 16Z. Cloud cover
will steadily lower today, as a powerful storm approaches. We
should see MVFR CIGS and IFR to LIFR VSBYs at the TAF sites due to
wintry precipitation moving through the area today and tonight.
Winds will be light and variable to start the day, but should
increase to between 5 and 8kts and be out of the east by this
afternoon. The winds should shift to the south and eventually
southwest tonight.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 7 AM EST Tuesday for KYZ044-050>052-
058>060-068-069-104-106>112-114-119-120.
Winter Weather Advisory until 7 AM EST Tuesday for KYZ079-080-
083>088-113-115>118.
&&
UPDATE...AR
SHORT TERM...AR
LONG TERM...HAL
AVIATION...AR