802
FXUS63 KLMK 052335
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
635 PM EST Wed Feb 5 2025

...Updated Aviation Discussion...

.KEY MESSAGES...

*  Showers and thunderstorms will continue to spread across the area
   this afternoon and evening.

*  There is a Marginal Risk (level 1 of 5) for severe storms for
   tonight. There is a conditional threat for damaging winds, hail,
   and tornadoes. Severe storms are most likely across south-central
   Kentucky. Additional rainfall could result in some minor flooding
   issues as well.

*  Another chance of rain, and possibly storms, this weekend.

*  Wintry precipitation possible early next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 355 PM EST Wed Feb 5 2025

Temperatures across the area vary drastically depending on where you
are, with the Kentucky Mesonet showing temps ranging from the upper
30s across north-central Kentucky, to mid-50s across south-central
Kentucky. Synoptic and mesoscale analysis this afternoon reveals
that upper jet flow is mostly zonal, with an embedded shortwave
crossing the central US. At the sfc, a frontal boundary is located
across the Tennessee Valley, lifting northward as a warm front.
Scattered showers have blossomed over a portion of the forecast
area, mainly west of I-65, in response to a 30-35kt LLJ over the
Wabash River Valley and isentropic lift. As the warm front
approaches from the south, expect increasing isentropic lift to
expand precip coverage across the entire area. Sfc winds out of the
east have continued to influence low level CAA regime, but aloft the
850mb layer has a very strong warm nose due to southwesterly flow.
This cap will hold this afternoon and evening, keeping us stable at
the sfc with any instability held aloft. For late this afternoon and
evening, showers and embedded thunderstorms are likely, though
severe potential is low. Based on model soundings, the low level
inversion should hold through at least midnight.

By 06z tonight, the warm front will be pushing northward across our
area, which will veer our sfc winds to a south-southwest flow. This
will effectively erode the low level inversion as a WAA regime takes
over. Temperatures will warm through the night as WAA takes over.
With increasing synoptic scale forcing from the approaching exit
region of the upper level jet, WAA regime will help steepen lapse
rates and increase instability. Hi-res guidance suggests a plume of
SBCAPE upwards of 500-750 J/kg will spread across south-central
Kentucky, increasing the threat for severe thunderstorms in a highly
sheared environment. With strong low level helicity, a
supercell/tornado risk is still on the table, especially for south-
central Kentucky. Hi-res hodographs support supercells, and possibly
splitting supercells, given the shear in place. HRRR Neural Network
Convective Hazard Forecast highlights 09-13z as the time frame for
highest probability of severe hazards within 40km. Machine learning
guidance also places a hot spot across south-central Kentucky, with
damaging wind and hail also possible with any severe storm. The
greatest potential for sfc-based convection will be along and south
of the western KY/Bluegrass Parkways, with greater uncertainty to
the north.

There remains some uncertainty with tonight`s severe storm
potential. Per SPC, the tornado risk is conditional and largely
depends on the ability for a sfc based storm to occur near the warm
front. If convection does remain elevated, severe impacts are
unlikely to be realized at the sfc. After chatting with SPC, the
Marginal Risk will stand for now given concerns about the amount of
CAPE overnight. If confidence grows, SPC could consider a Slight
risk somewhere in our south.

In addition to the severe potential, will need to keep an eye on any
hydro issues for the overnight. The 12z HREF 24-hr LPMM does show a
swath of 0.75-1.50" across south-central KY, with a very isolated
area of closer to 2" somewhere near the Lake Cumberland area
possible. While flash flooding is not expected, some minor flooding
issues will be possible with any heavier rain rates.

For tomorrow, showers and storms will be tapering off as a cold
front gradually sweeps through the area.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 355 PM EST Wed Feb 5 2025

Thursday Night - Sunday...

A trailing cold front will be sliding through our SE CWA the first
part of Thursday night, and will have rain chances ending from NW to
SE as this occurs. Should be dry after Midnight as surface high
pressure builds in behind the front. Temps drop off pretty
dramatically behind the front, with lows back in the 30s for most
areas by dawn on Friday. This is around 30 degrees cooler from
Thursday afternoon highs. Friday looks dry with the front stalled
just to our south. This will also result in cooler temperatures on
the north side of the boundary. Will likely have a decent gradient N
to S across the CWA with mid 40s north to mid 50s south for highs.

More shower chances arrive Friday night, followed by shower and
storm chances on Saturday and Saturday night. We`ll see lee
cyclogenesis over the central High Plains on Friday, and this
feature will steadily move eastward through our area by Saturday
evening. Ahead of the surface low, increasing southerly flow will
help to lift the stalled frontal boundary to our south back north as
a warm front. So, expect some isentropic lift induced showers Friday
night. By Saturday, we look to get into the warm sector across much
of our area with the surface passing somewhere near or over our CWA
by Saturday evening. This should be another mild day with highs in
the 60s for most. Some low 70s are certainly possible across
southern KY. There is some concern that a few thunderstorms could
develop, and could bring a localized severe threat given the shear
parameters, and the classic triple point conceptual model.
Instability will be the big question mark, and if we are able to
realize some, then expect we might end up with an outlook for later
Saturday afternoon/evening. Something to watch.

Shower and storm chances diminish Saturday night as the surface low
passes and trailing cold front passes through. Cold air returns for
Sunday in our continued roller-coaster likely temp pattern, although
the cold air looks to become more established as we head into the
new work week. Sunday highs are only expected back in the 40s, with
a dry forecast otherwise.

Sunday Night - Wednesday...

Some uncertainty as we go into early and middle of next week.
Although confidence is higher that some sort of storm system is
likely to impact our region. At this point, it seems that a surface
low could steadily develop to our SE, with quite a bit of Gulf
moisture to tap into. We`ll have some cold air in place, especially
across our northern CWA where the best chance of some mixed wintry
precipitation will be. There is still uncertainty on
timing/placement/strength of individual features, but the signal is
there for some potential wintry precipitation. Farther south, rain
will be the bigger concern, especially with our continue wet pattern
and little time to recover from previous rainfall. Minor river
flooding could again come into play as we go through next week,
particularly the Green River basin. Stay tuned.

&&

.AVIATION /00Z TAFS THROUGH 06Z FRIDAY/...
Issued at 634 PM EST Wed Feb 5 2025

Poor flying conditions can be expected for the bulk of the TAF
period, especially overnight tonight. A warm front lifting north
across the region will veer winds from east to south to southwest,
while bringing low clouds, widespread showers, and scattered
thunderstorms. A strong low level jet from Oklahoma to Ohio will add
LLWS to the mix overnight. The most likely time for thunder will be
in association with this jet and a 500mb speed max while we`re in
the warm sector of the storm system during the pre-dawn hours.
Temporary low visibilities in heavy downpours will be the main
aviation threat at the surface, in addition to the usual wind
threats that come with any thunderstorm. The strongest storms could
produce brief hail.

A cold front will sweep the rain away tomorrow morning, though
moisture will remain trapped below a low level inversion leading to
persistent low ceilings. Some guidance shows these ceilings
scattering out by midday, but went more pessimistic than that in the
TAFs for now.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...None.
IN...None.

&&

$$

SHORT TERM...CJP
LONG TERM...BJS
AVIATION...13