914
FXUS63 KLMK 050838
AFDLMK

Area Forecast Discussion
National Weather Service Louisville KY
338 AM EST Wed Feb 5 2025

.KEY MESSAGES...

*  Cooler temperatures continue today, with scattered showers
   increasing in coverage this afternoon and evening.

*  Showers and thunderstorms are likely late this afternoon into
   Thursday morning. There is a Marginal Risk (level 1 of 5) for
   severe storms for this evening into tonight. Additional rainfall
   could result in some minor flooding issues as well. Confidence
   remains low for severe storms.

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

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 338 AM EST Wed Feb 5 2025

Early this morning, clouds have overspread the area as W/SW 925-850
mb flow is lifting up and over the near-sfc cool air mass and
condensing. At the surface, the cold front which pushed through the
area on Tuesday has now washed out over the Tennessee valley, where
it is expected to remain through the morning hours. For the rest of
the morning, light radar returns will likely stream across the area
from west to east, though much of this won`t reach the surface,
especially east of I-65.

Today, the area of sfc high pressure behind yesterday`s front will
pivot across the Great Lakes and into the northeast U.S. by this
evening. Our region should be right on the southern edge of the near-
sfc E/NE flow which is helping to reinforce the cool air mass.
Across south central KY, there is the greatest uncertainty in
temperatures today, with 10-15 degrees of spread in temperatures
among the 00Z HREF members this afternoon. Once the low-level E/NE
flow subsides, temperatures would be expected to quickly warm from
the mid 40s into the mid-to-upper 50s. How quickly this occurs is a
source of considerable disagreement in model guidance and will have
an impact on strong/severe storm potential this evening and tonight.

North of the Western KY and Bluegrass Parkways, there is higher
confidence that the cool near-sfc layer will hold on through the day
today, with cloud cover also helping to keep temperatures in the
mid-to-upper 30s and lower 40s.

Later today, an upper shortwave will eject from the Rockies into the
central Plains, continuing toward the Ohio Valley tonight. Ahead of
this wave, low-to-mid level SW flow will increase, with moist
isentropic upglide over the cool near-sfc layer supporting continued
cloud cover and increasing chances for rain showers this afternoon
and evening. Warm advection within this increasing SW flow should
allow for steepening mid-level lapse rates this afternoon and
evening, with short range guidance showing a plume of 500-1000 J/kg
MUCAPE spreading over the area. Combined with synoptic scale support
from the approaching upper jet/exit region, waves of more numerous
showers, with embedded thunderstorms, are expected late this
afternoon into tonight. As the upper wave approaches, a surface wave
will develop and move across the region late tonight into Thursday
morning. Ahead of this wave, a warm front will quickly lift across
the area tonight, with temperatures expected to warm overnight. In
the vicinity of the sfc warm front, enhanced low-level helicity and
shear would support a greater severe wind gust/spin-up tornado
potential. However, any severe impacts would be conditional on
convection becoming surface-based. The greatest potential for sfc-
based convection will be along and south of the western KY/Bluegrass
Parkways, much in line with the Day 1 SPC marginal risk. If the warm
front is faster in lifting north than currently forecasted, areas
across north central KY would have an increased risk for severe
winds and spin-up tornadoes this evening and tonight. On the other
hand, the primary failure mode for severe weather tonight would be
if convection remains elevated, with severe impacts never
translating to the ground. While the greatest potential for strong
to severe storms will be in the mid-to-late evening hours with the
warm front lifting across the area, forecast soundings suggest a
lingering (but decreasing) potential into early Thursday morning
ahead of the sfc cold front.

While large-scale precipitation amounts aren`t expected to be
particularly great with this system, 00Z HREF does show the
potential for localized swaths of 2-3", especially across south
central KY. If this is realized, localized flash flooding will be
possible across parts of the area.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 338 AM EST Wed Feb 5 2025

Unseasonably warm and rainy conditions expected on Thursday as the
cold front lays out nearly parallel to the zonal upper flow, thus
slowing to a crawl in its southward progress. Look for the focus to
be mainly in Kentucky, especially in the south to begin but waving
back to the north later as another impulse swings through the Ohio
Valley.

The window for severe potential closes rapidly around daybreak if
not before, as low-level shear weakens. Could still see an isolated
thunderstorm here or there, but will struggle to get sfc-based
convection. Anomalously high PWAT values pushing 1.25 inches, along
with the slow movement of the front, will leave the door open for
locally heavy rainfall. Basin averages will be around a half inch of
additional rainfall, mainly across south-central Kentucky, which is
low enough to mitigate the broader impacts of localized higher
amounts.

Overall unsettled pattern will continue through the weekend, with a
flat and progressive flow aloft. Disturbances in the upper flow will
trigger waves of precipitation, which are notoriously difficult to
time in this pattern. At this time, Friday looks like the best
chance at a dry day, and Sunday could also remain dry especially
across southern Indiana. The flip side is that the dry days will
correspond to the cooler temperatures, which could end up below
normal on most of the days it doesn`t rain.

Below normal temps will take hold early next week as we transition
to a broad eastern CONUS trof. Another system on Tuesday could bring
a period of wintry mix, with snow not out of the question especially
north of the WK/BG Parkways. Max temperatures will run in the 40s
through that period, with nightly mins just either side of freezing.

&&

.AVIATION /06Z TAFS THROUGH 12Z THURSDAY/...
Issued at 1235 AM EST Wed Feb 5 2025

Tricky forecast during the current TAF period with impactful
ceilings, visibilities, wind shear, and possible TS expected. So far
tonight, MVFR CIGs have stayed largely along and south of a line
from OWB to FTK to IOB, with VFR conditions observed north of this
line. These MVFR CIGs are not expected to move much until after
sunrise later this morning; however, only slight shifts would be
required to get SDF and LEX into the MVFR CIGs, so forecast
confidence in only medium. By mid-to-late morning, increasing
moisture and SW winds just off the surface should spread the MVFR
CIGs northward, with falling CIGs expected through the day at all
sites. Scattered rain showers could bring brief VIS reductions this
afternoon; however, CIGs should remain as the primary driver of
categories.

This evening into tonight, a warm front will lift north through the
area, bringing VIS and CIG reductions in its vicinity. Toward the
end of the current forecast period, isolated TS chances will
increase; however, confidence in timing and coverage is so low, will
take it out of the forecast for now. Increasing SW flow aloft will
also bring the potential for LLWS after 03Z tonight.

&&

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

&&

$$

SHORT TERM...CSG
LONG TERM...RAS
AVIATION...CSG