textproduct: Louisville

KEY MESSAGES

* Patchy Dense Fog expected to develop across portions of SW Indiana and central and southern KY tonight.

* Weak frontal boundary slides south through the area this evening, leading to a wide temperature range north to south across our area tonight. Upper 30s to low 40s north of I-64, to upper 50s near the KY/TN border.

* Unseasonably warm temperatures are likely around Christmas, with temperatures expected to be 15-20 degrees above normal. Record warm min temps possible Friday morning.

* Mild weather continues into the first part of the weekend, but will gradually trend cooler by Sunday with a series of reinforcing cold fronts. More substantial rainfall amounts, and potentially a few thunderstorms, are possible with the weekend cold front.

UPDATE

Issued at 934 PM EST Tue Dec 23 2025

Quiet conditions ongoing across the area with mild temperatures and some lingering drizzle across central and southern KY. Expecting fog to develop as we go through the overnight, mainly along and south of a line from Jasper, IN down through Stanford, KY. Guidance suggests this, and we are starting to see good evidence of the stratus deck lowering on KY Mesonet webcams across Ohio, Butler, Logan, and Grayson counties. Have gone ahead and issued a Special Weather Statement mentioning dense fog wording overnight, and put areas of dense fog in the grids along and south of that aforementioned line. Expecting we may need a Dense Fog Advisory at some point tonight, but want to see evidence of that stratus build down on webcams/obs before we commit to a headline.

SHORT TERM /THROUGH THIS AFTERNOON/

Issued at 300 PM EST Tue Dec 23 2025

Even though we have have been overcast today, low level warm air advection has helped our sfc temperatures warm into the mid to upper 60s. Regional radar mosaic shows some patches of very light rain or even drizzle across central KY, but little to no liquid accumulation is expected.

For tonight, building high pressure over the Great Lakes will continue to push the weak sfc boundary south toward the KY/TN border, keeping at least a low-end chance for light rain or drizzle in the forecast across south-central KY through the overnight. Temps for tonight could end up being quite tricky, as they will be dependent on where the front will be. Some partial clearing of clouds north of I-64 could help drop temps even more, and we could end up seeing a 18-20 degree temperature gradient north to south across the forecast area by tomorrow morning. Lows will range from upper 30s and low 40s for southern IN and north-cenral KY, to upper 50s near the KY/TN border. Low stratus will be accompanying the sfc boundary tonight, but could see some instances of patchy fog overnight too.

For tomorrow, the weak sfc boundary will begin to lift back to the north as a shortwave approaches the region. Model soundings suggest drier air in place tomorrow, so less chances for light precip and drizzle. However, temps still look to vary north to south across our area, with highs ranging from upper 50s in our north, to upper 60s in our south.

LONG TERM /TONIGHT THROUGH TUESDAY/

Issued at 300 PM EST Tue Dec 23 2025

===== Christmas Day through Friday Night =====

We remain under a progressive NW flow upper level pattern, with a sfc boundary meandering across the Ohio Valley for Christmas and Friday. Light rain activity remains possible for Christmas morning, as we'll see a surge in low-level jetting Wednesday night that will bring an increase in low level moisture transport. With the front situated across the area, portions of southern IN and the Bluegrass will be the focus for additional light rain. PoPs remain rather high despite the low QPF, and certainly not expecting a washout. Model soundings support drizzle through the day as well, which seems reasonable given the low level moisture and deeper cloud depths in the vicinity of the boundary. We could be looking at a Top 10 warmest Christmas on record, with forecast highs in the upper 60s to low 70s for majority of the area.

The upper flow regime flattens out for Friday, but another weak shortwave looks to slide just north of the area. We'll end up more in the warm sector on Friday, as the sfc boundary should be sitting a bit more north and east during the day. WAA pattern will support even warmer temps on Friday, with highs possibly reaching closer to 70. Morning lows could very well end up breaking warm min records as well. A few rain showers will also remain possible in the vicinity of the boundary, but the best chances remain the farther north and east you go. Drier weather appears to be in store for Friday night.

===== Saturday into Early Next Week =====

We begin the weekend with dry conditions, with upper level ridging overhead, and perhaps the warmest day of the forecast period. High temps for Saturday range from the mid-60s to low-70s. We'll be near our record max temps on Saturday, but not currently expecting us to break any.

Focus then turns to our west, where an upper trough will be ejecting across the Mountain West over the weekend, initially amplifying the ridge for Saturday, but then expected to phase with a northern stream upper trough. Guidance still shows some spread on timing of phasing, though still thinking of a more delayed phase that leads to a less amplified round of precip passing through the region on Sunday with the cold front. Despite the low confidence in thunderstorm activity on Sunday, the NSSL machine-learning Severe Probabilities are showing at least a small chance for Sunday, so its worth keeping an eye on through the week.

Regardless, Sunday serves as one of the best chances for measurable precip in the period. Behind the front, strong cold air advection will quickly follow as Canadian high pressure slides into the Midwest. Temperatures will drop considerably by Monday morning, with lows down into the upper teens to low 20s. We could see a 40 degree temperature drop from Sunday highs to Monday morning lows. Drier weather is expected for Monday and Tuesday, though with temps possibly remaining below freezing.

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 1234 AM EST Wed Dec 24 2025

Impactful, but low confidence forecast ahead as low-level moisture over the region is producing both widespread IFR/MVFR stratus as well as patchy LIFR fog. A backdoor cold front is pushing into the region from the north at this hour, with stratus starting to clear across northern KY and south central IN. It is expected that this clearing trend should continue toward SDF/LEX/HNB over the next several hours, but confidence is lower that we will completely scatter out. There is higher confidence in stratus remaining over BWG through the current forecast period, though settling moisture around sunrise may end up as a combination of LIFR CIGs and IFR fog down there. For the northern TAF sites, patchy fog may try to develop if skies clear just before sunrise, and short-fuse amendments may be needed.

Later today, we expect improving categories, likely VFR conditions at SDF/LEX/RGA while HNB and BWG have greater chances of remaining under low clouds. Winds during the day are expected to veer from northerly to easterly to south-southeasterly by this evening, though speeds should remain less than 10 kt. Tonight, the backdoor cold front is expected to lift north as a warm front, with winds veering to the SW and more widespread low CIGs expected.

LMK WATCHES/WARNINGS/ADVISORIES

KY...None. IN...None.