textproduct: Louisville

KEY MESSAGES

* Milder temperatures and intermittent light rain chances are expected during much of the upcoming week.

* Unseasonably warm temperatures are likely around Christmas, with temperatures expected to be 15-20 degrees above normal.

* 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.

SHORT TERM /THROUGH TONIGHT/

Issued at 331 AM EST Tue Dec 23 2025

This morning, a mild and muggy air mass is present over the region as temperatures are 20-30 degrees warmer than this time Monday morning. Widespread low clouds and southerly flow have helped to keep temperatures fairly steady overnight, and temperatures should remain steady or warm slightly between now and sunrise. Scattered light rain showers have been persistent overnight thanks to a 50 kt 850 mb jet. While the core of this jet is now pushing to the east, a secondary lower jet is nosing into the area from the SW, and should continue to support scattered showers through mid-morning.

Later this morning, the plume of greatest moisture is expected to shift southward into southern KY, with drier air attempting to work into the area from the north. This should help to decrease the coverage of scattered rain showers, especially along and north of I- 64. Still, model soundings show a 3-5 kft deep saturated layer, which could lead to patchy drizzle and mist through the day. A sfc cold front currently over the upper Midwest will sink southeast later today, causing winds to gradually veer from S/SW to W/SW this afternoon and evening. The cool advection behind the front shouldn't make it into our area today, and temperatures are expected to remain mild, with highs in the upper 50s and low-to-mid 60s.

Tonight, building high pressure over the Great Lakes will give an additional southward push to the decaying cold front. This surge should send the boundary through much of our area, with most models showing the front ending up near the KY/TN border Wednesday morning. Light northerly winds will help temperatures to fall behind the front tonight, which should result in a strong temperature gradient across the region. The current forecast for lows tonight ranges from the upper 30s across our northernmost counties to the mid-to-upper 50s along the KY/TN border, with confidence in temperatures at any location being fairly low given the strong gradient. Drier air will attempt to scour out clouds from the north late tonight. If this occurs, patchy fog would develop Wednesday morning, though confidence in this is pretty low.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 331 AM EST Tue Dec 23 2025

Christmas Eve through Friday Night...

Expansive upper level ridging will be present across the south central US from Christmas Eve through the end of the week, and southern IN and central KY should be on the northeast side of this ridge. As a result, we'll be in a NW upper flow pattern, with two shortwaves transiting within this pattern expected to bring chances for light precipitation.

Wednesday morning, the remnants of a sfc cold front will be draped across the region, resulting in a strong north-south gradient in temperatures. As the first of the two shortwaves approaches the region from the NW Wednesday afternoon, the boundary is expected to start to lift northeast as a warm front, continuing northeastward into early Christmas morning. It is likely that the strong gradient in temperatures will continue during the day on Wednesday, with the current forecast featuring highs ranging from the mid 50s across Jefferson County, IN and the northern KY Bluegrass to the mid-to- upper 60s along the KY/TN border.

Strengthening 850 mb flow should bring another surge of low-level moisture into the region Wednesday night, with the sfc boundary serving as a focus for new development of light rain showers. Wednesday night into Christmas morning should bring little drop in temperatures with temperatures likely within a few degrees of Wednesday afternoon. While PoPs are high Christmas morning, especially across the KY Bluegrass, expected precipitation amounts are light, generally 0.10" or less, so it shouldn't be a washout. Chances for rain should diminish later in the day on Christmas, but mostly cloudy skies and pockets of mist and drizzle will linger through the day. Highs Christmas Day are expected to be mild, in the mid-to-upper 60s across the area, with slightly higher uncertainty across our northernmost counties closer to the front.

A similar setup is expected on Friday as another upper shortwave slides just to the north of the region. By this point, upper level NW flow will become more zonal, which increases confidence that most if not all of the region will be in the warm sector. Widespread mid 60s to low 70s are expected for highs on Friday, which will get us close - but probably slightly below - record highs for the day. Scattered showers are expected again on Friday, with best chances the farther north and east you go, and precipitation amounts remaining light. Mild temperatures and diminishing rain chances are expected Friday night.

Saturday through Early Next Week...

A synoptic-scale trough which is expected to remain fairly static along the west coast of North America through Christmas Day will begin to eject to the east Friday night into Saturday. Initially, this will shift the upper ridge axis over our area on Saturday, resulting in the best chance for dry weather and what could be the warmest temperatures of this stretch. For this forecast update, highs on Saturday now range from the upper 60s to the mid 70s across the area, which will again challenge daily high temperature records.

Saturday night into Sunday, a northern stream upper trough over central Canada is expected to deepen and dig into the upper Midwest. Low-level response to falling heights aloft should lead to the development of a cold front across the Midwest and mid-Mississippi Valley late Saturday night. While there is still quite a bit of spread in how this system interacts with the energy ejecting out of the western US, more recent model guidance has trended toward more delayed phasing of the upper waves. As a result, moisture return and instability ahead of this system is less concerning, but remains marginally concerning for thunderstorm development Sunday. AI probabilistic severe hazard guidance does show a weak signal during this period, so we'll have to keep watching in case model guidance trends more unstable over the coming days.

Regardless, as the upper jet core moves into the Midwest on Sunday, widespread precipitation is likely to develop along and ahead of the front. Sunday should feature the best chance for more significant precipitation over the next week given that the forcing mechanisms at play will be stronger. Behind the front, strong cold advection later Sunday into Sunday night will send temperatures tumbling from well above normal to below normal. Exactly when that drop occurs is uncertain, but it is increasingly likely that below normal temperatures will return for the first half of next week. Drier weather is also favored for next Monday and Tuesday as a cP air mass settles across the region.

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 649 AM EST Tue Dec 23 2025

Fairly low confidence forecast during the current TAF period as CIGs are bouncing between VFR, MVFR, and IFR categories across the area. Generally expect CIGs to be the main driver of flight categories through most of the current forecast period, with predominantly MVFR CIGs and occasional IFR expected later today. Winds should gradually relax and veer from S/SW to W to N/NE through the current forecast period as a cold front approaches the region from the north and northwest.

Some model guidance has skies clearing after 0Z this evening, particularly at the northern TAF sites (SDF/LEX/HNB), though confidence in this solution is only medium at best. There is also the potential for patchy fog reducing VIS later tonight as winds should be fairly light and moisture settles. Overall, a low confidence forecast where frequent amendments may be needed.

LMK WATCHES/WARNINGS/ADVISORIES

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