textproduct: Louisville

KEY MESSAGES

* Areas of dense fog continue this morning across portions of the area. Fog should begin to dissipate by mid-morning.

* Intermittent chances for rain continue over the next few days, with total rainfall amounts expected to be light.

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

* A strong cold front is expected to move through the region Sunday into Sunday night. Widespread rainfall, including some thunderstorms, will be possible as the cold front passes. Temperatures plummet into the 20s by Monday morning.

SHORT TERM /THROUGH TONIGHT/

Issued at 407 AM EST Wed Dec 24 2025

High pressure passing across the Great Lakes this morning has allowed a backdoor cold front to sink into the area, with a strong north-south gradient in temperatures observed at this time. Drier air above the boundary layer has seeped into southern IN and northern KY, allowing low stratus to scour out. However, elevated dewpoints has caused many of the areas which have cleared out to develop areas of fog, with particularly dense fog noted in obs over southern IN and western KY. While an SPS has been out for several hours now highlighting the dense fog, we'll issue a dense fog advisory for areas mainly north of I-64 where clouds have cleared, though a southward expansion may be needed in a few hours.

Aside from the fog, deeper moisture continues over southern KY this morning, with isolated light rain showers and sprinkles expected to push toward the TN border over the next few hours as the cold front sags south. Later this morning, as the sfc front becomes quasi- stationary over the area, we should start to see showers diminish across southern KY and peeks of sunshine along and north of I-64 as drier air attempts to work to the south. However, by this afternoon, as the sfc high to our north departs to the east, the sfc front will begin to lift back to the north, increasing clouds across the entire area. Temperatures today should be quite variable from NE to SW, with highs expected to approach 70 along the KY/TN border, while areas north of I-64 and east of I-65 may struggle to reach 60. Winds should be fairly light through the day, veering from northeasterly to south-southeasterly as the day progresses.

This afternoon into tonight, an upper-level shortwave is expected to drop from NW to SE along the northeast fringe of the upper-level ridge. The front over the area should surge to the northeast as a warm front, with scattered showers developing along the front in a isentropic lift/warm advection pattern. As the upper trough passes to the northeast of the region late tonight, coverage of showers is expected to increase, especially across the northeastern third of the CWA (roughly Salem, IN to Richmond, KY). Model soundings do show a bit of elevated instability across northeastern KY and southeast IN, so wouldn't be totally surprised if a couple showers have rumbles of thunder later tonight. Total rain amounts will be modest as deep moisture is lacking, with most areas expected to receive less than a tenth of an inch of rain.

Temperatures will also remain fairly steady overnight tonight, or may even rise a few degrees given low cloud cover and increasing mild SW flow. Expecting temperatures to remain in the low 60s across southern KY, with temperatures rising into the upper 50s and low 60s across northern KY and southern IN.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 407 AM EST Wed Dec 24 2025

Christmas Day through Saturday Night...

A fairly consistent synoptic pattern is expected for Christmas Day through the end of this week. Broad upper level ridging across the south central US will keep an unseasonably warm air mass in place from the Ohio Valley and points to the south and west. Our area will be on the northeastern edge of the upper ridge, providing a baroclinic zone/storm track which shortwave disturbances will track along during the late week period.

The first of these disturbances should be clearing into the central Appalachians Christmas morning, dragging a quasi-stationary sfc front back into the northeastern portion of the forecast area. While the deeper moisture and stronger forcing will be exiting during the morning hours on Thursday, ample low-level moisture will likely keep low clouds, drizzle, and scattered light rain showers going through much of Christmas Day, particularly across the KY Bluegrass. By no means will this be a washout, as total rainfall amounts are only expected to be between a few hundredths and a tenth of an inch. Temperatures will be mild across the area, with highs close to 70 along and west of the Natcher Parkway, while highs should be closer to 60 across the KY Bluegrass and much of southern IN.

Christmas night into Friday morning, another upper shortwave is expected to pass north and northeast of the area, bringing a sfc low through the lower Midwest. Ahead of the sfc low, warm return flow will keep temperatures fairly stagnant or slowly rising into Friday morning, with some light precipitation possible along a NE-lifting warm front. Again, most of the rain with this system is expected to fall to the northeast of our area, with only trace amounts to a tenth of an inch expected across the LMK CWA. With the warm front more likely to be northeast of the area during the day on Friday, temperatures should take a step up, with highs expected to range from the mid 60s to the low 70s. This will get us in the vicinity of record highs at BWG, with other climate sites comfortably below records at this time.

Friday night, clearing is expected across the area as the upper ridge flexes back to the north and east. The lowest chances for rain through this weekend are expected on Saturday, with mild temperatures continuing as highs should range from the mid 60s to the low 70s. Again, BWG will flirt with a record high Saturday, with other sites expected to be below record highs. Another surge of warm return flow is expected Saturday night as our next system begins to take shape over the mid-Mississippi Valley and the upper Midwest.

Sunday through Early Next Week...

The trough in the subtropical jet stream which will hang out off the California coast for much of the rest of the week will begin to eject eastward on Saturday. At the same time, a polar stream trough moving across Canada will attempt to phase with some of the energy from the subtropical jet, with models coming into greater agreement on a deepening system over the upper Midwest Saturday night into Sunday. As the upper trough deepens, surface response should promote a strengthening sfc cold front just north of the Ohio Valley on Sunday. The last few runs of medium-range guidance have trended slower with FROPA, which now looks more likely Sunday afternoon into early Monday morning.

Ahead of the cold front, there will be decent low-level moisture advection, with PWATs and surface dewpoints rising in the immediate pre-frontal environment. Most medium-range progs show a plume of low 60s dewpoints, which will be marginally sufficient for convective development along the front. Shear will be strong given the amplified upper flow pattern, so this looks like another potential high-shear, low-CAPE setup with marginal instability. Still, models vary in exactly how robust the moisture return will be, but forecast soundings suggest that we'll need to watch this system over the coming days. Outside of the strong storm potential, the deeper moisture and stronger mid- and upper-level forcing will support more substantial area-wide rain totals Sunday into Sunday night, with ensemble mean QPF now approaching 0.50" with this system. Temperatures will drop sharply behind the cold front, but it still looks like most if not all the precipitation should fall as rain.

Temperatures will return to below normal levels and may drop as much as 40-45 degrees Sunday night into Monday as strong cold advection overspreads the region. The synoptic pattern favors continued cold and dry weather through the first part of next week as North Atlantic blocking should keep cold air flowing into the eastern US. The current forecast calls for highs in the 20s and low 30s on Monday and Tuesday, with lows in the teens Monday and Tuesday night.

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 645 AM EST Wed Dec 24 2025

Visibilities should reach their lowest point over the next 1-2 hours, and are expected to improve across the area between 13-15Z. From about 15Z onwards, would expect CIGs to return to being the primary driver of flight categories, with SDF/LEX/RGA having the best chances to return to VFR conditions as low moisture scatters out later this morning. Winds today are expected to continuously veer from NE to SE, before becoming S/SW tonight and increasing to around 10 kt. This is due to a warm front lifting back to the north later today, with lower CIGs returning later this evening and tonight along the front.

Scattered showers are expected to develop this afternoon and evening, with the greatest coverage of showers expected to be over LEX and RGA tonight. Can't completely rule out TEMPO VIS drops with these showers, but confidence is too low at this time. It is more likely that as moisture settles Thursday morning, VIS will drop as areas of mist develop. CIGs will also drop again tonight into Thursday morning, with low MVFR/IFR CIGs possible.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for KYZ023>035-038-039-045>047-053>055-061>065. IN...Dense Fog Advisory until 9 AM EST /8 AM CST/ this morning for INZ076>079-083-084-089>092.