textproduct: Louisville

KEY MESSAGES

* Above normal temperatures expected once again today.

* Gradient wind gusts of 30-40 mph are expected today ahead of a strong cold front. Widespread rain showers are expected. Brief/isolated wind gusts of 40-45 mph will be possible in stronger showers along the front.

* Behind the front, dramatic temperature fall will be seen overnight with a few snow flurries and snow showers possible. Cold weather will last through Friday. Temperatures will then warm back up over the weekend and into next week.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 255 AM EST Thu Dec 18 2025

Early morning satellite imagery shows partially clear skies across eastern Kentucky with low stratus in areas west of I-65. Early morning temperatures were generally in the upper 40s/lower 50s along and west of the I-65 corridor. Out across the east, in the more clear skies, temperatures were in the lower 40s with the more protected valleys in the lower 30s. No significant weather is expected through sunrise. The pressure gradient will continue to increase over the next several hours, so expect southerly winds to become more breezy by sunrise.

For today, a rather active day of weather is expected across the region as a strong cold front drives eastward from the Midwest and into the Ohio Valley. Potent shortwave trough axis aloft was moving through the northern Plains this morning with an accompanying surface low in the low 980s moving through Minnesota. This upper level shortwave trough will continue to dig and take on a neutral to slightly negative tilt as it pushes into the Ohio Valley later tonight. Ahead of this upper trough and front, the pressure gradient will increase markedly through the day. Strong southerly winds will boost temperatures into the upper 50s and lower 60s.

Ahead of the approaching shortwave trough, large scale height falls, on the order of 200m, will overspread the Ohio Valley and result in strong synoptic scale lift. This will likely result in widespread rain showers developing. A low-level jet axis of 60-65kts will be overhead as well. Downward momentum transfer will likely not become maximized in this regime due to poor lapse rates, abundant cloud cover, and the presence of a low-level thermal inversion. Probabilistic ensemble guidance only shows a 20-30% chance of exceeding 40 mph gusts along/north of the I-64 corridor. In general, gradient winds of 20-25 mph with gusts of 35-40 mph will be seen across the region ahead of the front. The front will approach the region from the west late this afternoon. High resolution guidance continues to show a thin squall line developing right along the frontal interface. HREF guidance continues to show very limited amounts of instability this afternoon ahead of the front and based on the aforementioned soundings, it appears that this squall line will remain elevated as it passes through the region. It still may be possible to mix down some higher gusts right along the surface front this evening, where we could see some isolated gusts of 40-45 mph briefly. Given that the model guidance continues to trend weaker with instability and the overall intensity of showers, QPF values have also trended downward. 24h ago, it looked like we'd see 0.75-1 inch of QPF with this system, now most guidance is in general agreement with 0.6-0.75 inches.

Still think we'll see a double frontal structure with this system. Front number one will pass through during the early-mid evening with winds shifting quickly to the west in the post frontal airmass. As this front moves east, we'll see precipitation shut off from west to east. Later in the night, likely after 19/08Z or so, the secondary front with the arctic air will push through the area. Lapse rates will steepen in the wake of that front and we may be able to squeeze out some snow flurries and/or some snow showers as temps fall into the the upper 20s. There is still a small possibility that a flash freeze could occur by dawn Friday morning. However, this threat may be largely mitigated due to winds remaining gusty overnight which will dry out road surfaces. Secondly, pavement temperatures will be quite warm given the recent warmth and temperatures overnight will remain above freezing until very late. So by the time temps drop into the upper 20s, road temps will likely lag behind by several hours. Will keep a close eye on the snow shower chances late tonight as those could yield a quick coating in spots, though the highest risk of that looks to be in areas along/north of I-64.

For Friday, a rather cold/blustery day is expected with highs only warming into the lower 30s over southern IN and northern Kentucky. South of the Parkways, mid-upper 30s are expected though a few 40s are possible down along the KY/TN border. We should see clearing work into the region late in the day and into Friday night with lows dropping into the mid-upper 20s, though protected valley locations could drop into the lower 20s.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 255 AM EST Thu Dec 18 2025

For the extended period, increasingly zonal flow aloft will be seen on Saturday as high pressure moves over us early Saturday and then off to our east Saturday afternoon. Temperatures will rebound quite quickly with highs in the lower 50s across southern IN and northern KY with mid-upper 50s across southern KY. Saturday night we'll see another low pressure system move eastward across the Great Lakes and drag another front across the region. Could see some light rain showers with that which could mix with some snow showers by Sunday morning as lows drop into the upper 20s/lower 30s.

Sunday and Sunday night look to remain rather dry with highs on Sunday coming down a bit. Readings look to top out in the lower 40s across the north with mid-upper 40s across the south. Temps will tick slightly warmer on Monday with highs in the low-mid 40s in the north and upper 40s/lower 50s in the south.

The pattern for Tuesday/Wednesday will feature an upper level ridge gradually growing over the TX and the southern Plains while the Ohio Valley remains in the eastern periphery within a northwest flow regime. Storm track will remain well to our north with periodic disturbances moving through the Great Lakes and into the interior northeast US. These systems may drive some weak frontal boundaries into the region producing light rain showers and a gradient of temperature (cooler NE to warmer in the SW). Highs Tuesday will range from the upper 40s over the Bluegrass to the mid-upper 50s in the Bowling Green/SW areas. Slightly warmer temps are expected by Wednesday with highs ranging from the low-mid 50s in the NE to the lower 60s in the south/southwest sections.

AVIATION /12Z TAFS THROUGH 18Z FRIDAY/

Issued at 606 AM EST Thu Dec 18 2025

Conditions will start to go downhill in a couple of hours as cigs start to come down and rain showers develop across the region. Winds will pick up out of the south this morning with gusts of 20-25kts by mid-late morning. More widespread rain showers will be seen across the region this afternoon/evening ahead of a strong cold front. Gusty gradient winds 18-22kts with gusts to 30kts will be possible. Some higher gusts to 35kts could occur in heavier showers.

Frontal boundary will enter the region in the west by early evening and pass through the TAF sites between 18/23Z and 19/03Z. Look for winds to quickly shift to the west in the post frontal airmass. Winds will remain gusty overnight with gusts of 20-25kts possible through 19/12Z.

LMK WATCHES/WARNINGS/ADVISORIES

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