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KEY MESSAGES

* A strong cold front will move through the region tonight. Showers and strong wind gusts of 40-45+ mph are likely. Localized severe wind gusts of 60+ mph are also possible, mainly between 7 PM this evening and 12 AM EST Monday.

* Temperatures plummet into the 20s and 30s by Monday morning, with colder weather lingering through next week. Wind chills will reach the teens and may briefly drop into the single digits Tuesday morning.

MESOSCALE

Issued at 840 PM EST Sun Dec 28 2025

Per Dubois County Emergency Management, all wind gusts associated with the convective line have been under 50 mph so far. The 01z Mesoanalysis suggests that 60kts of effective bulk shear stretches in a narrow corridor from the KY/TN state line to southern IN. Additionally, a thin swath of 300 m2/s2 of sfc-1km helicity now expands across all of KY just ahead of the line, which may linger for another hour or so before weakening. Taking a look at radar, the line appears to be a bit more conducive for front end nubs and mesovortices mainly north of the Western KY Pkwy. Still watching for little surges and line breaks as well, which could very well be enough to issue a SVR. While there are no plans at this time to expand the Tornado Watch, will be keeping a close eye on the line as it approaches the forecast area. The watch currently runs to 02z, and even though the convective line is just about through Orange and Dubois, we may extend it one more hour just to keep the option for us to do a local extension if needed.

Issued at 758 PM EST Sun Dec 28 2025

Closely watching the severe line of storms passing through the Evansville area at this time. Generally, the intensity of the line has weakened some since it developed across central IL as it runs into weaker instability. However, VAD wind profiles show the 55kt LLJ around 3-4k ft, leading to strong shear parameters. SPC Mesoanalysis indicated a pocket of 65kt effective bulk shear values where severe warnings remain along the line in PAH and IND areas. Additionally, sfc-500 helicity is rather impressive, with a zone of 300 m2/s2 just north of Evansville and extending north into central IN. While the shear is undoubtedly impressive, instability parameters are not quite as strong, with MLCAPE up to 250 J/kg mainly over KY and reaching just up to Dubois county. Damaging wind gusts along the line remain the primary hazard, but given what we have seen to our west over the last few hours, little kinks in the line have caused embedded mesovortices that quickly appear and disappear. Due to this, while we still expect the line to continue to gradually weaken as it slides east, given the amount of shear at play, there is still a risk for line surges and quick meso developments, particularly across our southern IN counties.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 305 PM EST Sun Dec 28 2025

Afternoon satellite imagery shows clouds have scoured out a bit across central and eastern Kentucky resulting in partly sunny skies. Temperatures at mid-afternoon were in the lower 70s. As of this writing, all of climate sites have broken their daily high temperature records. Other than the plentiful sunshine, gusty southwest winds have been increasing across the region. Based on the KY Mesonet, wind gusts of 30-35 mph have been common, though a few bursts to 40 mph have been recorded. For the remainder of the afternoon, no significant weather is expected, other than the gusty winds. A band of lower clouds will start to move into our western CWA in the next hour or so which will likely cap off any future temperature rises.

Moving into this evening, well advertised surface cold front is stretched out across MO and will be moving into the St. Louis Metro in the next few hours. Locally, we'll see gusty southwest winds continue from the afternoon into the evening hours. The cold front looks to enter our western CWA around 29/01Z or so and then pass through the I-65 corridor 29/03Z and then exit the LMK CWA by 29/05Z. Ahead of the front, a pool of moisture and steeper lapse rates will be found and this should generate a band of stronger convection right along the frontal interface. A plume of MLCAPE of 500-800 J/kg should develop along the front out to our west. However, this plume of instability looks to wane rather quickly as it approaches the I-65 corridor due to the loss of heating. Convection is likely to maximize in intensity out to our west this evening and then begin to weaken as it crosses the LMK CWA.

Highest risk of severe weather, mainly damaging winds and an isolated QLCS spin up tornado threat, would be in areas mainly west of the I-65 corridor. The storms along the front will be interacting with 40-50kts of flow at 850mb with a westerly 700mb of 65-70kts yielding SRH values of 250-300 m2/s2. While the shear is certainly impressive, the instability is marginal at best. However, cold season convection does not need much instability to get severe to occur. Given the shear profile, really can't rule out that QLCS tornado threat in areas west of I-65. A potential negative to the severe threat is that the we'll have a dense/cold airmass advancing right behind the frontal interface. In situations like this, I have seen that cold low-level flow undercut convection and keep it more elevated. Still with such strong low-level flow, stronger cores would be able to mixdown some of that higher momentum air aloft (similar to 12/18-19/25) as the front pushes through. In advance of the front, 35-40 mph wind gusts will be found, but within that thin band of convection gusts of 45-55 mph, maybe 60 in spots can't be ruled out. Given the strong gradient winds ahead/behind the front, a Wind Advisory will continue for the area this evening and into the overnight period.

Behind the front, we expect a rapid cool down given strong cold advection. Steepening lapse rates will allow additional mixing of higher momentum air aloft, so gusty west to west-northwest winds will continue into the overnight period while temperatures fall into the lower-mid 20s by sunrise Monday. The gusty winds combined with the cold air temperatures will lead to wind chills down in the single digits.

Monday will feature cloudy skies early in the day with gusty winds continuing through the morning hours and into the afternoon. The gradient will relax a bit by evening and some clearing is likely from west to east in the late afternoon. Highs will not exhibit much of a diurnal swing at all. Afternoon temps will range from the upper 20s over southern IN and north-central KY to the lower 30s along the KY/TN border. Dry and cold conditions are expected for Monday night with lows in the upper teens.

Northwest flow regime will continue across the region on Tuesday with below normal temperatures. Highs Tuesday will range from the upper 20s over southern IN and northern Kentucky to the lower 30s down across southern KY. Lows Tuesday night will mainly be in the lower 20s.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 305 PM EST Sun Dec 28 2025

Wednesday through Thursday Night...

Cold cyclonic flow will continue across the Ohio Valley Wednesday and into Thursday. Within that cold cyclonic flow, a series of clippers/perturbations will move through the Great Lakes and northern Ohio Valley. One clipper may edge close enough to yield some snow showers across far SE Indiana and into the Bluegrass region on New Years Day (Thursday). So for this forecast issuance, we'll carry some chance PoPs in for late Wednesday night and Thursday across the NE sections. Highs Wednesday will be in the mid- upper 30s across southern IN and northern KY with low-mid 40s across southern KY. Similar readings will be found on New Years Day with mid-upper 30s over southern IN and northern KY with low-mid 40s down across southern KY.

Friday through Sunday...

The upper pattern may relax a bit by late week as the upper trough axis to our north moves slightly east and the flow across the Plains and into the Ohio Valley becomes slightly more zonal. A split flow pattern is likely to develop out across the western CONUS during this time frame. A southern stream perturbation may spread some light precipitation back into the region late Friday and Saturday. Depending on the timing, a wintry mix could be seen on the northern side of this feature. Drier/colder conditions look to return to the region by Sunday.

Extended Forecast Discussion...

Moving into week two, high latitude blocking is expected across Alaska and up across Greenland. The flow across the CONUS will be highly amplified here with a broad ridge across the Rockies and a downstream trough axis along the eastern US Coast. This will place the Ohio Valley in a northwest flow regime with a gradient of temperature likely across the region. Colder readings will be found across the NE Ohio Valley with slightly milder air down toward the Ozarks. A quick moving front should bring a re-inforcing shot of colder air by Tuesday with maybe a few clipper systems zipping through in the NW Flow by mid-week.

The pattern becomes very interesting by mid-late next week (1/8-10) as significant blocking is expected to be in place across Canada and into AK with the PV displaced southward across southern Quebec. Trough axis along the western CONUS looks to shear out with pieces ejecting into the central/southern Plains. Experimental signal analysis from 12/19 had a stronger signal crossing in the 1/8-10 period which could bring some wintry weather to the Ohio Valley and Mid-Atlantic.

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 620 PM EST Sun Dec 28 2025

Keeping an eye on a line of severe thunderstorms moving across southern IL this evening, as they make their way eastward. We'll see this line pass through the area later on this evening and tonight, quickly bringing a round of showers and storms with reduced vis and cigs to the terminals. This is line is expected to weaken as it approaches the I-65 corridor, but still expect at least gusty showers across all terminals. Gusty winds will remain possible both before the line of precip, and after with the front plowing through. We'll see our gusty winds become more westerly by tonight, and some cig improvements by tomorrow.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Wind Advisory until 7 AM EST /6 AM CST/ Monday for KYZ023>043- 045>049-053>057-061>067-070>078-081-082. IN...Wind Advisory until 7 AM EST /6 AM CST/ Monday for INZ076>079- 083-084-089>092.