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KEY MESSAGES

* Winter Weather Advisory for counties along and north of I-64 for this afternoon and tonight as another quick-hitting clipper system brings an additional 1-2 inches of snow.

* Cold Weather Advisory for majority of the region on Sunday as a very cold airmass will move into the region. Forecast lows will be in the single digits and highs on Sunday in the teens and low 20s. Minimum wind chills may bottom out in the 10 below to 5 above zero range.

* The Cold Weather Advisory has been extended into Monday, as we will have a second morning with temperatures in the single digits, and maybe a few spots in the negatives. However, winds will be lighter, so wind chills will not be as cold as Sunday morning.

* Temperatures will slowly moderate Monday afternoon through mid next week, with above normal temperatures expected by Thursday.

* A cold front Thursday will bring widespread showers, and possibly a few storms, along with breezy southwest winds.

SHORT TERM /THROUGH MONDAY/

Issued at 343 PM EST Sat Dec 13 2025

=== Accumulating Light Snow This Evening === === Winter Weather Advisory North of I-64 ===

Another day with considerable temperature spread across the region, with KY Mesonet obs showing the northern half of KY hovering around the freezing mark, but our southeastern Lake Cumberland counties enjoying the upper 40s and even low 50s. That won't be the case for long though. Main focus for the remainder of the afternoon and evening hours will be the Winter Weather Advisory, which has remained the same without any changes since the early morning forecast package.

We are located underneath the right entrance region of the upper jet structure, with strong 700mb frontogenesis providing a good amount of forcing across central IN and OH. We have seen moderate to heavy snow bands streak west to east across those areas, with some light snow sneaking into our far northern CWA so far this afternoon. Mesoanalysis also notes some 850mb FGEN more in line with the I-64 corridor, with temps in that layer ranging from 0C to -6C where the better FGEN forcing is located. A weak SW 850mb jet is also bringing some WAA into south-central KY, which will help limit the snow amounts the further south you go. Based on a few ACARS data, a slight warm nose was picked up on a recent flight out of SDF that flew west. If we can end up with some precip far enough south, a rain-snow mix will be possible across central KY over the coming hours.

Overall, still think the Winter Weather Advisory placement along and north of I-64 is in good shape, as snow amounts were slightly decreased from today's data run. We'll generally see a slight southward nudge of the snow bands this afternoon, with west to east progression continuing across the area. Given sfc temps should already be dropping down to the teens across southern IN by this evening, our SLRs will be quite high, resulting in a more dry and fluffy snow. Snow ratios before 00z could range between 10:1 to 14:1, but after 00z ratios will be closer to 15:1 to 19:1 north of the I-64 corridor.

As for snow amounts, still looking at 1-2" in the advisory area, with an isolated 2-3" amount somewhere north of I-71, with the best chances for 2"+ for Jefferson County IN. However, snow probs have continued to decrease since the morning update. Madison, IN now has a 30% chance of exceeding 2" of snow, and less than a 5% chance of exceeding 4". With probs this low, the advisory will continue as is without any consideration for upgrading.

The clipper system will depart off to our east fairly quickly tonight, with most precip shutting off for most by midnight. May have some lingering light snow for the I-75 counties until 1-2AM, but mostly drier weather is expected after that. Have kept mention of lingering flurries going through the overnight, as model soundings indicate some shallow moisture that could be enough for some ice crystal formation.

=== Bitter Cold Temps Quickly Follow Behind Departing Snow === === Cold Weather Advisory For Entire Area Sunday and Monday ===

Cold Weather Advisory begins at 06z tonight as an arctic airmass quickly filters into the region behind the departing clipper system. Strong sfc high pressure will push very strong CAA into the region with gusty NW winds overnight, leading to our sfc temps to nose-dive into the single digits for all of southern IN and KY counties mainly north of the parkways. However, the gusty winds will make matters worse by plummeting our wind chills below zero, and as low as -11F. The colder values will be north, and may be exacerbated a bit by a fresh snow pack. This cold is no joke, so if you must head out tomorrow morning, dress warm and in layers, and minimize skin exposure.

Bitter cold temps continue throughout the day tomorrow, with sfc temps only expected to reach the teens. These forecast high temps will be very close to the cold max records (see below for specific details on those records).

SDF: 15F, 1914; LEX: 12F, 1917; BWG: 21F, 1985

Sunday night and into Monday will be an even colder night as that strong sfc high pressure moves directly overhead. We'll see single digit temps for just about everyone, and possibly some negative readings across our northern forecast area. However, winds will be much lighter due to the sfc high, so wind chills will be near the sfc temps. However, temps this cold are still impactful, so collaborated with neighboring WFOs to extend the Cold Weather Advisory into Monday as well. We know we won't quite be at advisory criteria Monday morning, but the impacts of a second day of single digit temps warrant the extension.

For the daytime hours on Monday, expect sunny skycover with temps eventually reaching the mid to upper-30s for counties south of I-64. However, for those north of I-64, temps may struggle to get above freezing yet again.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Issued at 343 PM EST Sat Dec 13 2025

Monday Night - Wednesday...

A pattern shift is expected to take place over the first half of the coming week as NW flow aloft flattens out and becomes zonal by mid- week. Monday night into Tuesday, the sfc high which will bring the arctic blast this weekend will be centered over GA, with the cP air mass gradually modifying as we get later into the week. At the same time, a low pressure system and associated polar stream shortwave will slide across the Canadian prairies, strengthening the pressure gradient over the Ohio Valley and bringing warming SW flow into the region. Temperatures should still be below normal Monday night into Tuesday, but the onset of warm return flow should lead to more seasonable temperatures overall, with lows Tuesday morning in the upper teens and low 20s and highs Tuesday afternoon in the upper 30s and 40s across the area. No significant weather is expected during this period, with good chances for sunshine continuing on Tuesday.

Tuesday night into Wednesday, the above-mentioned system over the Canadian prairies will eject across the upper Great Lakes, with a weak upper-level wave over the southern Plains getting picked up and ejecting across the Ohio/TN valley at the same time. While better forcing will be north of our area, there may be just enough combination of moisture and height falls aloft for isolated to scattered rain showers late Tuesday night into Wednesday. Precipitation amounts would be less than one-quarter inch, with most areas seeing little more than extra clouds. Temperatures, particularly lows, will continue to warm Tuesday night into Wednesday.

Wednesday Night - Early Next Weekend...

There is still a strong signal for widespread rain Wednesday night through Thursday night across the region, with modest differences in timing between different model families. An upper-level shortwave and associated sfc low will eject out of southern AB/SK on Wednesday, amplifying and traversing to the E/SE Wednesday night into Thursday. As this system ejects into the Plains, a broad zone of low-mid level S/SW flow will draw moisture out of the Gulf, increasing PWAT values to 1-2 sigma above normal immediately ahead of FROPA. Elevated moisture combined with good lift with the front and the right entrance region of the upper jet should support widespread showers along and ahead of the cold front.

Within the WAA regime, low-level temperature and moisture values start to approach values which would be marginally favorable for thunderstorms, especially if the front passes during the afternoon/evening hours. As would be expected this time of year with almost any strong FROPA, wind shear will be strong/sufficient for severe convection, so we'll have to continue to watch this time period if instability trends upward. For what it's worth, AI/ML severe convection guidance do show a weak signal on Thursday, but it's nothing out of the ordinary for a strong front in the cool season.

In addition to the rain/storms, another impact on Thursday that has pretty good confidence is breezy conditions. Most likely maximum wind gusts from the NBM currently range from 25-40 mph on Thursday, and there is a modest signal for anomalously strong winds in ECMWF EFI data.

Behind the cold front, cooler conditions are likely for Friday as the upper trough and low-level NW flow cross the region. At this time, the ensemble consensus is that precipitation cutoff should be sharp enough to where post-frontal wintry precip appears unlikely/limited. The cool down should also be fairly short-lived as the upper level flow pattern remains progressive and southwesterly return flow returns as we head into the first part of next weekend. While most of the period Friday into Saturday morning should be dry, precipitation chances are favored to return later in the weekend as we remain in a more unsettled weather pattern.

AVIATION /00Z TAFS THROUGH 06Z MONDAY/

Issued at 642 PM EST Sat Dec 13 2025

An arctic cold front will move through the region this evening into early tomorrow morning. As the front passes, a band of snow with IFR VIS which has remained along and north of a BFR-CVG line today will start to sink southward. It is still uncertain how far south this band will make it, with all sites except BWG having at least PROB30 mention of snow to account for this. Generally expecting MVFR CIGs tonight, though occasional drops to IFR are most likely at LEX/RGA. Northwest winds will strengthen behind the front tonight, with a few 20 kt gusts possible. Late tonight, clouds are expected to clear from NW to SE, with sites expected to go VFR by sunrise Sunday. There may be some regeneration of MVFR stratus Sunday morning; however, confidence in whether or not this stratus layer will occur is still fairly low. Winds will remain out of the NW during the day on Sunday, gradually easing by the end of the current forecast period.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Winter Weather Advisory until 7 AM EST Sunday for KYZ030>037- 041>043-049. Cold Weather Advisory from 1 AM EST /midnight CST/ Sunday to 10 AM EST /9 AM CST/ Monday for KYZ023>043-045>049- 053>057-061>067-070>078-081-082. IN...Winter Weather Advisory until 7 AM EST Sunday for INZ076>079- 091-092. Cold Weather Advisory from 1 AM EST /midnight CST/ Sunday to 10 AM EST /9 AM CST/ Monday for INZ076>079-083-084- 089>092.