962 FXUS63 KLMK 121554 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1054 AM EST Sat Jan 12 2019 .Forecast Update... Issued at 1054 AM EST Sat Jan 12 2019 Area radars showing main band of precipitation continues to lift northward into central Indiana this morning. Further south across KY, there is secondary band of light precipitation moving northward. The band currently extends from near Owensboro to just north of Somerset. This band should continue to move northeastward through the rest of the morning hours. The band appears to be associated with some sort of warm front boundary. It's not characteristically defined in terms of wind direction on either side, but temperatures south of this boundary have increased by some 3-4 degree after its passage. Temperatures across southern KY have warmed to around 40 while areas mainly north of the I-64 corridor remain just below freezing. In the near term, we expect to see just some scattered precipitation lift northward through the area for the remainder of the morning and into the afternoon hours. Temperatures look to rise slowly through the afternoon. Current thinking is that we'll top out in the mid- upper 30s across the far north, with upper 30s to the lower 40s across much of south-central KY. There is a noticeable spread in the short term guidance for temps this afternoon. The 3KM NAM generally keeps us near the aforementioned temps for the afternoon given a generally neutral advection pattern. Having east/northeast winds in here would not support much of a rise in temps. The HRRR surges temps into the mid-upper 40s, but this because the model flips winds around to the south/southeast advecting much warmer air into the region. Current obs from the Mesonet do not support the switch to SE winds yet. However, its not out of the realm of possibilities that we could see some places near the KY/TN border region down near Lake Cumberland to surge later this afternoon, especially if we get some mixing and a little bit of sunshine. There is some filtered sunshine down in the TN plateau right now. So, we'll keep an eye on that. With regards to the warning and advisories, we're all above freezing across our Kentucky counties, and just a few spots in our northern row of southern IN counties are just approaching freezing. We're not expecting much in the way of additional wintry weather with this wave, so probably will be canceling the warning and advisories prior to planned expiration. Issued at 852 AM EST Sat Jan 12 2019 Based on Kentucky Mesonet and NWS observations, the freezing line current extends rough along and just north of the I-64 corridor in southern IN and into portions of north Central KY. It then arcs a little southward in the I-75 corridor. Within the sub-freezing area, precipitation production continues with mainly a mix of sleet and freezing rain. Overall, the snow production with this system is likely only effecting our northern row of southern IN counties at the moment. Elsewhere, mainly south of the WK and BG Parkways, the precipitation is plain rain and conditions are improving at a good clip. Looking at webcams from southern KY, almost all the roadways are clear, though there could be some slick spots on the backroads in some areas. Here in the metro, crews are generally working on side streets now as the main roads are in good shape. Conditions within the Louisville metro area will continue to sharply improve as temps continue to warm above freezing. Across southern IN, a mix of sleet/freezing rain/snow will continue for the next several hours. Accumulations will be possible up this way, though they look to be very minor. With temps below freezing, hazardous driving conditions will likely remain in place through lunchtime with good improvement in the afternoon hours. In the Bluegrass region, we've seen precipitation change over to a mix of sleet and freezing rain. We're likely to see this oscillate back and forth a bit until surface temps go above freezing which should occur over the next few hours. With that said, have gone ahead and let the southern tier of the Winter Weather Advisory go prior the 900 AM EST expiration. Will keep the northern tier of the Advisory going until noon EST. However, if conditions continue to improve, I can see dropping this advisory earlier. For now, will be leaving the Winter Storm Warning in place, though I also can see that product getting dropped earlier than its original expiration as well. && .Short Term...(Today and tonight) Issued at 259 AM EST Sat Jan 12 2019 Wintry weather is ongoing this morning across most of the region. The greatest snow accumulations have generally been confined to parts of southern Indiana and north-central Kentucky west of the I- 65 corridor, where 1" to 2" of snow have fallen based on reports within the past hour or so. Regional radars show a decrease in activity and coverage at this hour across western and south-central Kentucky. Looking at model soundings, think this is due to some drier and warmer air aloft. There is some concern we could see periods of freezing rain and/or sleet as far north as southern Indiana as this drier and slightly warmer air move in aloft. Freezing rain has already been reported across portions of south-central Kentucky this morning, and ASOS's in extreme western KY and southern IL have been reporting UP (unknown precip). Any ice that does fall on top of the current snowpack in southern IN and north-central Kentucky will only make travel that more dangerous. On the note of warnings/advisories, the current expiration times and areal extent look good. There is some concern we may not hit warning criteria snowfall (4") in our southern Indiana counties, but it could end up being a close call in some areas when all is said and done, so will just let it ride out for the time being. Wintry precipitation should gradually transition to rain this morning across all of central Kentucky, and southern Indiana by early afternoon. Models indicate multiple rounds of precipitation through the morning and afternoon hours, so while it won't be precipitating all day long, its very likely that most areas in the region will see something at some point. More widespread precipitation is forecast to move in tonight, mostly in the form of rain. The exception will be southern Indiana, where model soundings are borderline rain/snow. Will have to watch this area closely, as differences in temperature of a degree or two could result in a much snowier scenario in southern Indiana and parts of northern Kentucky. .Long Term...(Sunday through Friday) Issued at 258 AM EST Sat Jan 12 2019 On Sunday weakening low pressure will move across the Tennessee Valley as high pressure ridges from the Great Plains to the Saint Lawrence Valley. Moisture and lift will gradually decrease as we go through the day, but light precipitation is still likely north of the surface low and just ahead of a 5H trough. Most of the precipitation in the morning should be rain, but a light wintry mix will still be possible north of Interstate 64 where there still may be some moisture in the DGZ along with an isothermal layer sfc-800mb right along or very near the 0C line. By afternoon all areas should be warm enough for light rain (scattered) with highs ranging from the mid 30s in southern Indiana to the mid 40s in southern Kentucky. Sunday night through Monday low level moisture will get trapped under a low-level inversion, mostly below the DGZ. NNE winds off of the aforementioned ridge settling into the Ohio Valley will provide cold air, especially below 850mb. Lift should be about nil, but some patchy freezing drizzle isn't out of the question in the morning, especially east of Interstate 65 where moisture will be a little deeper. Monday night through Tuesday night will be dry as the high progresses from the Ohio Valley to the Southeast. Tuesday morning will be chilly with southern Indiana and the northern Blue Grass probably dipping into the teens. Wednesday a weakening cold front will approach from the west, reaching Kentucky by evening, and then possibly remain in the area as small ripples move through quasi-zonal flow aloft. Confidence is low concerning if and when any of these features might produce precipitation. Will keep PoPs and QPF low, in agreement with GEFS ensemble members and other models. Better chances for significant precipitation will arrive for the weekend. && .Aviation...(12Z TAF Issuance) Updated at 558 AM EST Sat Jan 12 2019 Precipitation is slowly transitioning from wintry (snow, sleet, freezing rain) to a plain, cold rain this morning. Warmer air is working northward from south-central Kentucky, and we should see north-central Kentucky and southern Indiana transition to rain later this morning. A corridor of IFR/MVFR cigs roughly along and north of the Bluegrass Parkways will lift northward this morning, though how far north it lifts is a bit uncertain. Most model guidance has it hovering around the I-64 corridor today, but if it lifts farther north than forecast, HNB/SDF/LEX could see VFR cigs for a good portion of the late morning and early afternoon timeframe. Current forecast leans toward model consensus, but something to watch closely today. Another round of precipitation will knock down cigs/vis across the region later this evening for all TAF sites. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...Winter Storm Warning until 1 PM EST this afternoon for INZ076>079-083. Winter Weather Advisory until noon EST /11 AM CST/ today for INZ084-089>092. KY...Winter Weather Advisory until noon EST today for KYZ025-029>043- 048-049-057. && $$ Update.......MJ Short Term...DM Long Term....13 Aviation.....DM