822 FXUS63 KLMK 240006 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 706 PM EST Sat Jan 23 2021 ...Updated Aviation Discussion... .Short Term...(This evening through Sunday) Issued at 300 PM EST Sat Jan 23 2021 ...Freezing Rain Expected Tomorrow Morning... Surface high pressure is beginning to get pushed off to the east. Clear skies will hold on until a few hours after sunset. This will allow radiative cooling to quickly drop temperature early tonight, and this will become part of the equation for our next system. The main focus for the short term is the chance for freezing rain tomorrow morning. The CWA will sit under the right front entrance region to an upper level jet. Low level forcing is expected to respond, and precipitation chances will begin to increase as sunrise nears tomorrow morning. Based on last night's data, a winter weather advisory was going to be in the works, but this morning's data came in showing a delay in the onset of precipitation. Several models are showing less freezing rain. Looking at the data, it all shows a warm nose above the surface and surface temperatures below freezing. Confidence is reduced after looking at moisture profiles. Moisture builds in between 650 and 850 mb, but below that, it's dry. In time, this layer will saturate. If saturation can overcome the dry air, temperatures will cool towards the wet bulb. This would help further freezing rain (and limited snow), but if moisture can't overcome this dry air until surface temperatures climb above freezing, regular rain falls. Believe the dry air will become saturated and freezing rain will result, but believe most of the precipitation will arrive near the above freezing temperatures. Freezing rain will be limited. Believe the best location for freezing rain in our CWA is north of the Ohio River and west of Interstate 65. In this area a tenth of an inch is possible. Outside of this area down to a line from Elizabethtown, KY to Lexington, KY, 5 hundredths of an inch is about max with most only seeing 1 to 2 hundredths. After collaborating with surrounding offices, Louisville, Paducah, and Indianapolis will continue with Special Weather Statements for the potential freezing rain tomorrow morning. As data comes in, this could still be upgraded to an advisory by a later shift. For the rest of the day, light rain will continue for many across the CWA. Most of the rain is expected to cut across the center of the CWA from west to east. Up to 3 tenths of an inch is expected. High temperatures will spread from the upper 30s near Madison, IN to near 50 along the Tennessee border. && .Long Term...(Sunday night through Saturday) Issued at 250 PM EST Sat Jan 23 2021 ...Widespread Soaking Rains Late Sunday Night and Monday... Dynamic and progressive upper trof will kick out of the Sonoran Desert Sunday night, developing a sfc low over Texas and lifting a warm front northward through the Tennessee Valley. Isentropic lift ahead of the front will spread steady rains into Kentucky after midnight Sunday night. Intensity of precip will increase through the day on Monday as the low-level jet cranks up to around 60 kt at 850mb. There's a small chance for thunder given the strength of the LLJ and some weak elevated instability, but temp profiles will keep most of the stronger winds from mixing down, so SVR potential is minimal. Bigger story will be rain, with QPF pushing 2 inches for some during the day on Monday. Will need to keep an eye on where the axis of heaviest rainfall sets up, as 6-hr Flash Flood Guidance is barely over 2 inches for some areas east of I-65, especially down toward Lake Cumberland. Depending on the placement of the heaviest rainfall, longer-fuse river flooding could become an issue toward the middle of the week, with the greatest emphasis at this time on the Green River. Otherwise we'll be looking at a sharp temp gradient somewhere near the Ohio River, with afternoon highs just cracking 50 north of the I- 64 corridor while south-central Kentucky gets into the 60s. Tremendous bust potential along/north of the Western Kentucky and Bluegrass Parkways, as the band of 50s will probably be narrower than we show in our official forecast grid. Next system comes in late Wednesday/Wednesday night, with a progressive trof developing a sfc low over the Deep South. This can be a somewhat favorable low track for accumulating snows, and the nocturnal timing also favors snow, but having cold air in place is a bigger question. Not much confidence at this point but there is a decent chance for minor accumulations north of I-64. Ridging builds over the Plains late in the week and migrates eastward, so we'll have a period of dry weather and above normal temps before the next system arrives late Sat. && .Aviation...(00Z TAF Issuance) Issued at 705 PM EST Sat Jan 23 2021 After VFR conditions for the next several hours, conditions will deteriorate significantly. Increasing low and mid level jet energy combined with weak moisture advection into the region from the mid-Mississippi Valley overnight will lead to increasing clouds and eventually light precipitation by morning. Soundings show a warm layer with temperatures in the upper 30s just a few thousand feet off the ground while surface temperatures hover right around or slightly below freezing. So, will continue mention of light freezing rain at onset Sunday morning. There is the potential of ice crystal generation aloft and with dry sub-cloud air and wet bulbing below the warm nose some ice pellets aren't out of the question. HNB and SDF stand the best shot at seeing the light wintry mix. As temperatures warm after sunrise the early morning wintry precipitation will transition to scattered plain rain. Coverage of the rain will gradually decrease during the afternoon as weak upper ridging moves in. We'll hold on to low clouds, though, with some patchy drizzle possible. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...KDW Long Term...RAS Aviation...13