169 FXUS63 KLMK 120734 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 334 AM EDT Thu Jun 12 2025 .KEY MESSAGES... * Low chances for showers and thunderstorms return this evening across southern Kentucky. * Greater chances for rain, with widespread coverage of showers and storms, are expected Friday into the weekend. Heavy rainfall and localized flooding are the main concerns with storms. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 333 AM EDT Thu Jun 12 2025 This morning, dry and mild conditions continue across central Kentucky and southern Indiana as surface high pressure has gradually drifted over the central Appalachians over the past 12 to 24 hours. Convective debris clouds from showers and storms over the southern Plains continue to drift across the region from southwest to northeast. These clouds and light southeasterly flow have tempered the drop in temperatures slightly compared to previous nights; however, temperatures have still fallen into the low-to-mid 60s in many locations as of 07Z. Regional AWOS/ASOS sites as well as Mesonet cameras show that fog is less widespread and less dense than previous nights; however, still included a mention of patchy fog in the area river valleys through sunrise. Today, a closed upper low centered near OKC this morning will drift to the north and east, approaching the Ozarks tonight. As it does so, combined upper-level and sfc ridging will slide east of the Appalachians, with modest southerly and southwesterly flow spreading across the region. This will bring richer moisture into the area from the Gulf and the lower Mississippi Valley, with dewpoints remaining in the 60s this afternoon. This increase in low-level moisture will make conditions more favorable for precipitation to develop, although warm air in the mid-levels will limit convection today. However, hi-res guidance is hinting at a shower or two popping up across Lake Cumberland and south central KY this afternoon, so we`ll carry a slight chance PoP with this forecast. Temperatures today should be the warmest so far this week, with mid- to-upper 80s expected across the area. 90 degrees can`t be ruled out; however, thickening upper level clouds may limit temperatures. Light southerly winds are expected between 5-10 mph this afternoon. Tonight, as the low pressure system creeps farther to the east, a strengthening height gradient over the region will increase southerly flow, and will also increase low-level moisture. Along the leading edge of a 925-mb theta-E surge, a band of showers and maybe a few storms is expected to develop this evening to our southwest. As we lose daytime heating, this band should weaken; however, scattered showers may make it into areas along and west of I-65 in the early morning hours on Friday. Cloud cover will continue to increase into Friday morning, and a light southeast wind overnight will also help to keep temperatures up. Lows Friday morning will be mild, only falling into the upper 60s and lower 70s. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... Issued at 333 AM EDT Thu Jun 12 2025 Friday through the Weekend... On Friday, synoptic scale upper level troughing is expected across the Gulf of Alaska as well as over the Canadian Maritimes, with broad, flat ridging in place over much of the CONUS. However, a cutoff upper low over the southern Plains today will meander towards the Ozarks and into the mid-Mississippi Valley on Friday along with an associated sfc low. In the vicinity of the cutoff low, a tropical air mass will be present, with PW values expected to range between 1.75-1.9" across the Ohio Valley, with isolated spots around 2". For context, this exceeds the 90th percentile of ensemble climatology in both the Euro and GFS/Canadian ensembles. Model soundings generally show moisture spread through a fairly deep layer, and fairly widespread cloud cover is expected for Friday into the weekend. As a result, instability will be limited, as sounding profiles show "tall, skinny CAPE" which is typically more supportive of efficient rainfall than severe weather. Wet-bulb zero heights in excess of 14 kft will also support efficient warm cloud rainfall processes, and storm motions will be relatively slow, especially Saturday evening into Sunday as the closed low passes over the region. With this being said, the triggering mechanisms for showers and storms will be fairly subtle, and in general, showers and storms should be fairly disorganized given weak to occasionally modest deep- layer shear. Accordingly, while PoPs are fairly high from Friday through Sunday, the weekend shouldn`t be a washout, and there will be significant stretches of dry weather in between rounds of showers and storms. Precipitation coverage will generally be at a maximum during and just after peak heating (i.e., afternoon and evening hours), with lower chances for rain overnight and during the morning. Basin average rain amounts should be around 1" over the weekend; however, there will be considerable variability from location to location, and given the high moisture content and efficient rainfall, localized heavy rainfall amounts are possible, and could result in some flooding. With the moist air mass in place, diurnal ranges will be suppressed, with highs Friday through the weekend generally in the low-to-mid 80s and lows in the upper 60s and lower 70s. Early-to-Mid Next Week... Sunday into Monday, the upper low will gradually get absorbed back into the zonal flow regime over much of North America with the associated sfc low also weakening during this period. PW values will drop somewhat on Monday, and while afternoon/evening showers/storms are still possible, coverage should be less than over the weekend. The pattern will shift slightly as we head into the middle of next week as the upper level jet over the north Pacific is expected to elongate and spread eastward into the Pacific NW. As a result, upper ridging over the desert SW this weekend will spread eastward across the Plains, assisting in bringing height rises across the Mississippi and Ohio Valley. This area of ridging is generally expected to remain fairly flat through next week, with the GFS/GEFS building the ridge across the center of the country more than the ECMWF/EPS. Downstream of the Pacific jet, multiple shortwaves are expected to slide across the northern US through the middle of next week, firing off waves of showers and storms, potentially MCSs. Machine learning severe weather guidance does show a weak signal for strong storms across the Midwest during the middle of next week; however, confidence is low at this time. Depending on how much the ridge builds next Tuesday and Wednesday, our area may see decreasing rain chances or continued waves of showers and storms, with a stronger ridge supporting the drier solution. Regardless, with increasing heights to our southwest, temperatures should increase next week, with highs expected to approach the upper 80s to around 90 by the end of the current extended forecast period. && .AVIATION /06Z TAFS THROUGH 12Z FRIDAY/... Issued at 113 AM EDT Thu Jun 12 2025 Surface high pressure over the Appalachians will bring continued light and variable winds through the morning hours with scattered cirrus streaming into the region from the southwest. Still can`t rule out brief visibility drops from patchy fog around sunrise, particularly at HNB and BWG. Southerly flow of around 5-10 kt will return for the afternoon hours as high pressure moves east. While a few daytime cu may develop in the afternoon, ceilings should remain above 10 kft through the current forecast period, and VFR conditions are expected. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...CSG LONG TERM...CSG AVIATION...CSG