488 FXUS63 KLMK 131456 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1056 AM EDT Fri Jun 13 2025 .KEY MESSAGES... * Waves of showers and thunderstorms are expected today. Heavy rainfall and localized flooding is the main concern, though isolated gusty winds and small hail are also possible. * Additional rounds of showers and storms are expected over the weekend. The potential for severe storms is low, but additional waves of heavy rain may increase the potential for flash flooding. && .UPDATE... Issued at 1055 AM EDT Fri Jun 13 2025 Conditions are warm, humid, and mostly cloudy this morning downstream of a cutoff low over Missouri. Deep SW flow is advecting rich moisture into the region, characterized by PW values of 1.8-2.0 inches. An initial band of showers has been lifting northeast over portions of southern IN and the Louisville Metro this morning, but much of the CWA remains dry. A broader, deeper area of convection is noted on radar and satellite in western KY/TN on the nose of a 35 kt SW low to mid-level jet. Over the next hour or so, these showers and scattered storms will fill in over our counties west of I-65. This activity will lift northeast over portions of central KY and southern IN through mid-afternoon, with additional scattered convection likely just to the east and south of the main precip swath through the evening hours. The main concern remains locally torrential rainfall and flooding given the abundant moisture in place. Cell motion at 20-25 kts will help mitigate the flooding threat, but will need to keep an eye out for any training during the PM hours. Cloud cover is limiting insolation and sfc-based destabilization. In drier areas, temperatures have warmed into the mid and upper 70s. As mentioned in the previous discussion, poor mid-level lapse rates, a tall/skinny CAPE profile, and 20-25 kts of deep-layer shear will limit the severe weather potential. Lightning and localized gusty winds will be possible in thunderstorms (in addition to heavy rainfall). && .SHORT TERM /THROUGH SATURDAY/... Issued at 337 AM EDT Fri Jun 13 2025 The main weather-maker across the Ohio and Tennessee valleys over the next few days is a cutoff upper low which will meander from MO into southern IL today into tonight. Downstream from the center of the upper low, moderate to somewhat elevated 500 mb SW flow on the order of 20 to 30 knots will continue over the region. Deep-layer southerly and southwesterly flow will continue to advect a tropical air mass into the region, with PW values expected to range from 1.75 to near 2". This will all condition the atmosphere for multiple waves of showers and thunderstorms starting today and continuing over the weekend. This morning, a decaying band of showers and storms has lifted into western KY on the leading edge of an 850 mb jet. Later this morning, a secondary LLJ is expected to push across western TN and KY, helping to spark additional waves of showers and storms for the late morning and afternoon. As these waves of showers and storms push into central KY and southern IN, dewpoint temperatures are expected to rise into the upper 60s and lower 70s, with air temperatures rising with daytime heating later this morning. Exactly how much heating occurs is uncertain, and will be limited by increasing low- and mid-level cloud cover, especially west of I-65. As a result, temperatures should be a few degrees cooler in most locations today, with highs expected to range from near 80 west of I-65 to the mid 80s along the I-75 corridor. The combination of ingredients for thunderstorms this afternoon is modest. Instability progs show between 1400-1800 J/kg MLCAPE, though poor (~5 C/km) mid-level lapse rates will result in a "tall, skinny CAPE" profile which is less favorable for explosive updrafts. Effective bulk shear values are expected to be around 20-25 kt, so one or two organized clusters of storms is possible. Low-level shear is weak, so rotating updrafts are unlikely with today`s storms, although it should be noted that a subtle sfc boundary is expected to lift through the area today, with backed winds likely in the vicinity of this boundary. All in all, the severe potential appears to be limited, though isolated instances of strong wind gusts and small hail is certainly possible. Heavy rainfall and isolated flooding will be of greater concern, and the 00Z HREF localized probability-matched mean QPF field does show a few swaths of 2-4" across the area this afternoon. As instability wanes this evening into tonight, the coverage of showers and storms will diminish. With that being said, continued warm/moist advection within 20-25 kt of SW flow at 850 mb should support at least isolated to scattered showers overnight. The saturated air mass will limit cooling, with low temperatures Saturday morning only expected in the upper 60s and lower 70s. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 337 AM EDT Fri Jun 13 2025 This Weekend... Unsettled weather is expected to continue over the weekend as the upper low gradually weakens and moves across the Ohio Valley. With no significant changes in the synoptic flow patterns, the tropical air mass should remain in place, with PW values remaining between 1.8-2". Although there will be plenty of near-sfc moisture, elevated moisture content through the troposphere and continued poor lapse rates will limit instability. As the upper low moves nearly overhead, deep-layer shear and mean winds will weaken, further reducing the potential for organized/severe storms while increasing the potential for slow moving/heavy rainfall amounts. Fortunately, the lack of organization will keep shower/storm development fairly random, though any locations which receive multiple waves of storms over the weekend could see flash flooding. Diurnal temperatures will be suppressed by increased cloud cover and the muggy air mass, with highs expected in the low-to-mid 80s and lows in the upper 60s and lower 70s. Next Week... There is growing consensus in a decrease in shower/storm activity for Sunday night into Monday as the remnant energy from this weekend`s system dissipates and lifts to the northeast. The continued humid air mass will still keep a chance for afternoon showers and storms on Monday, but coverage should be more isolated than over the weekend. For the middle and latter portions of next week, split upper-level flow will develop across much of the CONUS downstream of the Pacific jet which will extend into the northwestern US Monday into Tuesday. This will allow a couple shortwaves to slide across the northern half of the US within the broader zonal flow pattern. As these waves pass by just to the north of the region, they should fire off additional waves of showers and thunderstorms. While there should be considerable gaps between waves of showers and storms, confidence in timing these waves is only low-medium at this point, so we`ll have to keep an ongoing elevated PoP in the forecast for much of next week. Stronger signals for showers and storms are present Tuesday afternoon and evening and again on Thursday, though this may change as additional guidance comes in over coming days. Each of these waves of storms would carry a potential for stronger wind gusts given a pattern which is somewhat favorable for MCS development; however, confidence in this is also low. Temperatures will gradually warm next week, although the current forecast is only a few degrees above normal for mid June. && .AVIATION /12Z TAFS THROUGH 18Z SATURDAY/... Issued at 656 AM EDT Fri Jun 13 2025 There is fairly low forecast confidence beyond the first few hours as multiple waves of showers and thunderstorms are expected to move across area terminals later today. Outside of showers and thunderstorms, VFR conditions should be prevalent, though IFR/MVFR ceilings and visibilities will be possible with heavier showers and thunderstorms. Generally speaking, the greatest concentration of showers and storms should be between 17-00Z, with coverage decreasing after sunset tonight. Winds will be light out of the south today, backing to the southeast later this afternoon and into the evening. Tonight, VFR conditions are expected to continue, though model guidance hints at falling ceilings from north to south during the early morning hours on Saturday. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...EBW SHORT TERM...CSG LONG TERM...CSG AVIATION...CSG