Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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326 FXUS63 KLMK 230548 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 148 AM EDT Mon Sep 23 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Multiple waves of scattered showers and storms are expected this afternoon through Tuesday night. There is a low chance for strong to severe storms Monday and Tuesday. * Unsettled weather is a possibility into late week with the remnants of a tropical system potentially moving into our region. && .UPDATE... Issued at 935 PM EDT Sun Sep 22 2024 Mesoscale analysis reveals a weak frontal boundary currently bisecting the region. Scattered showers are occurring out ahead of this boundary from roughly Lexington southwest toward the Bowling Green area. Instability continues to wane, but we still have about 1000-1250 J/Kg of MLCAPE, but MLCINH continues to increase as the boundary layer cools. PWATs are quite high with most areas seeing values in the 1.75-2.0 inch range. In the short term, cluster of showers and embedded storms will continue to move eastward, mainly along and south of the WK Parkway affecting the Bowling Green area over the next 1-2 hours. Severe weather is not expected, however, brief heavy rainfall, wind gusts to 30-35 mph, and frequent lightning can be expected as this activity pushes east. The environment east of I-65 is more convectively hostile, so this activity should weak considerably as it goes into southern KY. For the overnight period, low-level moisture trapped below an increasing inversion aloft will lead to widespread low status and the potential for fog development. The fog could be locally dense in areas, especially those that so appreciable rainfall today. && .SHORT TERM /THROUGH TONIGHT/... Issued at 333 PM EDT Sun Sep 22 2024 This afternoon and evening... Sensible weather across the area is quite variable this afternoon. Across much of southern IN and north central KY, clouds and light rain showers have led to a more stable, cooler environment with temperatures generally in the upper 70s and lower 80s. Along and south of the western KY/Bluegrass Parkways, more sunshine and heating this morning has allowed temperatures to warm into the upper 80s and lower 90s, with scattered showers and thunderstorms developing in an increasingly unstable environment. As we head later into the afternoon and evening, recent high resolution guidance suggests that much of the northern half of the FA will be stable enough to preclude convective re-development, with just isolated to scattered light rain showers continuing into the evening hours. For the southern half of the FA, we`ll have to watch an area near the confluence of the Wabash and Ohio Rivers for development of showers and storms, as there is a strong differential heating boundary left over from clouds and showers/storms earlier today. Any stronger storm could produce gusty winds and small hail, though widespread strong/severe storms are not expected. Any convection should begin to dissipate by around 02Z tonight, though isolated showers may continue into the overnight. Tonight... A surface cold front will settle across the area tonight, with pooling moisture and light winds expected across the region. This combination of ingredients will allow for either low stratus, fog, or a combination of both, as near-sfc winds are expected to be just light enough to allow stratus to settle into fog. Coverage of rain showers should decrease through the nighttime hours, with most locations remaining dry into early Monday morning. Low temperatures will be mild for late September, with lows ranging from the mid 60s to the low 70s Monday morning. Monday... Tomorrow morning, the initial upper-level trough which brought the sfc cold front into the region this afternoon will lift off to the northeast of the region, as a secondary upper shortwave lingers back over the central Plains. As a result, the sfc front should become quasi-stationary and eventually begin to lift back to the north by tomorrow afternoon as the next upper wave approaches from the west. As a result, ample moisture will remain over the region, leading to mostly cloudy or even overcast skies across most of southern IN and central KY. The primary forecast question for tomorrow will be how much, if any, destabilization we see, as continuing low cloud cover will make it difficult to get much surface heating. 12Z HREF guidance has the highest amounts of CAPE tomorrow afternoon along and south of the western KY/Bluegrass Parkways, with probabilities of greater than 40 dBZ Reflectivity highlighted in these areas as well. With deep-layer shear expected to be around 20- 25 kt, one or two strong storms will be possible, with gusty winds and small hail being the primary severe hazards. North of wherever storms develop, light to moderate rain will be possible, though a lack of instability should preclude the development of thunderstorms. Temperatures Monday afternoon will vary from north to south, with upper 70s and lower 80s expected in north central KY and southern IN, while mid- and upper 80s will be possible in southern KY. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Issued at 333 PM EDT Sun Sep 22 2024 ===== Monday Night - Wednesday ===== A shortwave trough embedded within a larger central CONUS trough will rotate from the lower Missouri/mid Mississippi River Valleys up into the Great Lakes Monday night through Tuesday. Meanwhile, an associated surface low takes a similar path. As the surface low moves by to our north and east, we`ll see the quasi-stationary frontal boundary that had been draped over our region try to lift north as a warm front. How much of a warm sector gets established over our area remains to be seen, but much will depend on the strength of the surface low, of which there is still some spread in guidance. Regardless, there there looks to be plenty of forcing and available deep moisture for scattered showers and a few storms overnight, and then better coverage of showers and some storms Tuesday morning just ahead of the main shortwave trough axis and surface cold front. This mainly morning timing may play to our favor as we don`t appear to get a whole lot of instability in here, and given an uptick in the deep layer shear profile could be the limiting factor to a larger severe weather concern. Can`t rule out some stronger storms, especially if a stronger surface low scenario ends up being reality, but too early to have a whole lot of confidence just yet. Something to watch. Later Tuesday into looks to be overall dryer in the wake of the shortwave and post-frontal regime. That being said, may have to hang onto some lingering shower chances across our far south and east as the frontal boundary hangs up down there and a renewed source of moisture transport develops on the east side of an Ozark region closed low. Temps should generally run in the upper 70s and low 80s into mid week. ===== Thursday - Sunday ===== Quite a bit of uncertainty with respect to the late week/weekend forecast. Much will depend on the interaction between a likely tropical system coming out of the Gulf and the aforementioned closed low. A third complicating feature will be a blocking ridge between the two systems to our southeast and a third closed low over eastern Canada and New England. This complex interaction between all parties makes for a tricky and very low confidence forecast at this time. There has been a sporadic PRE type of event that shows up in various deterministic runs from time to time, all the way to a pretty much dry late week and weekend as the blocking ridge becomes our dominant feature. Right now, could go either way, or more likely something in between. For now, will keep chances for rain in every day with temps in the upper 70s and low 80s. Stay up to date of the latest forecasts as details become more clear. && .AVIATION /06Z TAFS THROUGH 12Z TUESDAY/... Issued at 148 AM EDT Mon Sep 23 2024 A weak sfc boundary is draped southwest through the Lower Ohio Valley early this morning. Isolated SHRA and a couple storms are ongoing east of I-65 and will be near LEX to begin this TAF period. However, the main aviation impact this morning will be a period of MVFR stratus and perhaps some fog in any areas where clouds briefly scatter out. MVFR stratus will increase in coverage and become more common between 06-09Z, with impacts lingering through 12-15Z. This afternoon, expect SCT TSRA with associated brief impacts possible - heavy rainfall, lightning, locally gusty winds. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...MJ SHORT TERM...CSG LONG TERM...BJS AVIATION...EBW