Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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972 FXUS63 KLMK 080731 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 331 AM EDT Sat Jun 8 2024 .KEY MESSAGES... * Showers and a few thunderstorms this weekend, with extended breaks in the rain expected. Locally heavy downpours possible late Saturday night into early Sunday morning across western and southern Kentucky. * Temperatures will begin a warming trend Tuesday, with 90 degrees a possibility by late week, especially Friday. && .SHORT TERM /THROUGH TONIGHT/... Issued at 330 AM EDT Sat Jun 8 2024 Across the region early this morning, mostly clear skies are observed on latest nighttime microphysics satellite imagery, with the first few convective debris clouds from an ongoing MCS over eastern KS and western MO reaching our area at this time. As we head toward dawn, additional clouds will begin to move toward the region as the convective system moves eastward. This system should weaken considerably as it loses its source of instability; however, an area of light to moderate rain showers will approach areas west of I-65 by the mid-to-late morning hours. Since the pre-existing air mass over our area is abnormally dry, would expect initial radar returns to struggle to make it to the ground later this morning. While current analysis and short range progs do show increasing PWAT values later today, inspection of the moisture profile via hi-res soundings reveals that much of this moisture increase will take place above 700 mb, with the lowest 10 kft being slow to saturate. Accordingly, have lowered PoPs from NBM guidance, though this still leaves chance PoPs across much of the area later today. PoPs generally decrease the farther south and east you go, given that the remnants of the MCS should be falling apart as they move east across central KY and southern IN. With the additional mid- and upper-level moisture present, mostly cloudy skies are expected for much of the day today. Clouds are expected to keep temperatures in the mid-to-upper 70s outside of southern KY, though there is a low confidence possibility that brief breaks in the clouds later this afternoon could allow temperatures to quickly surge up into the 80s (10-20% likelihood). With the sfc high pressure axis shifting to the southeast U.S. later today, SW winds on the order of 5-10 mph are expected during the daytime hours. This evening into tonight, an upper-level shortwave moving through the upper Midwest will help to push a sfc cold front into the region from the north. To the west of the region, waves of convection are expected to initiate over central MO as convergence and lift in the vicinity of the aforementioned front combines with a quite unstable air mass over the Ozarks. Once this convection fires up, it should move to the ESE along with deep-layer flow, taking it into the lower Ohio and Tennessee valleys. Early Sunday morning, rain showers and embedded thunderstorms should begin to move into the region, with latest guidance generally favoring a track into southern KY and TN. These convective complexes should be weakening as they move east of the greatest instability; however, these showers and storms could still produce areas of heavy rainfall, though exact positioning is somewhat uncertain. 00Z HREF rainfall LPMM has swaths of greater than 1" QPF over portions of southern KY, though this does appear to be driven largely by one (HRRR) solution. Farther to the north, light to moderate rain showers will be possible late tonight, with rain chances falling off precipitously as you get north of I-64. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 330 AM EDT Sat Jun 8 2024 Sunday... Cold frontal passage from north to south will take place on Sunday, accompanied by showers and a few thunderstorms. QPF is highest over southern Kentucky where there will be the longest residence time of shower activity ahead of the front, and where there could be some locally heavy downpours in rich PWAT air. Rest of the week... On Monday an upper trough reaching from the Canadian Maritimes to the Ohio Valley will pass overhead. There should be very little moisture for this system to work with and a strong mid-level cap will be in place, so right now the forecast calls for partly cloudy skies and no more than perhaps a stray low-topped light rain shower along/east of I-75. Tuesday through Thursday continue to look dry as high pressure translates from the Midwest to off the mid-Atlantic coast and the main storm track is well to our north along the Canadian border. Temperatures will moderate from highs Tuesday in the middle and upper 70s to the middle and upper 80s Thursday as we get into return flow behind the departing surface high along with increasing 1000- 500mb thicknesses. A cold front may approach by Thursday night or Friday, but uncertainty is great this far out in the forecast and most ensembles and operational runs keep us dry with the main sources of available moisture to our south over the Gulf and our north over the Great Lakes, so will stick with a dry forecast here for now. && .AVIATION /06Z TAFS THROUGH 12Z SUNDAY/... Issued at 141 AM EDT Sat Jun 8 2024 High clouds from a convective system over the central Plains will begin to move across the region over the next few hours, with winds remaining light and generally out of the SW through sunrise. Later this morning, the remnants of the convective system are expected to move across the region as a weakening band of light rain showers. Little to no impacts are expected from these showers, and due to coverage and timing uncertainty, we`ll only go with VCSH mention for now. A light SW breeze should pick up after sunrise this morning, with wind speeds of 5-10 kt expected through the daytime hours today. Cloud bases will gradually build downward through the day, though there is high confidence in VFR conditions continuing through at least the late evening hours tonight. Toward the end of the current forecast period, a cold front dropping in from the north will bring an increase of moisture below 10 kft. At this time, we`ll keep VFR CIGs going through the forecast, although the probability of MVFR or lower CIGs will increase between 06-12Z Sunday. Additionally, a second round of rain (and possibly a few storms) may impact sites early Sunday morning; however, confidence is too low to mention in the current forecast. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...CSG LONG TERM...13 AVIATION...CSG