Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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031 FXUS63 KLMK 041419 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1019 AM EDT Thu Jul 4 2024 .KEY MESSAGES... * Scattered thunderstorms are forecast today, and thunderstorms will be capable of torrential downpours, gusty winds, and intense lightning. * Isolated flash flooding is possible today, especially across portions of southern Indiana and the Louisville Metro where heavy rain occurred yesterday. A Flood Watch is in effect for the most vulnerable locations. * Unsettled weather will continue through Friday with daily chances of showers/storms. Isolated damaging wind gusts, torrential rainfall, and lightning will be the primary hazards. && .UPDATE... Issued at 1019 AM EDT Thu Jul 4 2024 Washed out frontal boundary is situated over southern Indiana this morning. This boundary is expected to push north some today, keeping most of the widespread precip north of the region. Already this morning, a line of heavy rain moved through southern Indiana bringing an additional 1-1.5 inches of rainfall. Some CoCoRaHS sites in Dubois County have reported 4-5 inches of rain in the last 24 hours. Our far northwestern counties will continue to see low Flash Flood guidance through today, therefore there is a Flood Watch in these areas. The HRRR and RAP have initiated and handled this mornings convection well. These models keep showers and storms isolated through the afternoon and increasing in coverage in the late afternoon through the evening. Other guidance has development over northern Kentucky and southern Indiana mid-day through the evening. Forecast confidence remains low as there are multiple factors at play... atmospheric recovery over southern Indiana after multiple rounds of rain, cloud coverage, and frontal boundary placement. High confidence remains in very moist conditions through the overnight. If we do get development, we will see an additional 1-2 inches of rain with locally higher amounts possible. If the region does stay drier through the early afternoon, strong to severe weather potential will increase in the afternoon through the evening. Given ample instability, moisture, little shear, and present MCV, gusty to damaging winds and torrential rainfall will be possible. Additionally, with MCV increasing low level shear, there is a very low, but non-zero tornado threat. Over central and southern Kentucky, mostly clear skies and afternoon diurnal Cu development will allow for ample heating. Could see scattered storms and isolated strong to severe storms in the later afternoon after reaching convective temps. Shear is very weak, therefore, pulse storms would be lead to a gusty wind, heavy downpour, and a lightning threat. Independence Day festivities... use caution while recreating and stay weather aware today. && .SHORT TERM /THROUGH TONIGHT/... Issued at 408 AM EDT Thu Jul 4 2024 Precip coverage has decreased considerably early this morning with just some very isolated activity. Earlier convection has weakened with more stable air near the surface. A stalled, washed out frontal boundary extends from southern MO ENE through the OH Valley. An extremely moist airmass remains in place, characterized by 2.0-2.3 inch PW vales and sfc dewpoints in the mid 70s. The key to the forecast today is upstream convection in KS/MO and how it evolves. A MCS is forecast to push ENE across MO and into the Lower OH Valley later this morning. The overall convective complex should weaken with time, and organized severe weather does not appear likely. At this time, we expect increasing thunderstorm chances by mid to late morning along and north of the I-64 corridor. Convection should continue to push east across the northern half of the area from mid- morning into early afternoon. By midday or early afternoon, additional scattered storm development becomes more likely along the southern flank of morning convection/convective outflow. This will allow thunderstorm chances to increase in central and southern KY this afternoon and evening. However, forecast confidence in detailed evolution drops beyond early afternoon. This morning, a swath of heavy rain appears possible across southern IN - including areas that saw flash flooding yesterday with the first round of convection. An additional 1-2 inches of rain is possible with locally higher amounts likely with any training storms. Given the now lower FFG in these more vulnerable areas, a Flood Watch has been issued in southern IN extending east into the Louisville Metro through this evening. Localized flooding issues will still be possible today outside of the Flood Watch area. However, HREF PMM QPF supports a greater than 50% chance for at least 1 inch or more of rain in 3 hours this morning/early afternoon in areas that received the heaviest rainfall yesterday. Scattered storms will likely linger in central KY into the evening hours before activity diminishes once again in both coverage and intensity. A lull is then expected through the first half of the overnight period. Rain chances ramp back up heading into early Friday as a deeper wave of low pressure moves across the Midwest. Partly to mostly cloudy skies will help keep temps in check to some degree today. Afternoon highs are expected to range from the mid 80s to lower 90s. Southern KY will see a drier first half of the day and is more likely to see widespread low 90s by the afternoon. Heat index values will likely creep back above 100 degrees this afternoon in south-central KY. Scattered storms will then bring some relief from the heat and humidity to some. Heat index values may approach 105 in a few spots, but confidence is not high given the very humid environment and potential for clouds/rain during peak heating. Will therefore issue an SPS for south-central KY to highlight the elevated heat and humidity. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Issued at 408 AM EDT Thu Jul 4 2024 Friday through Sunday Night... Surface frontal boundary will be in the vicinity of the CWA Friday morning. We may have one or more perturbations aloft move through sparking one or two more rounds of showers/storms during the day on Friday. However, a stronger upper level wave moving across the Great Lakes will send a cold front through the region Friday night ending precipitation chances. Convective evolution for Friday remains a bit uncertain given that we may have ongoing convection early in the day which may hinder afternoon insolation. While we`ll have a moist airmass in place, MLCAPE values could rise into the 1000-1500 J/kg range with about 25-30kts of shear. Overall coverage from the latest CAMs looks to be more sparse across our region with a relative maxima possible over OH/PA where bulk shear values would be larger. Any storm could produce gusty winds, intense rainfall along with plenty of lightning. Highs on the day may be kept down a bit by ongoing cloud cover, but readings in the mid-upper 80s look likely. After the cold front passes through, some cooler/drier air will work into the region with lows Friday night dipping down into the low-mid 60s. For Saturday/Sunday, dry conditions with near normal temperatures are expected across the area. Dewpoints will be noticeably lower with readings in the lower-middle 60s. Highs Saturday will be in the mid 80s (83-88) with overnight lows in the upper 50s to the lower 60s. Sunday should feature slightly warmer conditions with highs mainly in the upper 80s. Lows Sunday night will dip back into the mid-upper 60s. Monday through Wednesday... As we head into next week, upper level pattern will change quite a bit as strong ridging builds across the far western US with a longwave trough develops across the eastern US. Tropical cyclone Beryl looks to make land fall across Mexico/S Texas early in the week and some of the remnant moisture may get pulled back to the north and northeast into the Ohio Valley by mid-late week. Decent upper level wave looks to push through late Tuesday bringing a good shot of showers/storms. Overall, generally kept PoPs in the extended in the 30-40% with the exception of Tuesday where we`ll run 50% PoPs. Highs on Monday will likely be the warmest of the period with readings in the upper 80s to the lower 90s. Tuesday and Wednesday look to feature highs mainly in the upper 80s with overnight lows in the upper 60s/lower 70s. && .AVIATION /12Z TAFS THROUGH 18Z FRIDAY/... Issued at 652 AM EDT Thu Jul 4 2024 Scattered showers and storms are likely this morning, especially along the I-64 corridor. This activity could bring brief TSRA impacts to HNB and SDF early in the forecast period. Rain and thunderstorm chances will gradually increase further south and east late morning into the afternoon hours. Outside of convection, prevailing VFR is expected. Confidence in detailed timing for TSRA remains rather low due to some uncertainty regarding exact coverage and evolution. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Flood Watch until 8 PM EDT /7 PM CDT/ this evening for KYZ023>025-030. IN...Flood Watch until 8 PM EDT /7 PM CDT/ this evening for INZ076- 083-084-089>091. && $$ UPDATE...SRM SHORT TERM...EBW LONG TERM...MJ AVIATION...EBW