Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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823 FXUS63 KLMK 091404 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 1004 AM EDT Sun Jun 9 2024 .KEY MESSAGES... * Scattered showers and isolated thunderstorms today in south central Kentucky. Severe weather is not expected. * Below normal temperatures and humidity Monday and Tuesday, followed by a warming trend with hot and dry conditions likely for late this week into next weekend. && .UPDATE... Issued at 1004 AM EDT Sun Jun 9 2024 Cold front now just south of Interstate 64 and continuing to make slow but steady southward progress. Dewpoints behind the front are dropping into the upper 50s, and any showers incoming from the west are being deflected well south into south-central Kentucky. Think precip chances for the balance of the day will be limited to south of the Parkways, with isolated to scattered coverage at best. Diurnal temp curve will be a bit delayed, but still believe we can get to forecast max temps this afternoon. Changes to the going forecast will be more in the hourly details, but the update will be on the way shortly. && .SHORT TERM /THROUGH TONIGHT/... Issued at 305 AM EDT Sun Jun 9 2024 At 06Z a surface boundary stretched from central Ohio through southern Indiana to southeast Missouri. This will push southward across Kentucky this morning, possibly accompanied by scattered showers south of Interstate 64. Lapse rates will be weak and soundings don`t indicate much in the way of instability, with debris clouds streaming in from robust convection to our west helping to further hamper destabilization. Still could hear some thunder, but it should be isolated. Better chances for storms and any severe weather will be to our south this afternoon ahead of the front, especially from Arkansas into west TN/MS/AL. Highs this afternoon will be around 80. Tonight high pressure will build from the Prairie Provinces into the upper Mississippi Valley, ridging southward to the Ozarks. This will provide the Ohio Valley with clearing skies and a light northwest breeze. The air mass should be dry enough to prevent much fog from forming, though there could still be some sheltered river valley fog by dawn. Lows will generally be in the lower and middle 50s, 4 to 8 degrees cooler than normal, though HREF grand ensemble (HRRR/HRW/NAM) indicates a 10-20% chance of briefly dipping into the upper 40s in rural, low-lying parts of southern Indiana. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 305 AM EDT Sun Jun 9 2024 The extended forecast period will feature quite a bit of change across the Ohio and Tennessee valleys as the pattern across the central and eastern CONUS transitions from one favoring mild and dry weather to a more typical hot summertime regime. Model guidance is fairly consistent in the pattern evolution through much of the upcoming week, with some discrepancies noted in the finer details. On Monday, an abnormally amplified pattern for mid June will be present across much of North America, with deep troughing extending from SE Canada down into the eastern US. A mid-level shortwave disturbance will swing through the Ohio Valley during the daytime hours, although it should bring little more than extra cloud cover for the afternoon hours. This cloud cover, combined with cool N/NW flow, should keep temperatures below normal on Monday. Ensemble confidence in below normal temperatures Monday afternoon is relatively good, as indicated by the ECMWF MaxT EFI, which is around -0.7 in our region. Below normal temperatures are expected to continue into Monday night and Tuesday, with EFI values continuing to indicate medium to high confidence in below normal temperatures. In addition to below normal temps, there is also high confidence in anomalously dry air Monday night into Tuesday. The NAEFS and EPS mean PWAT values are both below the 5th percentile of model climo, with ensemble mean values around 0.50" Tuesday morning. The combination of cool and dry air should help temperatures fall into the low-to-mid 50s in most locations Tuesday morning, with a few upper 40s possible in the typical cool spots. Late Tuesday into Wednesday will be the transition period as troughing lifts into the North Atlantic and positive height anomalies over the desert southwest begin to spread eastward. Sfc high pressure will remain close to the region, with continued dry air overhead and subsidence aloft negating precipitation chances. By Thursday, ensemble mean 850 mb temperatures are progged to be around 15 degrees warmer than on Monday, with warmer temperatures aloft translating down to the surface as many locations across central KY and southern IN approach 90 degrees for highs. Dewpoints and PWAT values should still be fairly modest (Td low-to-mid 60s), so while temperatures will be hot, it will be more akin to an oven than a sauna, keeping expected heat indices in check. An upper level wave is expected to slide through the upper Great Lakes and the northeast US during the late week, with an associated sfc cold front washing up near the Ohio Valley Friday into Saturday. While this could provide a trigger for showers and storms, moisture and kinematics look to be lacking at this time, so we`ll keep PoPs largely dry. The hot pattern looks to continue into next weekend, though we`ll have to keep an eye to the Gulf of Mexico as some long range guidance brings tropical moisture into our area during the June 16th-18th time frame. && .AVIATION /06Z TAFS THROUGH 12Z MONDAY/... Issued at 648 AM EDT Sun Jun 9 2024 At 11Z a cold front had crossed the Ohio River and was located roughly from LEX to OWB. This front will push south across central Kentucky this morning with scattered showers and a few thunderstorms along and ahead of it, primarily affecting BWG. A broken deck of MVFR ceilings formed earlier over southern parts of Illinois and Indiana and will spread southward through the terminals this morning before returning to VFR heights. The front will pass through BWG by early afternoon on its way into Tennessee, pushing convection to our south. Skies will gradually clear from north to south this afternoon and evening, with high pressure over the northern Plains giving us light breezes tonight under mostly clear skies. Though some valley fog will be possible by dawn, dry air moving in should prevent widespread fog. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...RAS SHORT TERM...13 LONG TERM...CSG AVIATION...13