Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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773 FXUS63 KLMK 251047 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 647 AM EDT Wed Sep 25 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Scattered showers and storms linger today and tonight, mainly across southern and eastern KY. No severe weather expected. * Widespread moderate to heavy rain and windy conditions on Friday as the remnants of Tropical Storm Helene move through the Lower Ohio Valley. && .SHORT TERM /THROUGH TONIGHT/... Issued at 334 AM EDT Wed Sep 25 2024 Some convective activity going on across the Bluegrass region at this hour as scattered convection has re-fired thanks to some lingering instability and a upper impulse positioned east of the upper trough axis. In addition, we`re seeing mix of low stratus and some fog across the area. Any fog concerns should be transient in nature given the increasing upper sky cover, however could have some patches of dense fog from now until an hour or two after sunrise. Will continue to monitor. A shortwave trough has closed off over the lower Missouri/Mid Mississippi River Valley early this morning. This closed upper low will meander just to our west today, before retrograding back to the SW just a bit by tonight. Meanwhile, the upper jet to the east of closed low will remain oriented SW to NE up the Appalachian spine, roughly parallel to the surface frontal boundary. This setup should keep the focus of most of our shower and storm chances across our southern and eastern portions of the CWA today and tonight. Overall, not as much instability to work with, and deep layer shear will be weaker compared to yesterday. So, severe weather is not anticipated. A few spots could pick up a quarter to half an inch of additional rainfall through tonight for areas along and east of a Bowling Green to Lexington KY line. NW of that line, amounts are more likely to stay at a tenth of an inch or less. Fairly small diurnal range expected for today as we sit under pretty heavy cloud cover. Highs are only expected to reach into the mid and upper 70s, with lows later tonight dropping mostly into the mid 60s. Some mid to upper 50s possible west of I-65 where some clearer skies are possible. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Issued at 334 AM EDT Wed Sep 25 2024 All eyes are on Tropical Storm Helene for the medium-range portion of the forecast. NHC still expects Helene to intensify rapidly over the next 48 hours while moving generally NNE over the eastern Gulf of Mexico. Unfortunately, Helene is forecast to strengthen into a major hurricane by its landfall Thursday evening along the FL Big Bend coast. Locally, there is a chance for mainly scattered light rain on Thursday. We really won`t feel any impacts from the tropical system until late Thursday night and Friday. We`ll see steady moisture advection as southeasterly low to mid-level winds begin to increase slightly. The upper low to our west is forecast to wobble southwest over SE Missouri and NE Arkansas. Light rain accumulations (generally less than 0.10") will be possible south of I-64, with perhaps a few spots in south-central KY seeing up to 0.10-0.20 inches. Cloud cover should be increasing quickly from east to west by Thursday morning. Afternoon highs will range from the lower 70s in the Bluegrass/Lake Cumberland regions to the mid/upper 70s west of I-65. Helene will gradually weaken after making landfall, but will race northward fairly quickly through GA Thursday night. Widespread moderate to heavy rainfall chances ramp up from south to north overnight into Friday. Northeasterly sfc winds are forecast to strengthen to around 15 kts prior to sunrise Friday. Overnight lows in the low to mid 60s should be common. Helene is forecast to then curve northwest over the Lower Ohio Valley on Friday while wrapping cyclonically around the southeastward rotating upper low (Fujiwhara effect). Widespread tropical rains and windy conditions are likely. Gusts of 30-35+ mph appear likely based on LREF data, but higher gusts are not out of the question. The severe convective risk appears to be low at this time, but confidence is low on the details until the forecast track can be further refined. Minor flooding issues will likely become more common on Friday with the arrival of tropical moisture after multiple days of unsettled/convective weather. Showery weather continues over the weekend. Post-tropical Helene merges with the remnant upper low, and the wave spins over the Lower Ohio Valley for a couple days before opening up and exiting off to the northeast early next week. Overall, 2-4+ inches of additional rainfall will be possible today through Sunday. The highest amounts are likely to occur across southern KY. This rainfall will significantly help alleviate drought conditions across the region. While higher rainfall totals and a higher flooding risk will exist across the Southeast, there may be slight risk for isolated flash flooding Friday. Long-fused significant river flooding is unlikely, as area rivers should be able to handle this rainfall. && .AVIATION /12Z TAFS THROUGH 18Z THURSDAY/... Issued at 646 AM EDT Wed Sep 25 2024 MVFR to IFR ceilings currently ongoing at HNB/LEX/RGA, with BWG/SDF staying VFR. The mix of clouds has helped keep flog mostly in check, although can`t rule out a brief vis reduction still this morning around sunrise. Surface winds will be pretty light and variable through this period given the wavering weak frontal boundary across the area. After some improvement through the morning, VFR conditions will return. Afternoon and early evening forecast brings some chances for showers or a storm to return, but will be scattered in nature. Included Prob30s for this threat. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...BJS LONG TERM...EBW AVIATION...BJS