Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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191 FXUS63 KLMK 211752 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 152 PM EDT Sat Sep 21 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Above normal temperatures continue, with upper 80s and low 90s for today. * Slight chance (20-30 percent) for spotty showers and storms this morning and early afternoon for central Kentucky as a weak frontal boundary stalls over the region. * More widespread precipitation chances arrive early next week ahead of a cold front. && .SHORT TERM /THROUGH TONIGHT/... Issued at 341 AM EDT Sat Sep 21 2024 The weak cold front remains north of the Ohio River this morning, and is still expected to become stationary today as it struggles to push south of the river. Ahead (south) of the front, a warm and humid airmass is in place across Kentucky, with some areas still in the mid 70s early this morning. PWATs are greatest along the front, with 1.5-1.7 inches generally west of I-65 and nosing up into central Indiana this morning. This frontal boundary, combined with an increase in low level moisture convergence, with be responsible for some isolated to scattered showers and storms this morning that could possibly linger into the early afternoon to our south. Considering the drought conditions we are experiencing, we definitely could use a good widespread soaking. However, precip coverage today will be very spotty, and not everyone will get rain. The focus for PoPs this morning will generally be along and south of the Ohio River, with around a 20-30% chance that will shift south through the Commonwealth during the entire morning hours. A few sporadic cells are already beginning to pop up on radar, and we expect this trend to continue as the front provides forcing in the warm and saturated environment. Morning ACARS out of SDF do show quite a bit of instability, with MLCAPE values exceeding 1000 J/kg, though a healthy nocturnal inversion will keep as stable at the sfc for several more hours. Model soundings for later this morning continue the trend of tall and skinny CAPE profiles, with weak shear but high PWATs. After sunrise, we`ll continue to see spotty showers, possibly with some heavy rain rates, and occasional thunder. PoPs will be limited to 20-30% today, and will have the axis of precip chances slide south of the Western Kentucky/Bluegrass Pkwys by the early afternoon. Chances will fall off by late afternoon as our low level moisture fades, leading to a dry forecast for all by this evening. Since the front will likely be hung up along the Ohio River vicinity, most of our area will remain in the warm sector. Across Kentucky, expect sfc winds to generally be from the southwest. While cloud coverage remains a big question for today, the WAA regime should still allow for sfc temps to warm above climate normals again. Still expecting upper 80s and lower 90s, though sfc dewpoints in the lower 70s will lead to heat indices being slightly warmer today, with upper 90s possible. Mostly dry weather will remain for tonight, but another cold front will be approaching the region from the west. This boundary will bring another round of rain chances, with PoPs returning to our southern Indiana counties before sunrise tomorrow. However, the best chances will eventually come in the Long Term period. Should be another mild night, with temps ranging in the 60s. Cooler temps in the east will be possible thanks to less cloud cover. && .LONG TERM /SUNDAY THROUGH FRIDAY/... Issued at 341 AM EDT Sat Sep 21 2024 Sunday - Tuesday... A more active, unsettled stretch of weather will bring some welcome relief from the heat early next week. While Sunday may start off dry, we should have quite a bit of upstream convection ongoing across portions of MO, IL, and IN. A deepening low pressure system wraps northeast toward Hudson Bay, with a long trailing cold front slowing and eventually stalling as it sinks toward the Ohio Valley. The deepest moisture and strongest lift will remain off to our northwest Sunday, along with the sfc cold front itself. However, low- level moisture will be plentiful and our proximity to more favorable dynamics just off to the northwest should allow scattered showers and isolated storms to spill over into portions of southern IN and central KY. Convective organization and maintenance will be limited by weak flow aloft, and the severe weather threat is low. Highs Sunday are somewhat dependent on convection and associated cloud cover. In general, highs should range from the low/mid 80s in southern IN to the upper 80s/near 90 in south-central KY and the Bluegrass. Early next week, an upper level shortwave trough kicks east- northeast out of the central Plains and moves over the Midwest. This wave is likely to interact with the stalled baroclinic zone, potentially bringing the Ohio Valley multiple waves of showers/storms. Much of this rain is likely to fall Sunday night through Tue/Tue night, with southern IN and northern portions of central KY currently expected to see the most. This rain could make meaningful progress toward alleviating drought conditions in some areas. Some stronger storms will be possible Monday into Tuesday. The approaching mid-level wave will provide moderately strong westerly to southwesterly flow aloft, allowing for better convective organization. Rich low-level moisture will remain in place along and south of the sfc boundary. Increased cloud cover may act to suppress sfc heating and destabilization at times, resulting in some uncertainty regarding the severe weather risk at this time range. Wednesday - Friday... Forecast confidence drops off considerably beyond Tuesday. Ensemble cluster analysis reveals multiple competing solutions with relatively equal membership for the mid to late week time frame. Unfortunately, very few conclusions can be drawn regarding the sensible weather details for this time frame. Amplified upper level flow over the United States will likely impact the strength and track of a tropical system churning slowly north through the Gulf of Mexico. Exactly what that interaction looks like will become more clear as additional model data comes in. && .AVIATION /18Z TAFS THROUGH 00Z MONDAY/... Issued at 152 PM EDT Sat Sep 21 2024 Showers and a few storms have pushed south and east of the TAF sites this afternoon. Outside of a chance for a few isolated pop ups this evening, things should be pretty quiet. Look for some mid and high clouds with a light WSW wind through sunset. Thereafter, look for light to calm winds, with perhaps some fog concerns at BWG/LEX/RGA if upper sky cover isn`t too prominent. Hinted at the best fog chance for BWG tonight. Tomorrow another disturbance crosses through our area with some afternoon showers and storms possible, mostly notably at HNB or SDF. Have Prob30s to handle that for now. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...CJP LONG TERM...EBW AVIATION...BJS