470 FXUS63 KLMK 061747 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 147 PM EDT Wed Oct 6 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 943 AM EDT Wed Oct 6 2021 Radar showing a steady stream of showers moving northward through central KY and southern Indiana, mostly light but with some pockets of moderate rainfall. AMDAR soundings out of SDF do show some dry air below 700mb, which would account for the lack of rainfall in regional obs. There does appear to be a gap approaching the southern KY border that will result in decreased PoPs for a few hours before a diurnal uptick kicks off early this afternoon. So far, light accumulations have resulted from current showers, with KY Mesonet showing less than a tenth of an inch across most of central KY and about a half inch in the Bowling Green area of the CWA. Have adjusted PoPs to better portray the above scenario. Otherwise, current forecast remains on track. Updated products forthcoming. && .Short Term...(Today and tonight) Issued at 335 AM EDT Wed Oct 6 2021 Our weather remains under the influence of a closed upper low over northern Arkansas this morning. This low will slowly slide northward into west-central Missouri by Thursday morning. Stalled boundary currently cutting across central Kentucky will drift northward today as a warm front. Providing plenty of deep moisture across the region with PWAT values between 1.50" to 1.60" and dew points in the upper 60s to near 70. Hi-res models show a couple waves of showers and storms working from south to north throughout the day today. The first looks to be associated with a 500mb vort max that will bring occasional showers through the morning. The next wave arrives in the afternoon sparking scattered areas of showers and thunderstorms. Models soundings continue to show a nearly unidirectional southerly wind profile with just some slight veering below 500mb. Instability looks to be around 1500-2000J/kg. Low LCLs combined with modest effective SRH values around 100 M2/S2 could lead to rotating or splitting updrafts providing a marginally weak tornado threat with any afternoon storms. Cloud cover this morning and today would likely limit instability later this afternoon along with generally weak shear for most of our CWA (20-25kts). The best dynamics for any strong to potentially severe storms would be across extreme southwestern KY including the southwest corner of our CWA and most of western/central TN. That is where the Storm Prediction Center has a marginal risk of severe weather. The main threat with any storms that may develop will be heavy rain that could lead to localize flooding. strong gusty winds and as mentioned above the slight risk of an isolated spin up tornado. As the upper level closed low continues to move northward in MO, another mid level vort max will work across central KY from the south to north as a 25-35 kt LLJ develops over central and eastern KY. Going with likely PoPs across all of the CWA during the overnight hours. PWATs will remain around 1.60-1.70" so brief periods of heavy rain are once again likely. .Long Term...(Thursday through Tuesday) Issued at 307 AM EDT Wed Oct 6 2021 Slow-moving upper low will rotate NNE over St. Louis on Thursday and open up to the northeast across the Great Lakes Friday into Saturday. At least scattered showers are likely to be ongoing at 12z Thursday. A moist airmass will remain in place along with deep southerly flow on the east side of the low. Southerly low-level jetting does lift north of the region during the day, so think coverage at any one hour will generally be scattered. However, confidence is high in scattered showers and a few storms as well. So will keep 6- and 12-hr PoPs quite high. Forecast soundings suggest a weak, skinny CAPE profile which should limit the threat for severe storms. Deep layer shear will be around 25-30 kts, but low-level shear is weaker relative to Wednesday. Overall, Thursday is showery at times with highs in the mid 70s. Precip coverage likely diminishes to isolated at best Thursday night. Drier air slowly, steadily works in from the south behind the departing upper low. The upper low rotates over Milwaukee on Friday, with the lingering upper trough draped over the lower Ohio Valley. Expect a drier day in general, but diurnal heating may help spark isolated showers. Look for partly to mostly sunny skies and highs in the mid to upper 70s. Strong upper level ridging replaces the upper level trough for the weekend, and summer warmth makes a return. Heights will continue to be pumped up through Sunday, downstream of a potent upper level wave over the Southwest US. Highs in the upper 70s to lower 80s should be common Saturday, with low to mid 80s possible Sunday. Mild weather continues into early next week. The aforementioned wave of low pressure appears likely to develop northeast from the southern Plains, eventually weakening over the Midwest early next week. However, model consistency and agreement on this system isn't great thus far. Confidence is fairly low on the exact evolution of the low and its attendant cold front. There is at least a low chance for showers and storms Monday into Tuesday. && .Aviation...(18Z TAF Issuance) Issued at 145 PM EDT Wed Oct 6 2021 IMPACTS: Periods of IFR/MVFR CIG/VIS in showers and thunderstorms. Potential IFR CIGs Thursday morning. Continued periodic MVFR conditions in showers and thunderstorms for the rest of the forecast cycle. DISCUSSION: An upper low over AR/MO border continues to feed deep layer moist air over the region resulting in waves of showers and thunderstorms. Expect periods of IFR VIS and MVFR CIGs this afternoon with convective activity. Best chances of storms exists after 21Z through around 07/02Z and another shot associated with a weak 20-25kt low level jet Thursday morning. IFR CIGs will likely linger until late morning, slowly lifting to MVFR, and finally to VFR by mid to late afternoon. Scattered showers will continue Thursday with the possibility of afternoon storms. CONFIDENCE: Medium on timing and conditions. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...CG Short Term...BTN Long Term...EBW Aviation...CG