990 FXUS63 KLMK 271729 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 129 PM EDT Mon Jul 27 2020 .Forecast Update... Issued at 1245 PM EDT Mon Jul 27 2020 Cu field starting to look a little more agitated over southern Indiana, and will provide our best precip chances as the afternoon progresses. Another area of deeper Cu along the KY/TN border, but in between there is enough mid-level dry air that convection will be delayed until quite late in the afternoon. Current forecast remains well on track, with timing tweaks to the hi-res products. && .Short Term...(Today and tonight) Issued at 302 AM EDT Mon Jul 27 2020 Early morning satellite imagery revealed clear to partly cloudy skies across the region. Temperatures were mainly in the lower 70s. Some patchy river valley fog is possible again this morning, but widespread fog is not anticipated at this time. Minimum temperatures should cool into the upper 60s to the lower 70s. For today, we'll start off the day with mostly sunny skies, but expect another Cu field to develop by mid-late morning. Shower and thunderstorm coverage is expected to ramp up in the afternoon as a cold front drops into the region from the northwest. Main areas of thunderstorm activity today look to be confined to southern Indiana and the northern half of Kentucky. We plan on ramping up PoPs a bit more with this forecast in the above areas. Further south, mainly along and south of the Cumberland Parkway area, the overall coverage of thunderstorms is expected to be much more scattered. In terms of strong/severe storm potential, overall environmental shear parameters look to remain pretty marginal locally. Soundings show about 20-25kts of shear with plenty of instability to work with. Main threat today with storms would be damaging wind gusts. However, given the higher PWATs, torrential rainfall will accompany any storm, along with frequent lightning. Highs for the day look to top out in the upper 80s to around 90 before the storms flare up. For tonight, convection is expected to linger into the evening hours as the front sags southward into Kentucky. However, the coverage looks to wane quite a bit after sunset as we lose instability and the boundary layer become more stable. Therefore, will keep higher PoPs in the forecast for the evening hours and then allow them to sharply decline towards midnight. Some isolated showers/storms are possible overnight with lows dropping into the upper 60s to the lower 70s. .Long Term...(Tuesday through Sunday) Issued at 235 AM EDT Mon Jul 27 2020 ...Unsettled and Cooler Week Ahead... By Tuesday morning, an expansive 5H closed low will dominate much of Ontario and the upper Great Lakes with broad troughing extending across much of the eastern third of the US. The associated surface cold front will be stalling out roughly along the OH River by this time, resulting in continued chances of showers and thunderstorms across southern Indiana and central KY. Dry air will begin to advect in from the north by Tuesday afternoon, which should limit afternoon convection across our southern Indiana counties while likely PoPs will continue for most of the Commonwealth. With modest mid-level lapse rates and meager shear, severe chances will be limited. But with PWATs around 2.00 inches and relatively steep low level lapse rates, heavy rain, locally gusty winds, and cloud to ground lightning will be the most likely hazards. Wednesday may prove to be the driest day of the long term for those roughly north of the Parkways as the surface boundary sags south across central to southern KY. Soundings show relatively dry and stable air north of the boundary (PWAT ~ 1.30", CAPE <= 1000 J/kg), while southern parts remain within a moist and unstable airmass (PWAT ~ 2.00", CAPE <= 2500 J/kg). Isolated showers and thunderstorms are still possible in the north, just less likely than across south central KY. By Thursday, a parade of shortwaves ride along the boundary bringing rounds of showers and storms to the area. One shortwave in particular looks to surge SE over the Rockies and a large upper high over the Four Corners, undergo lee-cyclogenesis, and bring widespread showers and storms to our area for the end of the week and into the weekend. Tuesday and Wednesday will remain warm and humid with highs in the mid to upper 80s. Cooler air moves in by Thursday and sticks around through the weekend with highs generally in the low 80s. && .Aviation...(18Z TAF Issuance) Issued at 115 PM EDT Mon Jul 27 2020 Timing and impact of thunderstorms will be the main challenge in this TAF set. Will run with at least a TEMPO group for HNB within an hour or two after issuance, and SDF a bit later in the afternoon. BWG will be a last-minute call as the Cu field near the KY/TN line is destablizing as well, but VCTS seems the most likely scenario there. Will delay any storms getting into LEX until quite late in the afternoon. Convection should die down just after sunset, with a mostly quiet night in store. Front will linger across the area on Tuesday, so isolated/scattered storms in play before the end of the TAF period, but won't go any more than VCTS yet. Prevailing VFR conditions are expected, as any thunderstorm restrictions will be very short-lived and difficult to time. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RAS Short Term...MJ Long Term....CG Aviation...RAS