Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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243 FXUS63 KLMK 201726 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 126 PM EDT Fri Sep 20 2024 .KEY MESSAGES... * Mainly dry and hot weather through Sunday with highs each day near or above 90 degrees. Patchy fog possible this morning. * Outside chance (20 percent) for showers and storms this evening for southern Indiana and the Ohio River vicinity. && .UPDATE... Issued at 949 AM EDT Fri Sep 20 2024 Monitoring an area of showers and storms over central Illinois that has persisted so far this morning. These have occurred within a NNE/SSW-oriented band of relatively higher precipitable waters, per latest GOES Sounder data. Peak values are roughly 1.5-1.6". Various model PW values match GOES Sounder data well with their initializations. KILX 12Z sounding showed a PW a little above that at 1.75". Most of the hi-res models have those cells diminishing in the next hour or two and latest LightningCast projections are coming down as well. That PW band should push into southern IN later this afternoon and evening...getting oriented more along the OH River Valley. Several of the CAM`s are pegging some afternoon redevelopment in central or northern IN, thanks to that increased moisture as well as with better instability. General flow aloft should allow any storms that form to push south/southeastward. Big question mark is whether they survive into our forecast area. PW`s over us now are in the 1-1.2" range. As that band drops south, PW will increase here...but there may not be enough overlap with heating/instability and drying PW`s as the cells head down here. Still feel like there`s enough of a chance to warrant raising pops into the "noticeable" range (that is, above 15%)...but will cap at slight chance (15-24%) for late this afternoon in our northern row of counties in southern IN and then later in the evening hours along and north of the Ohio River. Until then however, we`ll look at another hot day. Heat indices will stay "cool"er given dry dewpoints in the area this afternoon. Still worth staying hydrated for any outdoor events/activities. && .SHORT TERM /THROUGH TONIGHT/... Issued at 311 AM EDT Fri Sep 20 2024 Upper ridge axis from Texas to Lake Huron remains in control of our weather, so look for another dry and hot day. Low-level thickness progs suggest max temps close to persistence, perhaps a degree warmer than Thursday. Even with dewpoints remaining low enough to keep heat index values in line with the actual air temperature, most locations will reach the lower 90s, which is well above normal for this time of year. Light return flow and even the start of some moisture pooling over southern Indiana tonight will continue the warming trend for nighttime temps, with Saturday morning lows closer to midsummer normals for most. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Issued at 311 AM EDT Fri Sep 20 2024 ===== Saturday - Sunday Night ===== A weak frontal boundary will be stretching across the region Saturday morning, which could bring a few sprinkles or very light showers to some portions of the region. Overall moisture associated with the boundary will be lacking, so we certainly won`t get any relief from the dry or drought conditions from Saturday`s sfc boundary. Best chances for any light precip will be mainly north of the Western Kentucky/Bluegrass Pkwys, but chances will remain below 15% for now. Otherwise, hot and mostly dry conditions will remain for the weekend, largely thanks to strong upper ridging extending across much of the central US. Majority of our forecast area remains in a D1 Moderate Drought, though the latest US Drought Monitor (updated yesterday) expanded D2 Severe Drought conditions as well. Temperatures for Saturday will once again be in the upper 80s and low 90s. However, sfc dewpoints will mainly be in the 60s, which will help keep heat indices from creeping into the triple digits. The warm conditions continue for Saturday night as well, with above normal temperatures expected for most areas. Generally expecting 60s overnight, though temps will be on the cooler side along and east of I-75. An upper shortwave over the western US will be pivoting into the Central US on Sunday, which will help motivate the upper ridge to eventually push east. The upper ridge axis should eventually slide east of our area sometime on Sunday, which will open the door for temperatures to finally cool down, but also bring rain chances back into the forecast. PoPs will begin to filter in from the NW on Sunday, ahead of the upper wave and an associated sfc cold front. Some isolated to scattered showers and storms will be possible on Sunday, mainly for our northwestern half of the CWA, as outlined in the SPC Day 3. Sunday will also be the last day for any chance of 90 degree temperatures for the next several days. With increasing clouds and rain chances greatest across southern Indiana, they could end up remaining in the 80s, with warmer temperatures to the south and east. ===== Monday - Thursday ===== The upper ridge will continue to slide to the east for the first half of next week. Rain chances really ramp up for the Monday- Tuesday time frame as a sfc low and associated cold front pass through the area. Certainly appears to be a good chance for scattered showers and storms for at least those two days, and lingering lower chances for the mid-week as the front takes it`s time progressing eastward. We`ll definitely take any rain chances we can get at this point. Temperatures will also be quite lower for next week, with highs still in the 80s for Monday as we should still be pre-frontal, but upper 70s and low 80s for Tuesday through the end of the week. && .AVIATION /18Z TAFS THROUGH 00Z SUNDAY/... Issued at 125 PM EDT Fri Sep 20 2024 VFR conditions expected through the valid TAF period. Winds this afternoon generally are from the WSW. These should weaken this evening. Will have to watch for any storms that develop over central and northern IN this afternoon, to see if they can survive down to the I-64 corridor terminals this evening. Did not include in this forecast package given low confidence. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Air Quality Alert until midnight EDT tonight for KYZ029>031. IN...Air Quality Alert until midnight EDT tonight for INZ077>079- 090>092. && $$ UPDATE...RJS SHORT TERM...RAS LONG TERM...CJP AVIATION...RJS