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Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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871 FXUS63 KLMK 121912 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 312 PM EDT Fri Jul 12 2024 .KEY MESSAGES... * Mostly dry weather and warming temperatures expected for for the weekend. * Triple-digit heat index values could return Sunday afternoon and are likely early next week. * Shower and storm chances look to increase by the middle of next week as a frontal boundary sinks into the area. && .SHORT TERM /THROUGH SATURDAY/... Issued at 311 PM EDT Fri Jul 12 2024 A clearly defined MCV is rotating into the MO Bootheel at this hour, and will continue to trigger isolated to widely scattered convection across western KY late this afternoon into early evening. Some of that additional convection could survive into our W through around sunset. Meanwhile, isolated convection across our area has kicked off late morning into the early afternoon, with chain reaction outflow kicking off additional coverage. Overall, storms have remained relatively weak and short-lived given the lack of deep layer shear, and very poor mid level lapse rates (less than 5.5 C/KM). A few storms have gotten a bit strong mainly along and west of I-65 where lightning and gusty outflow have been noted. Expect that H6 subsidence inversion will remain in place through the evening, and given that don`t expect storms to get too strong. It is fairly unstable as ML CAPE values will likely peak in the 1500-2000 J/KG range, but again the mid level inversion, poor mid level lapse rates, and lack of stronger deep layer shear are all limiting factors. A couple of SPS statement for gusty winds to 40 mph are still possible through sunset, before we lose heating/instability. Looking for convection to die off in the evening with the loss of heating, and a relatively quiet overnight. Temps should be a bit milder than last night with lows in the upper 60s and low 70s for most. Seems like a fairly good setup for some patchy fog development overnight, and will have to assess late afternoon crossover Ts for whether we think we could have any dense fog potential. Right now, guidance likes the idea of fog, but isn`t too aggressive with dense fog. Some uncertainty with upper sky cover hurts confidence a bit in just how widespread/dense it may become. Looking for another hot, humid, and mostly dry day on Saturday. General troughiness remains over the area, but overall this will be a pretty weak mechanism for triggering. Will carry some isolated pops across western CWA first of the day, but gradually drying out through afternoon. Given less convection, expect temps to warm a degree or two from today. This puts most locations a bit more solidly into the low 90s. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 311 PM EDT Fri Jul 12 2024 Sunday - Tuesday Upper level ridging will remain to our west, with more zonal flow expected across the eastern half of the US. This pattern will promote a mostly dry forecast, with the exception of an isolated shower or storm possible for a few hours north of the Kentucky Parkways Sunday afternoon. Otherwise, hot and dry weather will be the story as sfc high pressure holds it`s position to our east. Temperatures are forecast to rise into the upper 90s each day, with Monday possibly being our hottest day of the forecast period. Dewpoints will be in the upper 60s and low 70s, which will translate to heat indices between 100-105F. Practice heat safety in the coming days by drinking plenty of water, taking breaks indoors, checking on vulnerable neighbors, and never leaving children or pets in a vehicle unattended. There will be little relief during Sunday night and Monday night, with temps expected to remain in the 70s. Monday night may even feature some mid- to upper-70s in the urban areas. By Tuesday afternoon or evening, we may begin to see PoPs return to the area ahead of an approaching cold front. The driving upper trough will remain well north, but the associated cold front will be diving southward from the upper midwest into the lower Ohio Valley. An increase in RH along with some weak mid-level forcing ahead of the front may result in some isolated precip activity late in the day, but the primary rain chances will come with the front on Wednesday. Wednesday - Friday Best shower and storm chances will be on Wednesday as the cold front passes through the region. As of now, model soundings show a marginally unstable airmass, with weak shear and mostly unidirectional flow. PWATs approaching 2 inches will support heavy rain rates, but confidence on any organization and severe potential remain low at this time. Will be something to keep an eye on in the coming days. After FROPA, PoPs will linger as the front slowly shifts to our south. Will keep PoPs going into the end of the week as well, though chances will not be as high as Wednesday. Temps should rebound to near-normal for both Thursday and Friday, with highs in the mid- to upper-80s. && .AVIATION /18Z TAFS THROUGH 00Z SUNDAY/... Issued at 157 PM EDT Fri Jul 12 2024 Looking for mostly VFR conditions through this cycle, although a couple of hazards that could briefly affect that. First off, isolated to widely scattered showers and storms have developed, and these could briefly reduce vis or create some gusty conditions. Coverage is still pretty sparse, so not enough confidence to mention any TS impacting a terminal, but will amend as necessary. The second hazard could come in the form of some fog overnight, and especially the pre-dawn hours. Have advertised MVFR vis restrictions for now, but may have to put some lower vis in with later updates in what should be a favorable fog setup. Other than that, look for generally light and erratic (t-storm outflow boundaries) surface winds this afternoon and evening, going mostly calm overnight. Sct cu around 5-6 feet are expected, along with increasing upper sky cover from convective blowoff. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...BJS LONG TERM...CJP AVIATION...BJS