FXUS63 KLOT 032324 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 624 PM CDT Tue Aug 3 2021 .SHORT TERM... 300 PM CDT Through Wednesday night... Quiet conditions continue through the short term period with surface high pressure remaining overhead. Temperatures warmed into the lower 80s across the area today and have since hovered in the upper 70s to lower 80s under passing fair weather cumulus. A weak lake breeze did push inland but has not resulted in a noteworthy temperature drop behind it. A subtle boundary in southern Wisconsin has a couple light showers/sprinkles that developed along it that may try to dip into northern Illinois but the most likely scenario is we remain dry from this with a subsident airmass still in place. Further north a weak wave is moving south across central Wisconsin that has a couple more persistent showers that have developed. As the wave approaches and moves across the area, model guidance continues to dissipate this activity into Illinois. Similar conditions can be expected tomorrow, perhaps a tad warmer with highs in the lower to mid 80s. Can't rule out a few sprinkles tomorrow, especially along the weak lake breeze boundary but continued subsidence aloft will act against this. Petr && .LONG TERM... 225 PM CDT Thursday through Tuesday... The high pressure will move southeast of the area by the start of the forecast period, with return flow starting to pump warm, moist air into our region. This will cause a warming trend persisting into early next week as highs will be into the 80s by the end of the work week, near 90 over the weekend, and likely lower 90s by early next week. This, coupled with dewpoints rising into at least the 70s by next week, will cause heat indices in the 90s over the weekend and near to over 100 next week. With these increasingly humid conditions comes higher thunderstorm chances due to multiple upper level waves. The first of these will slowly pass through Thursday night into Friday bringing a decent chance for scattered showers and storms. Another wave will go through Sunday leading to a more active pattern for early next week. Periods of showers and storms are possible day to day early next week, some of which could be organized and strong given the forecast pattern and magnitude of instability. Slover/Warner/MTF && .AVIATION... For the 00Z TAFs... Aviation Forecast Concerns: * Easterly winds with midday/early afternoon lake breeze passage at ORD and MDW again Wednesday. Late afternoon surface analysis continues to depict weak high pressure ridge stretching west-east across IA-northern IL and northern IN. Weak gradient in the vicinity of the ridge axis continues to provide mainly light/variable winds across the region, interrupted only by the daily lake breeze circulation off of Lake Michigan. Even the lake breeze has been relatively weak with lake waters now in the low-mid 70s. East-southeast winds at ORD and MDW will diminish and become more firmly southeast this evening once again, before becoming light and variable or just calm tonight. Spotty showers and an isolated thunderstorm or two have been observed across parts of WI this afternoon, in association with a mid-level disturbance dropping south across the region. This wave will move south across northern IL later this evening, though at a diurnally less-favorable time with the loss of instability toward and after sunset. Wednesday looks to be quite similar to today, with VFR cumulus field developing by late morning and largely light/variable winds giving way to easterly lake breeze winds at ORD and MDW by early afternoon. Can't completely rule out a brief sprinkle during the afternoon along/west of the lake breeze boundary, though coverage is expected to be far too low to include in TAFs. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSChicago www.twitter.com/NWSChicago www.youtube.com/NWSChicago