Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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874 FXUS63 KLOT 150507 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1207 AM CDT Sat Jun 15 2024 .KEY MESSAGES... - Relatively quiet conditions will continue tonight through Saturday night. - Hot conditions are expected Sunday through at least the middle of next week with daily highs in the 90s and overnight lows in the 70s. - Daily chances for thunderstorms will return next week, though coverage is expected to be isolated to scattered at best. && .DISCUSSION... Issued at 243 PM CDT Fri Jun 14 2024 Through Saturday night: A 1020mb surface high pressure system centered over Lake Superior is leading to quiet conditions across the Great Lakes. A lake-enhanced cold front continues to push through northeastern Illinois and will cause temperatures to fall from the mid to upper 80s to the mid to upper 70s. Meanwhile, a bank of dense fog and very low clouds is traveling southward along the Illinois Lake Michigan shoreline, and will reach the northwestern Indiana within the hour. (It should dissipate within the next few hours). Tonight looks quiet. A renewed push of winds over Lake Michigan may cause waves to quickly build to 2-4 or even locally 5 feet, but felt it would be best to maintain a "Moderate" swim risk given overnight timing. Otherwise, clear skies and overnight lows in the mid 50s are expected. Tomorrow looks similar to today with highs in the low to mid 80s. With the surface high translating further eastward into Ontario, our surface winds will turn southeasterly and keep shoreline locations cooler and in the low to mid 70s. Tomorrow night, an upper-level shortwave will lift across Iowa and into southern Wisconsin. A few showers or even a thunderstorm may attempt to develop across northwestern Illinois overnight, warranting slight chance (20%) PoPs. Otherwise, it looks like another relatively quiet, though warmer, night with overnight lows in the mid 60s. Borchardt Sunday through Friday: The big story of the next week or so is the heat and humidity that is expected to build into the area as a broad ridge and surface high set up across the eastern US. On Sunday, the ridge axis will pass overhead setting up southwesterly flow. A shortwave is expected to lift across the backside of the ridge and over the area. The jury is still out on whether the showers and storms associated with this wave will impact the CWA. Dry air in the low-levels should inhibit any showers/storms from developing. Most model guidance keeps us dry on Sunday with showers/storms moving to the north of the area, with the notable exception of the GFS. Due to this being a few days out yet and the possibility of things to change, have left slight chance PoPs for now. Model guidance is in good agreement with the placement of the ridge and high pressure with the core setting up in the Mid-Atlantic before slowly drifting north into the Northeast. With the progression, we will be on the backside gradient of the ridge, putting us in play for several shortwave disturbances through the week. Have gone with slight chance PoPs for almost every day next week to account for this. Despite the shortwave moving across the region, Sunday will be the first day of what looks to be an extended period of seasonably warm temperatures, however, there are discrepancies between the models as to how hot it will truly be. The GFS seems to be buying more into the train of shortwaves with higher dew points (70+ degrees), lower temperatures (85-90 degrees), and more widespread convection through the entire week. On the other end of the spectrum, the ECMWF and Canadian mix dew points out resulting in higher temperatures (95-100 degrees) and dry conditions. Despite the wide variety of temperatures spit out by the models, the accompanying differences in dew points result in similar heat indices (95-100 degrees). Monday is expected to be the hottest day with heat indices approaching or potentially surpassing 100 degrees areawide. At this point it does not appear that a heat advisory will be needed, however with overnight lows only cooling into the mid-70s Sunday night through Tuesday night conditions will be rather unpleasant. Conditions will be hot and humid through the remainder of the work week though not as hot as Monday as the ridge begins to break down and push off to the east. Carothers && .AVIATION /06Z TAFS THROUGH 12Z SUNDAY/... Issued at 1207 AM CDT Sat Jun 15 2024 VFR conditions are expected with no significant aviation weather concerns. Variable/light NW winds overnight will become SE just after daybreak. Small potential winds veer 180-190 infrequently at ORD/MDW in the afternoon, but winds are expected to remain largely east-of-south. Carlaw && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago