Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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942 FXUS63 KLOT 261935 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 235 PM CDT Wed Jun 26 2024 .KEY MESSAGES... - Dangerous swimming conditions at Lake Michigan beaches into or through Thursday afternoon. - Strong to severe thunderstorms and flash flooding are possible Friday night into Saturday. && .DISCUSSION... Issued at 235 PM CDT Wed Jun 26 2024 Through Thursday Night: Following a warm and less humid afternoon behind the cold front passage, a quiet and relatively cool night is in store, especially by recent standards. Forecast lows tonight are generally in the 55-60F range outside of Chicago, and lower 60s in and near the city. A secondary surge of cold air advection, strongest down the length of Lake Michigan, will enhance northerly winds and result in building waves. The enhanced northerly winds should continue until high pressure centers over the lake tomorrow (Thursday) afternoon and causes speeds to steadily ease. As a result, high (but gradually subsiding) waves and strong currents will persist into the afternoon. With this in mind, will be extending the Beach Hazards Statement for northeast Illinois and northwest Indiana beaches through the mid afternoon hours. Aside from the dangerous swimming conditions, there are no other concerns through Thursday night. The most comfortable daytime conditions in weeks can be expected, with inland highs in the mid 70s to near 80F, upper 60s to lower 70s near the lake, and dew points in the upper (locally mid) 40s to mid 50s. Favorable radiational cooling conditions to start Thursday evening will allow for similar low temperatures to those of tonight, though increasing clouds and warm advection will result in steady or slowly rising temperatures overnight into early Friday. Castro Friday through Wednesday: A chance for showers and storms will return Friday and Saturday as multiple shortwaves propagate through the area. Convection is expected to form across the Mid and Upper Mississippi Valley on Friday and move towards the CWA through the day. Instability will be quite meager across the area with MUCAPE values below 500 J/kg resulting in decaying showers and storms reaching the area through the day on Friday. The best chances for precipitation are in the western portion in the CWA. Southerly flow on Friday will bring a plume of moisture into the area in evening leading to some elevated instability building overnight. A shortwave may provide enough lift late Friday night for elevated showers and storms to regenerate. Continued southerly flow overnight and diurnal heating will allow some modest instability to build Saturday. However, a warm nose will keep things pretty well capped despite 1000-2000 J/kg of MLCAPE. Any storms that are able to break through this cap and form have the potential to become strong to severe given the modest instability and 30-35 kts of deep layer shear bringing a threat for strong winds and hail. With PWAT values expected to be in excess of 2", these storms Friday and Saturday also pose a risk for flash flooding. High pressure will build into the region on Sunday bringing quiet weather through Monday, though seasonably cool with highs in the mid to upper 70s. An active pattern looks poised to return Tuesday, brining shower and storm chances through the middle of next week. Carothers && .AVIATION /18Z TAFS THROUGH 00Z FRIDAY/... Issued at 1226 PM CDT Wed Jun 26 2024 A cold front has been advancing southeast through the area this morning bringing scattered showers to all of the TAF sites. It is currently just south of KORD, however, some scattered showers are still hanging around on the backside of the boundary. Thus have opted for a prevailing VCSH at KORD through 19Z, KMDW through 20Z, and KGYY through 21Z. Clouds are expected to clear out behind this boundary with VFR conditions expected at all five TAF sites through the end of the TAF period. Northwest winds will shift to northeast this afternoon at KORD, KMDW, and KGYY as a lake breeze pushes inland. A shift to northwesterly winds will also occur at KDPA and KRFD later in the evening. Winds will become stronger with a few gusts possible with the northeasterly shift. Winds will remain northeasterly through the end of the TAF period though the strongest winds will be confined to areas near the shore of Lake Michigan. Carothers && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Beach Hazards Statement from 10 PM CDT this evening through Thursday morning for ILZ006-ILZ103-ILZ104. IN...Beach Hazards Statement from 10 PM CDT this evening through Thursday morning for INZ001-INZ002. LM...Small Craft Advisory from 10 PM this evening to 10 AM CDT Thursday for the IL and IN nearshore waters. && $$ Visit us at weather.gov/chicago