Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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196 FXUS63 KLOT 111726 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1226 PM CDT Sat May 11 2024 .KEY MESSAGES... - Dry, seasonable, and breezy conditions this weekend. - Periods of showers and a few thunderstorms are expected Sunday night through early Tuesday. There will be many dry hours. && .DISCUSSION... Issued at 319 AM CDT Sat May 11 2024 Through Sunday: A cold front continues to advance across eastern IL and northern IN this morning with an area of scattered showers traversing ahead of the boundary. These showers will continue to exit our area over the next hour or so leaving us with dry conditions for the rest of the weekend. However, the combination of cold advection in the wake of the front and a lingering pressure gradient will promote breezy northwest winds this afternoon. Gusts are expected to top out in the 20 to 30 mph range today before gusts gradually subside this evening. Despite the cold advection, temperatures will remain seasonable today with highs in the upper 60s to lower 70s though onshore flow across northwest IN will hold readings a few degrees cooler. Heading into Sunday, mid-level ridging will build into the Great Lakes which will turn winds out of the southwest and usher in warmer temperatures. Therefore, highs on Sunday are forecast to top out in the upper 70s to lower 80s. Though strong diurnal mixing is expected again on Sunday which will promote breezy winds, but this time in the 20 to 25 mph range. Additionally, the deeper mixing should also lower dew points, despite the warm-moist advection, which will make RH values dip into the 30-35 percent range Sunday afternoon. Thankfully, the recent rains and greening vegetation should limit any fire weather concerns. Yack Sunday Night through Friday: Monday into Tuesday, the cut-off low currently meandering in the southwestern United States will become "re-absorbed" into the upper- level flow while drifting eastward toward the mid Mississippi River Valley. As a result, waves of showers and a few thunderstorms are expected to roam through the general region starting as early as Sunday night and lasting through Tuesday. At this point, the Monday afternoon-Tuesday morning period is favored for the highest coverage of showers and storms locally, which may include swaths of locally heavy rainfall (>1") given relatively slow storm motions, an abundance of synoptic-scale lift, and PWATS nearing 1.4". Outside of waves of showers and thunderstorms, temperatures early next week will be like a tale of two seasons with highs in the mid 70s away from Lake Michigan on Monday and only in the low to mid 60s on Tuesday (thanks to expansive onshore flow off Lake Michigan). Wednesday and at least the first half of Thursday, a surface high pressure system and upper-level ridge will move over the Great Lakes allowing for a rebound in temperatures into the low to mid 70s. With the core of the surface high pressure system expected to pass north of our area, the surface wind will maintain an onshore component. As a result, temperatures will continue to be cooler near the Lake Michigan shoreline. Ensemble model guidance continues to favor the next opportunity for showers and a few thunderstorms to arrive sometime in the late Thursday to early Friday timeframe. A much-too-early look at the latter half of May suggests relatively seasonable weather with highs in the 70s and regular opportunities for showers and thunderstorms. (In other words, there are no signs of much above or below normal temperatures, or for much above or below normal precipitation). Borchardt && .AVIATION /18Z TAFS THROUGH 00Z MONDAY/... Issued at 1225 PM CDT Sat May 11 2024 The primary aviation weather concerns through the 18Z TAF period include: * A lake breeze shifting NW winds to easterly this afternoon/evening at the Chicago sites NW winds will continue gusting upwards of 30 kt for the remainder of the afternoon. A lake breeze just starting to protrude inland early this afternoon is expected to move across the Chicago terminals in the late afternoon/early evening abruptly shifting NW winds to easterly. This wind shift is expected to occur at MDW near 22Z and at ORD closer to 00Z. Gusts should be cut off behind the lake breeze, although sustained winds may continue to move at around 10 kt through dusk. Winds will veer to southerly near or under 5 kt for the late evening and overnight. SW winds will begin gusting into the teens during the morning, possibly as early as daybreak. More appreciable gusts into the 20-25 kt range are expected as early as mid-morning, more likely that they hold off until the afternoon. VFR can be expected throughout the period. Doom && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago