Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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878 FXUS63 KLOT 100533 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 1233 AM CDT Mon Jun 10 2024 .KEY MESSAGES... - Dangerous swimming conditions will continue at Lake Michigan beaches today. - Tuesday through the end of the week will feature increasing temperatures and chances for showers and thunderstorms, with the latter particularly on Thursday and Friday. - After a brief respite on Saturday, summer-like temperatures are poised to return early next week. && .DISCUSSION... Issued at 233 PM CDT Sun Jun 9 2024 Through Monday night: A mid-level trough and associated surface trough/front will shift S/SSE across the forecast area this evening into the early overnight hours. A wind shift from WNW to NE with gusts to 20 knots is expected along the Lake Michigan shore early to mid- evening and will result in deteriorating swimming conditions. A Beach Hazard Statement remains in effect beginning 9pm this evening for the entire Lake Michigan shore in IL and IN, with the potential for dangerous swimming conditions to begin as early as 8pm if the front exhibits a quicker forward motion over the next several hours. A secondary wind push late this evening with gusts of 25 knots or higher will generate continued dangerous swimming conditions through the day Monday. A mixed nocturnal PBL owing to modest CAA overnight may allow the post frontal stratus to grow sufficiently deep to squeeze out some sprinkles or patches of drizzle. This is particularly the case near the lake where added lake moisture from a long fetch will counteract overall synoptic dry air advection. Have opted to include slight chance sprinkles roughly around the lake-adjacent counties late this evening through sunrise Monday. Otherwise, diurnal heating and continued dry advection should erode the stratus or lift and scatter the stratus into shallow cumulus from north to south through the morning Monday. Max temps will be well below normal for early/mid June, with highs ranging from the low 60s along the shore to the low 70s well inland. Mostly clear skies and a passing ridge Monday night will yield a chilly night with lows in the mid to upper 40s inland to the low 50s in the core of the Chicago metro. Kluber Tuesday through Sunday: Next week, a quintessential summertime ridge is expected to develop across the west-central United States leading to quasi- zonal to northwesterly upper-level flow across the Great Lakes. The result locally will be gradually warming temperatures Tuesday through the rest of the workweek. Highs on Tuesday in the upper 70s will warm to the mid to upper 80s by Thursday, with overnight lows climbing into the low to mid 60s. Chances for precipitation will be tied to upper-level shortwaves embedded in the flow aloft. The first wave will swing through the Great Lakes in the Tuesday night into Wednesday morning timeframe, though low-level moisture return ahead of the wave looks rather limited. As a result, only a few scattered non-soaking showers are our expectation, warranting low-end (15-20%) PoPs. The next wave (or series of waves) will move through the general region in the Wednesday night to Friday timeframes. With plenty of upper-level shear (thanks to the proximity of the upper-level jet focused to our north) and moisture-laden instability, the pattern will be supportive of episodic mesoscale convective systems (MCSs) with gusty to damaging winds and soaking downpours. Pinpointing the times and locations of summertime MCSs is a futile effort more than 48 hours out, so for now, will carry mid-range chance (30-40%) PoPs centered on Thursday in favor of refinements in the coming days. It`s worth noting temperatures Thursday and Friday will depend on the cadence of convective episodes, any debris upper- level cloud cover, and the eventual placement of an effective (outflow-reinforced) front. By Saturday, any effective front reinforced by episodic convective episodes should slip south of our area leading to onshore flow and a modest break in seasonably warm temperatures. Highs should range from the lower 70s lakeside to the low to mid 80s inland. Thereafter, ensemble guidance supports the development of pronounced troughing across the western US and ridging over the Great Lakes, which should lead to a return of summer-like warmth (as well as humidity) at some point early next week. Borchardt && .AVIATION /06Z TAFS THROUGH 12Z TUESDAY/... Issued at 1233 AM CDT Mon Jun 10 2024 Key Messages: - MVFR CIGS overnight with potential for brief period of -DZ and associated MVFR VSBYS and IFR CIGS at ORD/MDW/GYY 1500-2000ft MVFR stratus has overspread ORD and MDW already this hour and may get close to DPA. Further upstream near Milwaukee, drizzle has been observed with IFR ceilings near 900ft with visibility also dropping to the 2-4 SM range. To account for this potential, trended down the inherited TEMPO groups to include -DZ and 5SM visibility reductions in addition to IFR ceilings during the roughly 7-11Z timeframe. Confidence in this maintaining itself into Illinois is not especially high but felt it was prudent to mention the potential in the TAFs. Will continue to monitor over the next few hours. Winds will remain steady out of the northeast across the Chicago area terminals overnight and generally northerly toward RFD. Directions could return to a prevailing northerly direction after daybreak for all terminals but it may vary between 340-020 at times before returning to a prevailing northeast to easterly direction with an eventual lake breeze passage early afternoon. Winds become light and variable after sunset. Petr && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Beach Hazards Statement through late tonight for ILZ006-ILZ103- ILZ104. IN...Beach Hazards Statement through late tonight for INZ001-INZ002. LM...Small Craft Advisory until 9 PM CDT this evening for the IL and IN nearshore waters. && $$ Visit us at weather.gov/chicago