Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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300 FXUS63 KLOT 092327 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 627 PM CDT Sun Jun 9 2024 .KEY MESSAGES... - A cold front will arrive this evening with gusty northerly winds lasting through Monday along with building waves and dangerous swimming conditions for Lake Michigan beaches. - 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 /00Z TAFS THROUGH 06Z TUESDAY/... Issued at 625 PM CDT Sun Jun 9 2024 Aviation weather concerns are: - Incoming NE wind shift with a cold front. - Potential MVFR cigs tonight and a small chance for a few sprinkles A strong cold front is moving rapidly southward down the lake and will be delivering a NE shift at ORD, MDW, and GYY shortly, and a bit later this evening at DPA. Gusts up to 30 knots are expected near GYY and about 25 knots at ORD/MDW as the front passes. Generally VFR cigs are expected tonight although some spotty MVFR cigs may materialize overnight. A few sprinkles/showers can`t be ruled out tonight, although chances are too low for a mention in the outgoing 00z TAFs. Cigs will gradually lift tomorrow and winds will ease. At ORD/MDW, winds may oscillate between 350 and 020 through the morning before a lake breeze reinforces NE winds during the afternoon. Carlaw && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Beach Hazards Statement through late Monday night for ILZ006- ILZ103-ILZ104. IN...Beach Hazards Statement through late Monday night for INZ001- INZ002. LM...Small Craft Advisory until 9 PM CDT Monday for the IL nearshore waters. Small Craft Advisory until 9 PM CDT Monday for the IN nearshore waters. && $$ Visit us at weather.gov/chicago