Area Forecast Discussion
Issued by NWS Chicago, IL
Issued by NWS Chicago, IL
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145 FXUS63 KLOT 061144 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 644 AM CDT Thu Jun 6 2024 .KEY MESSAGES... - Strong westerly winds today, with gusts 30-40 mph by this afternoon. Breezy again Friday with gusts 25-30 mph. - Shower chances Saturday and again in the middle of next week, otherwise mainly dry with slightly below average temps in the 70s. && .DISCUSSION... Issued at 324 AM CDT Thu Jun 6 2024 Through Friday: Early morning GOES vapor imagery displays a relatively stout mid- level short wave translating east-southeast into the western Great Lakes region, along the southern periphery of an anomalously deep (for early June) upper trough/low to our north. At the surface, this wave is mainly evident as a trough/weak secondary cold front stretching from north-central WI, southwest to near Kansas City. A band of mainly mid-level clouds was noted ahead of the surface front, along with a few spotty showers which will move east of the area along with the surface trough through sunrise. Behind the front, forecast soundings indicate a dry column and strong west- northwesterly wind profiles, which will make for strong and gusty westerly surface winds for us as mixing deepens this morning, with gusts 30-40 mph likely by midday/early afternoon. Steep low-level lapse rates and deep boundary layer mixing up through around 750 mb during the afternoon will likely produce a high-based (~7000 feet) stratocu layer, which will be more extensive and deeper northward into WI where colder mid-level temps will reside within the upper trough. Can`t completely rule out a few afternoon sprinkles near the IL/WI state line, though most areas are expected to remain dry and have maintained a dry forecast for all except for some slight chance pops far northeast Lake County IL. The deep mixing should allow temps to warm into the mid to upper 70s (coolest north) this afternoon. Winds will ease toward sunset with the loss of stronger diurnal mixing, but will remain breezy through the evening. Overnight lows will dip into the 50s area-wide, with another breezy (gusts 25-30 mph) day Friday with highs in the mid- 70s in most locations. Friday night through Wednesday: Other than brief shower/thunderstorm chances Saturday and again Tuesday or Wednesday, the majority of the period looks dry with temperatures generally slightly cooler than average (70s). There is some indication in extended ensemble guidance that we`ll warm back into the 80s for daytime highs at or just beyond the end of the current forecast period. The upper low to our north will drift slowly east across the Lakes to New England through Saturday, while an elongated upper trough trails back west through the Canadian Prairie Provinces. Guidance is in decent agreement with developing another amplifying mid-level jet/vort max along the southern periphery of the upper trough and tracking it across the upper Midwest and western Great Lakes Saturday, with another accompanying surface cold front. This presents another chance for at least scattered showers and perhaps a few isolated thunderstorms for the forecast area during the day, though some guidance is probably overdone on QPF amounts and coverage as return moisture looks to be initially blocked by high pressure across the western Gulf. Dry weather then looks to return Sunday into Monday as global ensembles depict a deepening upper trough across the east with seasonably cool surface high pressure expanding across the upper Great Lakes. A more progressive, zonal pattern is forecast by mid-week, though with guidance depicting another short wave propagating through the flow across the upper Midwest with another cold frontal passage and associated shower/thunderstorm chances. Some timing differences remain amongst the global guidance/ensembles, and NBM pops are currently spread out across Tuesday and Wednesday. No changes made to these low chance pops at this distance, though would expect one of these days may be largely dry once models come into better agreement with the timing of the front. Ratzer && .AVIATION /12Z TAFS THROUGH 18Z FRIDAY/... Issued at 639 AM CDT Thu Jun 6 2024 The primary forecast element of note continues to be increasing wind speeds through the day, with gusts over 30 kts by mid- afternoon. The direction should remain from the west to northwest. Speeds will then gradually diminish during the evening. Friday will also be breezy but not quite as strong as today, with gusts more likely to remain mostly below 30 kts. Lenning && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Small Craft Advisory until 10 PM CDT this evening for Winthrop Harbor IL to Gary IN. Small Craft Advisory from 1 PM this afternoon to 10 PM CDT this evening for Gary to Burns Harbor IN-Burns Harbor to Michigan City IN. && $$ Visit us at weather.gov/chicago