Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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435 FXUS63 KDTX 082237 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 637 PM EDT Sat Jun 8 2024 .KEY MESSAGES... - Light rain will affect Southeast Michigan this evening. - A stray shower is possible on Sunday afternoon as a weak cold front crosses bringing slightly below normal temperatures by Monday. - Cool and mainly dry conditions for the first half of the week are followed by a warming trend back into the mid to upper 80s by latter half of the week. && .AVIATION... A passing mid level short wave and low level frontal boundary within a narrow ribbon of moisture transport has supported widespread light rain across Central Lower Michigan this afternoon. Over the last couple hours, the larger scale forcing and areas of light rain have been expanding across the remainder of Southeast Michigan. This forcing will persist through early this evening. There will then be an abrupt end to the rain from northwest to southeast across Southeast Michigan in the 02Z to 05Z time period as the elevated frontal forcing exits to the southeast. Ongoing shallow low level cold air advection behind the surface front is rapidly cooling the low levels. There has been some degree of support from area surface observations which suggest some areas of MVFR (perhaps some brief intervals of IFR) ceilings developing/expanding across Se Mi this evening. The bulk of current model solutions indicate a clearing of any low clouds as the rain departs to the southeast. Cold air advection within an increasing west-northwest gradient and deepening afternoon mixing depths will support an increase in winds by Sunday afternoon. Peak gusts in the 25 to 30 knot range looks reasonable based on model soundings. For DTW/D21 Convection...A lack of instability across Se Mi this evening will inhibit thunderstorms within the area of rain now expanding across metro airspace. DTW THRESHOLD PROBABILITIES... * Moderate for ceilings aob 5000 feet this evening. && .PREV DISCUSSION... Issued at 304 PM EDT Sat Jun 8 2024 DISCUSSION... Area of showers continues to fill-in from north to south this afternoon as local height falls ensue due to a broad upper low crossing Ontario. The main jet axis aloft supporting the shortwave feature extends across most of the northern tier of CONUS today while a speed max emerges over the Upper Midwest and elongates across southern Lower Michigan. Region of peak ThetaE advection arrives after 22Z this evening along the leading edge of an elevated warm frontal boundary. This boundary makes minimal northward progress, but should offer enhancements to saturation via isentropic ascent along the frontal surface. Overall, expect rather benign rainfall rates with shower activity tonight given prior dryness marked by the 08.12Z KDTX RAOB which sampled a PWAT of 0.75 inches. SPC Mesoanalysis suggests the core of the moisture plume (+1.00 inch PWATs) has already advected into western Lower with HREF supporting an eastward progression/fold this evening. A survey of instability based on several deterministic sources and representative forecast soundings highlight positive CAPE values remaining just south of the IN/OH/MI border, therefore will continue to advertise a thunderless forecast. Made minor adjustments to PoPs to slow the arrival of showers along/south of I-94 and accelerated the phase-out of PoPs upon departure of the wave after midnight. The aforementioned upper low dislodges thanks to the amplification of a ridge axis over north-central Canada which merges with a higher amplitude ridge over The West. This drives additional CVA through the Great Lakes Sunday while an area of surface troughing emerges. Westerly gradient flow strengthens after 16Z while a mixed-layer lifts to 5 kft AGL, intersecting a modest low-level wind field of 30+ knots. Breezy conditions are likely as peak gusts approach 30 mph once a weak cold front drops through and veers winds northwesterly. Can`t completely rule out a few spotty afternoon/evening showers, but moisture quality is rather meager, thus any isolated shower activity should be rather light in character. A cooler airmass settles in Sunday night with lows dipping below 50F for some areas in spite of lingering cloudiness. Also can`t rule out a few sprinkles along the shores of southern Lake Huron given the brief lake-influence setup. Sprawling high pressure spills across the Upper Midwest Monday and Tuesday offering high-confidence in a dry forecast. Air parcel trajectories tracing back into northern Canada maintain cooler-than- normal conditions Monday followed by a shift to a return-flow setup by Tuesday afternoon which marks the initiation of a warming trend through the remainder of the week. Highs break into the 80s by Tuesday with medium-range solutions (GEM/ECMWF) supporting the potential for MaxTs to approach 90F for Metro Detroit by Thursday as 850 mb temps approach 19C. A cold front and the chance for storms increases Thursday night into Friday. MARINE... Widespread showers continue over the region this evening before shifting towards the southern Great Lakes overnight as weak low pressure slides across the region. Drier conditions generally redevelop daytime Sunday with only isolated to scattered showers possible mainly over the northern half of Lake Huron tied to lingering, deepening low pressure over Quebec. This low tightens the local gradient resulting in an uptick of northwesterly winds latter half of the day Sunday into Sunday night. Overall, 20-25kt gusts expected over the region though areas for greater achievement pushing towards 30kts are the Saginaw Bay (due to the warmer waters) as well as northern Lake Huron given the favorable fetch. Lighter winds, at or below 20kts, then arrive daytime Monday as high pressure builds overhead. This high remains in place for the first of half of the work week. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....SC DISCUSSION...KGK MARINE.......KDK You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.