


Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI
Issued by NWS Detroit/Pontiac, MI
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404 FXUS63 KDTX 241058 AFDDTX Area Forecast Discussion National Weather Service Detroit/Pontiac MI 658 AM EDT Sat May 24 2025 .KEY MESSAGES... - A few sprinkles with perhaps a couple isolated showers over the Thumb in store for today and Sunday with gradual warming, into the low 60s. - Warming and drying trend continues into Memorial Day and early next week. - Chance for more widespread rain arrives Tuesday PM into Wednesday. && .AVIATION... High pressure extending from central Canada into the Midwest maintains a light NW wind and a cool air mass across Lower Mi today and tonight. The cool air and daytime instability support a lower cloud component again today but which is more firmly in low end VFR outside of a few MVFR pockets this morning. High pressure drifting closer to Lower Mi maintains light NW wind but aids in a cloud decrease tonight into Sunday morning. For DTW/D21 Convection... No thunderstorms today or tonight. THRESHOLD PROBABILITIES... * Low for ceiling at or below 5000 feet this morning. High this afternoon. Low tonight. && .PREV DISCUSSION... Issued at 350 AM EDT Sat May 24 2025 DISCUSSION... Effectively dissolved nocturnal cloud field yields a clear and chilly sunrise for most this morning as the large-scale pattern begins to reorient, albeit rather slowly. Lower Michigan will reside along the interface between the subtropical jet and an amorphous upper low encompassing portions of The Northeast, the Great Lakes, and Ontario/Quebec. Expectation is for a retreating CVA response (toward the north) during the late morning and mid-day hours as mid- level geopotential heights build in from the south. While this ensures a period of active mid-level subsidence, a shallow cloud- bearing mixed-layer should offer sufficient lapse rates to generate pockets of weak ascent/sprinkles. Forecast soundings reveal a dry boundary-layer which could result in more virga than light rainwater as hydrometeors descend toward the surface. Given how Friday unfolded, the latest consensus CAM simulated 1 km dBZ field, and evidence of non-zero QPF chances per HREF/DESI, did make PoP revisions. Opted to raise PoPs to Slight Chance northeast of a line from Caro to Port Huron where the vorticity ribbon overlaps longest, and added sprinkle mentions southwest of the line, down to the I-75 corridor. Decent thermal gradient arises from southwest to northeast this afternoon with 850 mb temperatures of 3-4C near the Ohio Border and only 1-2C over The Thumb. This translates to highs just shy of 60F for The Thumb, and low to mid 60s elsewhere. A secondary mid-level circulation evident in GOES vapor imagery over western Ontario will link up with the southern stream jet and eject southeast across Lower Michigan on Sunday. The VortMax quickly gets sheared apart by the more dynamic jet flow which lends low confidence in a true convective response, but should still note ensemble agreement in +100 J/kg of SBCAPE (20-40 percent chance). With equilibrium levels rather shallow, and rumble of thunder will be isolated and infrequent. Went with another combination of Slight Chance PoPs for the northeast portion of the forecast area and sprinkle mentions further south. Incremental warming Sunday with highs in the low to mid 60s across Southeast Michigan. Ridge amplification extends into Lower Michigan Memorial Day ensuring drier conditions, but 850 mb temperatures will still run a bit cool at 5-7C (25th percentile is 6C). This corresponds with highs approaching 70F, which is still several degrees below climatological normals. Diffuse surface high pressure field extends across the region Monday into Tuesday morning keep winds light with an easterly component beneath diurnal cumulus clouds. A shortwave trough over the Desert Southwest phases with an orphaned upper low over The Dakotas Tuesday. This affords some potential for higher quality moisture advection up through the Ohio Valley and into southern Lower mid-week. Still a lot of moving pieces that need to properly fall into place to equate to higher confidence in showers for the local area. NBM Chance PoPs still seem appropriate at this juncture. Temperatures return to seasonal normals next week with cloudier periods leading to slightly cooler days Tuesday and Wednesday but still near the 70F mark. MARINE... A low pressure system will exit north of Lake Ontario today which will continue to reinforce northwest flow across the Great Lakes. High pressure then begins to fill in across the Great Lakes this weekend, centering over the region on Monday. This will support light winds and some extended periods of dry weather. Light northwest flow holds through early Monday, with veering to the northeast as the high pressure system arrives. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...None. Lake Huron...None. Lake St Clair...None. Michigan waters of Lake Erie...None. && $$ AVIATION.....BT DISCUSSION...KGK MARINE.......AM You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.