DISCUSSION

A compact mid level low across Wisconsin this afternoon will traverse the straits tonight before lifting north of Lake Huron on Saturday. Cloud cover expanded across much of Se Mi today within the entrance region of an upper jet. Areas of light showers/sprinkles and an early convective release has limited available instability over most of the area with the exception of the Saginaw Valley. An additional Short wave impulse pivoting around the upper trough and entrance region upper jet support will keep some focused ascent across the Saginaw Valley and points north this evening. This will be the most probable locations for additional late day deep convection. ML Cape Values hovering around 1k J/kg and 0-6km shear values of 40-50 knots may still support isolated strong/convection.

The upper low will transition to an open wave as it exits to the northeast on Saturday. Reasonable model agreement indicates a trailing trough axis advancing from northeast Lower Mi into the Saginaw Valley/thumb regions by late afternoon. This added boundary layer convergence within weak instability will support a chance for deep convection late Saturday across the north. Low level thermal profiles will be cooler tomorrow (925mb temps a few degrees cooler).
This and the expectation for some cloud cover (morning low clouds transitioning to sct-bkn diurnal cu field) will support highs in the 70s.

Sunday into Monday, Se Mi will lie between a low level anticylone across the eastern Great Lakes and brad mid level troughing across the upper Midwest/western Great Lakes. The proximity to the anticyclone will keep convective chances low at least through mid day Monday. Persistent southwesterly flow will drive warmer air into Se Mi, supporting highs well into the 80s Sunday and near 90 Monday. An eastward progression of the long wave trough will support increased chances for convection late Monday into Tuesday, with slightly cooler temps expected in its wake by mid week.

MARINE

Low pressure tracks across Lower Michigan this evening and into Lake Huron tonight with scattered showers and thunderstorms continuing to track east to northeast at around 30 knots. Isolated storms may be severe, capable of producing wind gusts in excess of 35 knots, hail, and waterspouts. Showers and storms will decrease in coverage and intensity tonight with light wind shifting to northwest as the low departs and sends a weak cold front through. Isolated to scattered showers linger into parts of Saturday as troughing is slow to release from the region. Light winds continue into Sunday with sunnier skies as a weak ridge of high pressure builds in from the south. Southerly wind of 10 to 15 knots then develops on Monday ahead of the next frontal system moving in from the Midwest. This system will bring showers and storms late Monday into Tuesday as it tracks through.

PREV DISCUSSION
Issued at 216 PM EDT Fri Jul 5 2024

AVIATION...

Ample amount of shear and CAPE exist to sustain scattered thunderstorms this afternoon and late evening. Several storms have already developed INVOF MBS along a convergence boundary while thunderless showers crop up over the Metro Detroit terminals.
Expectation is that most thunderstorm activity will hold off until late this evening for FNT south, thus the later TEMPO group adjustments. Clouds are largely expected to remain high-based, but a brief BKN high-MVFR ceiling could arise early this afternoon. Light to modest southwest winds drop-off overnight with some HZ reintroduced Saturday morning. Potential exists for low-MVFR ceilings/visibilities overnight, but not confident enough for inclusion for the 18Z TAF cycle. Borderline MVFR ceilings should settle in Saturday morning with stratus favored amidst the cooler post-frontal airmass.

For DTW/D21 Convection...Scattered showers are expected this afternoon along a pre-frontal trough with storms more likely to develop this evening ahead of an inbound cold front. Will highlight the earlier period with -SHRA then target the late evening (01-04Z)
period for thunder. Storms will generally be single cellular or multicellular with SW-NE storm motion.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms between 18Z and 22Z today, then medium between 01Z and 04Z this evening.

* Low for ceilings at or below 5000 ft this afternoon then medium late tonight into Saturday.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.