Marine Weather and Tide Forecast for Forestville, MI

DISCUSSION

Near zonal upper pattern continues for the midweek period allowing a series of diffuse, dumpy shortwaves to slide over the Great Lakes/lower MI. These disturbances aid in both lifting a weak warm frontal boundary north towards central lower MI today as well as advecting periodic waves of mid-level moisture into the state supporting widely scattered showers and storms (as seen early this morning). Overall PoPs remain fairly broad-brushed at 20-30% in running forecast as weaker forcing combined with sensitivity to frontal positioning and uncertainty to what degree remnant pieces of upstream convection survive the local drier low level airmass all lend to a low predictability, nebulous rain coverage. A break in rain chances is likely by mid morning through early afternoon as the first wave kicks east of the region. These chances then return late afternoon-evening as a second wave (currently generating convection over Iowa) reaches the western Great Lakes. Said convective remnants reach SE MI between ~18-22Z however the resident low level dry airmass works to weaken activity likely only resulting in spotty showers/storms. Additional scattered convection tied to a surge in theta-e advection then pushes in from the western Great Lakes between ~00-06Z with best coverage north of M-59- owing to closer proximity to the PV anomaly tracking over central lower MI. In both windows, lapse rates hover around 6.5-7 C/km with MLCAPE's sitting at several hundred J/kg supporting the chances for some embedded elevated thunderstorms within wider showers. 0-6km shear around 35kts will offer a low, but non-zero, shot for an isolated organized storm which would be capable of generating hail.

Weak mid-level height rises attempt to build over southern lower MI Thursday suppressing/greatly limiting any precip from shortwaves still traversing over northern lower MI. The majority of the area is expected to stay dry as a result, though there is a potential exception. There is signal among some high-res (and coarser models like the 00Z RGEM) for a backdoor cold front-lake breeze hybrid, driven by weak surface high pressure over northern Lake Huron, to drop across the northern half of the CWA, down to roughly the I-69 corridor. Solutions are divided on the strength of this low level forcing to generate pop-up (thunder)showers so for now have only inserted a base slight chance (15%) PoP to highlight. Deeper layer south to southwest flow below 500mb maintains warm advection into the area increasing 850mb temps to 10-11C and supporting highs around 80 Thursday for areas south of I-69. For areas north, it depends highly on the aforementioned backdoor cold front which would create a decent north-south temperature gradient with highs in the mid to upper 70s near I-69 and only 60s in the Thumb.

Large shortwave ejects out of the southern Plains late Thursday and lifts northeast over the Great Lakes for Friday. Rain looks to arrive by late morning-early afternoon as widespread showers work across the area through Friday night. Scattered embedded thunderstorms also likely, mainly in the afternoon-evening timeframe, as a few hundred J/kg of MLCAPE develop with peak diurnal heating. Flatter mid-upper wave decreases the degree to which Gulf moisture is able to get advected this far north with the core holding to our south over the Ohio Valley. That said PW values still increase over 1", well within the 90th percentile for the daily climo, supporting for heavier downpours and a soaking rain with QPF looking to fall generally between 0.3-0.6" (some locally higher amounts possible given t-storm chances). Broad northern Plains high pressure builds in by early Saturday morning ending further rain chances with dry conditions holding through the weekend as it drifts overhead.

MARINE

Light winds continue through the midweek period under the guise of higher pressure and a weaker pressure gradient. Any localized higher wind speeds will be found across northern Lake Huron with the southeast flow, where gusts around 20 knots will be possible this afternoon and evening. Otherwise, there will be the chance for showers or an isolated thunderstorm centered over Lake Erie into Lake St. Clair today, with additional low end chances extending into Lake Huron late tonight into tomorrow morning. The better chances for more widespread active weather and elevated winds enter Friday as the next low pressure system arrives over the state.

PREV DISCUSSION
Issued at 1206 AM EDT Wed Apr 23 2025

AVIATION...

Midlevel thetae advection in the presence of a jet entrance region has resulted in higher based shower and iso thunder activity over Southeast Michigan. Included a TEMPO for -TSRA at mbS to open the taf period. Modest moisture in the 4.0 to 7.0 kft agl layer Wednesday with steep midlevel lapse rates will bring the potential for shower and an isolated thunderstorm again after 18Z 4/22. Did issue a prevailing group for -TSRA at all locations Wed afternoon.

DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet tonight and Wednesday.

* Medium for thunderstorms Wednesday afternoon.



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