textproduct: Grand Rapids

KEY MESSAGES

- Small rain chances through Tue; Rain Likely Tue night/Wed

- Cooler with rain chances Thursday and Friday

- Limited forecast certainty this weekend

DISCUSSION

Issued at 246 AM EST Mon Nov 2 2026

- Small rain chances through Tue; Rain Likely Tue night/Wed

No changes to previous thinking in terms of overall expectations. Areas northwest of Grand Rapids, particularly around Ludington, could see precipitation beginning early Tuesday morning shortly after midnight. However this precipitation is expected to remain out of most of southwest Lower Michigan.

The best chances for rain will be late Tuesday night and Wednesday. Both SPC and machine learning guidance suggests that isolated thunderstorms are possible, which seems reasonable given that extremely strong integrated water vapor transport (based on the ECMWF ensemble) and isentropic ascent will aid in elevated convective destabilization. Elevated stability-altering processes like these don't tend to be parameterized well by global models, including the GFS, so this is where machine learning guidance can have an advantage by leveraging analogs associated with the overall moisture and kinematic environment.

Forecast precipitation totals continue to decrease with successive model runs. Instantaneous rainfall rates could be impressive; this would be quite concerning if the expected warm cloud depth was greater. Rain totals should be kept in check by this being a progressively moving system.

The lower expected rainfall appears to be related to the trough transitioning into a cutoff low over the midwest. At the same time, at the southern extent of the deteriorating trough, there looks to be a cyclonic wave break over the Lower Mississippi Valley associated with a separate upper PV max. Hence, the best forcing for ascent and resultant precipitation amounts now look to occur in the Gulf Coast states and TN Valley area. This also would reorient the low level moisture transport vectors to point more east of our area via low level PV generation associated with latent heat release in the precipitation area.

The final thing to note about Tuesday is that it will be extraordinarily warm with highs now expected to be in the mid 70s. Guidance continues to increase highs during this time. Wednesday also looks warm with highs approaching 70s.

- Cooler with rain chances Thursday and Friday

We may have a break in rain Wednesday night, as noted previously, but this is neither certain nor likely to be long duration. This is because the expected dry slot may miss us to the east. In any case, colder lower tropospheric air pours into the area Thursday night into Friday with 850mb temperatures dropping close to 0C. This will yield delta-T values in the lower/mid teens which is sufficient for lake effect rain. Based on wind direction, precipitation will be primarily across far southwest Lower MI.

- Limited forecast certainty this weekend

The upper pattern during this time looks wobbly and complex with ephemeral cutoff lows rotating through a broader trough over the Great Lakes. With steep lapse rates underneath the colder air aloft, it would be easy to squeeze out rain showers from even modest upper PV forcing. The latest guidance still does keep Saturday dry and Sunday a little wetter, but given the extremely poor predictability with this pattern, the weekend forecast will be subject to change a lot during the coming week.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1240 AM EST Mon Nov 2 2026

No changes to previous thinking. We expect MVFR ceilings to develop by late morning/early afternoon, then to drop below fuel alternate thresholds (2000 ft AGL) this afternoon/evening. IFR ceilings will be possible after 00Z, particularly at the southernmost terminals (AZO/BTL/JXN), but omitted this later detail for the sake of brevity. Precipitation is generally not expected, although can't be ruled out after 00Z at MKG.

GRR WATCHES/WARNINGS/ADVISORIES

MI...None. MARINE...Small Craft Advisory from 7 PM this evening to 7 PM EST Tuesday for LMZ844>846. Small Craft Advisory from 9 AM this morning to 7 PM EST Tuesday for LMZ847>849.