508 FXUS63 KGRR 272311 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 711 PM EDT Tue Oct 27 2026 .KEY MESSAGES... - Brief warmup expected Wednesday - Weak cold front brings light showers Thursday - More chances for rain over the weekend and into next week && .DISCUSSION... Issued at 255 PM EDT Tue Oct 27 2026 - Brief warmup expected Wednesday In spite of the continued presence of a broad upper level ridge aloft, and low level winds that are slowly veering to the southeast, temperatures today are largely similar to what they were yesterday at the same time, if not a couple of degrees cooler even. This is largely due to the fact that notable warm air advection ahead of Thursday`s cold front has yet to take place, and mid/high clouds have likely stunted daytime heating at least somewhat. Throughout the day tomorrow though, a shortwave and associated surface low pressure system will round the top of the ridge across Minnesota and Ontario, and breezy south to southwest winds will develop locally in response. The resulting warm air advection from these increasing winds will produce a noticeable jump in temperatures tomorrow, likely around 5 to 8 degrees, bringing afternoon highs to near and slightly above 70 degrees and about 15 degrees above daily averages. While we will also see a modest increase in dewpoints, precipitation is expected to remain to our west for at least one more day, although we are likely to see a bit more cloud cover. - Weak cold front brings light showers Thursday As the shortwave/surface low moves off to the northeast into Quebec Thursday, it will drag a weakening cold front through the Great Lakes, which is expected to produce at least some shower activity across much of the lower peninsula during the day Thursday. The model depiction of this "event" has been relatively consistent over the past couple of days, with a narrow plume of increasing moisture (near 1 inch precipitable water) and meager elevated instability (100-200 J/kg of MUCAPE). While most areas will see at least some very light rain, our northwestern lakeshore counties are favored for more meaningful amounts, although even here there is only a 30-40% chance of exceeding 1/4 inch. Meanwhile, we still cannot completely rule out a few lightning strikes here and there, although model soundings do not suggest that this will be common. Showers are favored Thursday morning and afternoon, and should move southeast and diminish during the evening and overnight as the weakening cold front sweeps through the area. - More chances for rain over the weekend and into next week Temperatures Friday are expect to dip back down to near or slightly above average, resulting in another pleasant fall day similar to the last few. However, a model guidance continues to depict another shortwave attempting to climb the crest of the upper ridge over the weekend, bringing additional chances for showers at various times. While timing details remain nebulous, it appears that chances are focused over two rough windows: light, spotty showers sometime during the day Saturday (Halloween), and potentially more widespread showers late Sunday/early Monday. The lack of timing specificity and ensemble spread continues to limit precipitation probabilities to only around 20-40% at any given time, but late Sunday continues to be the most favored period for rain over the weekend. Meanwhile, there continues to be a consistent long-range model signal for a more substantial southern-stream trough and low pressure system early next week, with the potential to bring widespread rain to the Great Lakes. While ensemble spread remains significant at this time range, the ceiling of this event is a bit higher than its predecessors when it comes to the potential for a more soaking rain. Meanwhile, the potential for this system to produce early-season snow also appears to be low, with almost no representation in long range ensemble members and continued warm temperatures. && .AVIATION /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 710 PM EDT Tue Oct 27 2026 Sct-bkn mid/high clouds will continue to move over the terminals through the period. As high pressure drifts to the east, winds will gradually turn from the SE to the SW by the end of the period. && .MARINE... Issued at 255 PM EDT Tue Oct 27 2026 While wind speeds remain elevated (10 to 20 kt at times), they have turned out of the southeast and largely offshore, allowing waves to settle to near or below 2 feet throughout the nearshore waters. This will continue through the night and into Wednesday morning, but winds will slowly veer to the southwest and increase to between 15 and 25 kt by tomorrow evening. This will drive steep, building waves into the nearshore waters Wednesday night through Thursday, reaching heights of 4 to 6 feet. Winds will weaken and become westerly, then northerly, behind a cold front Thursday afternoon and overnight, allowing waves to settle. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...BRC AVIATION...04 MARINE...BRC

NWS GRR Office Area Forecast Discussion