894 FXUS63 KGRR 140648 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 248 AM EDT Mon Sep 14 2026 .KEY MESSAGES... - Showers and Storms Tuesday, Heavy Rain and Isolated Severe Possible - Low Predictability Heavy Rain Possible Into The Weekend && .DISCUSSION... Issued at 247 AM EDT Mon Sep 14 2026 - Showers and Storms Tuesday, Heavy Rain and Isolated Severe Possible Conditons should be dry today with high pressure in place across the area, before a low deepening in the RRQ of an upper-levle jet will drive a warm front across the area early Tuesday with a cold front later Tuesday bringing shower and thunderstorm potential. Low-level destabilization in conjunction with increased shear from a westerly jet will support a low chance for gusty winds south of I96. Depending on where the boundary stalls, PWATs over 2.0" will be supportive of a heavy rain threat as well, subject to that placement. - Low Predictability Heavy Rain Possible Into The Weekend Predictability falls into mid to late week as the front stalls just south of the area, with an upper-level pattern dominated by zonal flow with embedded shortwaves. These patterns are notoriously hard to pin down. Cluster analysis suggests while there may be dry periods, there`s not great confidence as to when they will be. A stalled boundary with persistent high PWATs favors the heavy rain threat continuing with a WPC Marginal to Slight ERO in place. Another mid-level wave, low-level jet, and surface low fall into place going into this weekend. This will bring additional shower/thunderstorm potential. && .AVIATION /06Z TAFS THROUGH 06Z TUESDAY/... Issued at 125 AM EDT Mon Sep 14 2026 Skies are generally clear areawide with the exception of lake effec stratocu affecting MKG. Satellite trends suggest this should largely be FEW to SCT, with intermittent cigs around 5kft possible at times. Clouds then increase in coverage Monday afternoon and night with cloud bases lowering to near 10kft by the end of the TAF window. Light and variable winds are expected tonight before increasing from the southeast Monday afternoon and night. && .MARINE... Issued at 247 AM EDT Mon Sep 14 2026 Conditons deteriorate tonight into Tuesday as an approaching surface low deepens increasing southerly flow. Enough of a signal for 35-40 knot gales exists north of Holland to hoist a Gale Warning, with a Small Craft Advisory south of Holland for 22-33 knot gusts. Gales persist into Tuesday morning with conditions hazardous to small craft continuing into Tuesday night. Will also hoist a Beach Hazards Statement from Allegan County north for waves as high as 12 feet. Will leave Van Buren county out for now with the caveat a 10-20 degree on shore wind shift will bring waves from the 2-4 ft to 3-5 ft range bringing a high swim risk. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from this evening through Tuesday evening for MIZ037-043-050-056. Beach Hazards Statement from this evening through Tuesday afternoon for MIZ064. MARINE...Small Craft Advisory from 10 PM this evening to 5 PM EDT Tuesday for LMZ844-845. Gale Warning from 10 PM this evening to 8 AM EDT Tuesday for LMZ846>849. && $$ DISCUSSION...Thomas AVIATION...Thomas MARINE...Thomas

NWS GRR Office Area Forecast Discussion