979 FXUS63 KGRR 041806 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 206 PM EDT Tue Aug 4 2026 .KEY MESSAGES... - Unsettled pattern over the next 7 days - Seasonable temperatures are expected through the forecast period && .DISCUSSION... Issued at 206 PM EDT Tue Aug 4 2026 - Unsettled pattern over the next 7 days Unsettled conditions are expected over the course of the next 7 days with upper troughing overhead or nearby much of the time. At the surface, mid summer moisture levels will be in place with dew points at least in the 60s if not around 70 degrees. This level of moisture combined with some mid level cooling due to troughing in the mid levels will set the stage for some build up of afternoon and evening instability each day. Bottom line is we are looking periodic chances for showers and storms through the period. The main question is trying to nail down the time frames for the best chances for showers/storms. As for the details, the first good opportunity for showers and storms will occur Wednesday into Wednesday night as a weak cold front moves in from the northwest. Chances actually begin late tonight as the front approaches in the northwest CWA. We have likely pops at times in our gridded forecast late tonight through Wednesday night. Most unstable CAPE values increase into the 500-1000 j/kg range at times so thunder is certainly possible. Locally heavy rain will likely be the main threat. The front goes south of the forecast area but remains nearby Thursday into Friday. Some model differences make the remainder of the forecast a bit lower confidence given a rather benign surface pattern. Given a predominant northwest flow/upper trough in the mid level it is hard to rule out at least small pops Thursday through next Monday. We could see some rain totals add up in spots through the 7 days, but rivers have plenty of room given low flows. Some short term advisories are certainly possible given the moisture values (approaching 2 inches at times). - Seasonable temperatures are expected through the forecast period Temperatures look to remain seasonable despite the upper troughing. 850mb temperatures are in the middle teens C which make highs in the 80s likely each day. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 145 PM EDT Tue Aug 4 2026 SCT to BKN 4-5kft CU field /VFR/ will continue through the afternoon away from Lake Michigan, thanks to diurnal heating and dew points in the low-mid 60s. CU will fade later this afternoon and this evening, as S-SW breezes around 10 kt today become light tonight. Attention then turns to a weakening cold front currently over WI. This boundary will weaken further and essentially wash-out as it moves into Lower MI early Wednesday. Still, with some moisture pooling along boundary and weak convergence, a small risk for showers warranted at MKG /after 08Z/ and GRR /after 12Z/. These showers may briefly produced MVFR vsbys. Elsewhere /AZO-BTL-LAN-JXN/ rain-free VFR conditions are expected through 18Z Wednesday with a light S-SW breeze. && .MARINE... Issued at 206 PM EDT Tue Aug 4 2026 Small Craft Advisory across our northern marine zones north of Whitehall continues into this evening. The event looks very marginal with 3-4 footers potentially in the outer reaches of the 0-5nm nearshore zone. It is for this reason we do not have a corresponding Beach Hazards Statement out. The winds and waves both look marginal, but the reason we decided to keep it out is that the winds are just beginning to increase with Big Sable recently hitting the 20+ knot range. Given we are just entering the time frame where the wind peaks, 200pm to 800pm where winds will peak around 20 knots. Confidence is fairly low though in reaching Small Craft conditions for any length of time. Feel the Ludington buoy will likely peak around 3 to 3.4 feet this evening. Otherwise, southwest winds of 10-20 knots will create some choppy conditions on Wednesday in the 1-3 foot range. Heading into Thursday the gradient becomes quite slack and quiet conditions are expecting on Lake Michigan. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 10 PM EDT this evening for LMZ848-849. && $$ DISCUSSION...Duke AVIATION...Smith MARINE...Duke

NWS GRR Office Area Forecast Discussion