840 FXUS63 KGRR 042353 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 753 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 /00Z TAFS THROUGH 00Z THURSDAY/... Issued at 750 PM EDT Tue Aug 4 2026 Dissipating CU early and then mainly clear skies for the majority of the tonight /VFR conditions/. An approaching weak cold front will spread clouds and a small risk /30%/ for showers into the MKG/GRR areas late tonight and early Wednesday -- after 08Z at MKG and after 12Z at GRR. However, front and scattered showers don`t make it much farther S/E -- as front parallels upper flow and stalls. Still expect BKN clouds /4-8kft/ to develop in most areas Wednesday. TAFs currently do not include thunder anywhere, though daytime heating in the presence of weak front may support a few storms after 19Z in vicinity of MKG/GRR/AZO. Winds throughout the TAF period will be from the S-SW, 5-10 kt tonight, and only around 10 kt Wednesday. && .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...None. && $$ DISCUSSION...Duke AVIATION...Smith MARINE...Duke

NWS GRR Office Area Forecast Discussion