


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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372 FXUS63 KGRR 141930 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 330 PM EDT Mon Jul 14 2025 .KEY MESSAGES... - Frontal System Moves through Wednesday and Thursday - Brief respite then another weather system possible this weekend && .DISCUSSION... Issued at 315 PM EDT Mon Jul 14 2025 - Frontal System Moves through Wednesday and Thursday Fair weather due to high pressure will continue to dominate the pattern through Tuesday. While the cumulus field will fill in daily, with a mix of sun and clouds, it should be a dry forecast into Wednesday. There will continue to be quite a bit of haze today due to smoke infiltrating the region from Canadian fires. Given the high pressure and weak flow, it could persist through tomorrow. The weather pattern this week will be dominated by a large upper level low situated over Hudson Bay. That upper level low will be the driver of a longwave upper level trough that will move through the US this week. Models are consistent in showing a robust moisture boundary that will extend across Nova Scotia, Quebec, Ontario and through the northern Great Lakes early Wednesday. Expect warm air advection out ahead of that boundary. An upper level shortwave should move through the Midwest Wednesday, increasing instability Wednesday afternoon. Moisture out ahead of that shortwave, along with diurnal heating and warm air advection could allow for isolated showers and storms Wednesday afternoon. While there are some questions on timing overall, models are in fair consistency on more organized convection possible late Wednesday into Thursday as the frontal system brings the previously moisture boundary through the region as it couples with mid level and upper level troughs. Latest NAEFS ensembles has 1.75 PWATS over the area through this timeframe with broad level moisture through Thursday. While official QPF remains around a quarter inch there is the potential for heavy downpours, especially considering the atmospheric set up and dynamics. Given that, WPC has the region in a marginal excessive rainfall out look for Wednesday into Thursday. - Brief respite then another weather system possible this weekend Zonal flow will situate itself over the Midwest and Great Lakes region latter in the week, with high pressure over the mid levels. This should keep moisture to the south and stifle daytime convection Friday into Saturday. The next forecast question will be where and when does the Saturday/Sunday system progress. There remains timing and strength issues. Overall trend brings another system with corresponding showers and storms through late weekend into early next week. a && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 128 PM EDT Mon Jul 14 2025 Canadian wildfire smoke is reducing visibility to 5 or 6 miles in portions of southern and mid Lower Michigan this afternoon. Improvement is possible tonight, although consensus of short-term model guidance leans toward shallow fog development at LAN and JXN between 08 and 12 Z. Daytime cumulus clouds this afternoon and tomorrow will have bases around 4,000 feet. Winds mostly below 10 knots. && .MARINE... Issued at 128 PM EDT Mon Jul 14 2025 Low waves and swim risk through Tuesday with a light southerly breeze. Thunderstorms are possible between Wednesday and Thursday. Winds becoming north on Thursday may increase the waves and swim risk. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT tonight for MIZ037>040- 043>046-050>052-056>059-064>067-071>074. MARINE...None. && $$ DISCUSSION...Ceru AVIATION...CAS MARINE...CAS