


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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206 FXUS63 KGRR 150536 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 136 AM EDT Tue Jul 15 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 /06Z TAFS THROUGH 06Z WEDNESDAY/... Issued at 136 AM EDT Tue Jul 15 2025 The haze that was present earlier has diminished per the improvement in visibilities at the terminals. KJXN saw the improvement briefly, and then saw fog settle in. It seems that the southern terminals have the best chance of some fog with dew points a bit higher. KJXN will see the worst conditions as is typical due to the site being in a low spot. Any fog will burn off/mix out quickly after sunset. Skies should remain mostly clear outside of any isolated fog/stratus. A few cumulus clouds are likely, but should not cause any impacts being few-sct. Winds will become more from the SSW in the afternoon, and will go light from the SSE after sunset. There is a small chance of a shower developing at KAZO and KBTL in the last couple of hours of this forecast period as a few move up from the south. These should not be anything of consequence. && .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...None. MARINE...None. && $$ DISCUSSION...Ceru AVIATION...NJJ MARINE...CAS