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Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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552 FXUS63 KGRR 151129 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 729 AM EDT Thu Aug 15 2024 .KEY MESSAGES... - Showers/storms through Friday - Rain chances persist into the Weekend && .DISCUSSION... Issued at 337 AM EDT Thu Aug 15 2024 - Showers/storms through Friday Clouds will increase this morning as low pressure over the northern Plains pushes an occluded frontal boundary toward the region. Initially, the lower atmosphere will be fairly dry. However, a seasonably strong LLJ will move over the cwa this afternoon and we`ll see showers and isolated thunderstorms develop. Generally, shear values remain aob 25 kts across much of the cwa. However, models point toward the southwest cwa this afternoon where shear values rise above 30kts. Any stronger storms would likely be found southwest of a Grand Rapids to Battle Creek line after 18z today. The occluded front is progd to move across the cwa tonight in conjunction with the leading edge of the upper trough and that will likely produce more storms. Shear values climb to around 40 kts just ahead of the front, so we could see a strong to severe storm late tonight. The surface low and upper trough move over the cwa Friday, keeping showers and storms in the forecast. While dynamics aren`t overly strong, shear values are marginal enough for perhaps some cell organization in a couple of the stronger storms; much of the cwa is in a marginal risk for severe storms. HREF ensemble probability matched mean qpf points toward the northern cwa as the area that could see over an inch of rain through Friday with the southern half in range for a quarter to half inch. - Rain chances persist into the Weekend Upper troughing evolves into a cut off low over the Great Lakes region by the end of the week. This will continue the chance of showers through Sunday as sfc low pressure slowly moves through.The rain should be ending by Sunday night as the low moves east. Fair weather with below normal temperatures is expected next week as northwest flow regime brings in an air mass of Canadian origin while the heat and humidity remains bottled up across the SW CONUS. There is a slight chance of showers by the end of next week as another upper trough approaches from the northwest, but moisture is limited. && .AVIATION /12Z TAFS THROUGH 12Z FRIDAY/... Issued at 728 AM EDT Thu Aug 15 2024 VFR conditions will continue this morning then showers will move in this afternoon from west to east with MVFR conditions by this evening along with rain and a few thunderstorms. Southeast winds will increase to 10 to 20 mph this afternoon. && .MARINE... Issued at 337 AM EDT Thu Aug 15 2024 As low pressure moves closer today, we`ll see winds increase from the SSE this afternoon. We issued a Small Craft Advisory for this afternoon through 06z Friday north of Grand Haven because that`s where the wind and waves will be the highest. Wind and waves will decrease late tonight. Wind and waves will increase south of Holland Friday night and Saturday behind the weak frontal boundary and a Small Craft Advisory may be needed there during that time. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement from noon EDT today through late tonight for MIZ037-043-050. MARINE...Small Craft Advisory from noon today to 2 AM EDT Friday for LMZ847>849. && $$ DISCUSSION...Ostuno/04 AVIATION...Ostuno MARINE...04