Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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178 FXUS63 KGRR 300522 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 122 AM EDT Sun Jun 30 2024 .KEY MESSAGES... - Slight chance of storms this evening, then cool and breezy Sunday - Moderating Temperature Trend Next Week - Chance for Thunderstorms Late Tuesday into Wednesday && .UPDATE... Issued at 926 PM EDT Sat Jun 29 2024 No changes planned to the current forecast. We are seeing thunderstorms moving eastward across northeastern Lower MI at this time ahead of a pronounced upper PV max crossing the Upper Peninsula per water vapor satellite imagery. We also have showers crossing central Lower MI a little farther to the south and this includes our northeastern forecast area. But, forcing is less pronounced even this slight distance south of the thunderstorms. The central Lower MI activity also is quickly exiting to the east. Hence, we are looking at only a very narrow window of opportunity for thunderstorms in the Clare/Mount Pleasant area. Farther south, a surface boundary is pressing southeast towards the southern Lower MI state line. There could be a brief window for a shower just east of Jackson given a northward moving outflow boundary that may constructively interfere with the southeastward moving boundary. Again though, we are looking at a very narrow window of opportunity for what would be a low probability, low impact scenario at this point anyway. && .DISCUSSION... Issued at 332 PM EDT Sat Jun 29 2024 - Slight chance of storms this evening, then cool and breezy Sunday There are two chances we`re watching for development of storms in our area for the rest of today. The first is in the far south/southeast counties, where substantial instability and moisture (dewpoints in the mid 70s) continue. There`s enough shear in the column to potentially maintain some organization if anything gets going, but the missing ingredient in this area is a trigger/forcing mechanism. A weak shortwave moving across southern Lake Michigan earlier tried to initiate some convection, but things never really took off. As the evening progresses, we`ll be watching what happens as the surface cold front sags into our area around 00z from the northwest. It looks like the best chances for storms will remain south of the Michigan/Indiana border (where lift, moisture, and instability all overlap better), but can`t rule out a stray storm trying to clip our southern areas. Meanwhile, better atmospheric lift will also exist in Northern Lower Michigan this evening associated with impressive 500 mb CVA associated with the upper trough, which will move into Lower Michigan around the same time as the surface cold front. Some discrete convection and possibly a few strong to severe storms could develop, but the best lift stays north of our area, so again we`re thinking that we`ll be on the edge of the threat area. All of this adds up to a situation where we`ll be watching closely for severe risks this evening, but the most likely scenario is that any severe storms stay just to the north and south of our area. By midnight, the cold front will have come through the area, and we`ll fall under the influence of northwest winds and cooler (and drier) air moving in. These clearing skies and gusty winds will continue all the way through Sunday, with a dangerous swimming day along all Lake Michigan beaches expected for the day Sunday. See the Marine section below for more info. - Moderating Temperature Trend Next Week It will be seasonably cool Monday with high pressure and northeast winds which will keep high temps in the 70s. A southerly flow waa pattern will develop on the back side of the departing ridge beginning Tuesday. Max temps will reach the upper 70s to lower 80s Tuesday and well into the 80s to near 90 degrees by Wednesday. - Chance for Thunderstorms Late Tuesday into Wednesday As a warmer and more humid airmass advects into our area there will be a chance for a few showers and thunderstorms Tuesday into Wednesday. However the greater risk for convection and severe wx should stay off to our west across Iowa and southern Wisconsin Tuesday where stronger instability is forecast to develop along with forcing from the cold front. The boundary will bring a chance of showers and storms into Wednesday. However the boundary should tend to stall and wash out with not much of an airmass change at all for our area mid to late week. So while there is a relatively low risk for a shower or storm Tuesday and Wednesday we expect that dry and increasingly warmer and more humid conditions will prevail the majority of the time. The focus for convection should be south of our area Thursday and then a system approaching from the west will bring another chance for showers and storms Friday. && .AVIATION /06Z TAFS THROUGH 06Z MONDAY/... Issued at 118 AM EDT Sun Jun 30 2024 A cold front will push south of the TAF sites in Lower MI over the next few hours. Some MVFR clouds were slipping down from the north and it appears they will impact the TAF sites for a few hours this morning. As the atmosphere dries out later this morning and into the afternoon, the clouds will break up leading to mostly clear conditions. Occasional gusts over 20 knots will be possible through the day, from the north northwest. && .MARINE... Issued at 332 PM EDT Sat Jun 29 2024 A small craft advisory and associated Beach Hazards statement has been issued for all of our marine areas starting this evening and continue through late Sunday evening. As winds shift around to the northwest (and eventually north), waves will build into the 4 to 6 foot range as wind gusts in excess of 25 knots are possible in all areas. The worst conditions are still expected Sunday morning, but winds and waves don`t really start to drop significantly until later Sunday afternoon into the evening hours. Cool temperatures and a possible upwelling event (leading to much cooler water temperatures) should both limit beach populations on Sunday, but sunshine will still draw a crowd, so staying safe in the water will be critical for this early-holiday weekend. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Beach Hazards Statement through this evening for MIZ037-043-050- 056-064-071. MARINE...Small Craft Advisory until 10 PM EDT this evening for LMZ844>849. && $$ UPDATE...TJT DISCUSSION...Laurens/AMD AVIATION...MJS MARINE...AMD