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Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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263 FXUS63 KGRR 161744 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 144 PM EDT Fri Aug 16 2024 .KEY MESSAGES... - Periods of Showers/Storms through Saturday - Showers ending Sunday then fair and cool next week && .UPDATE... Issued at 1049 AM EDT Fri Aug 16 2024 The cluster of thunderstorms moving onshore near Muskegon is shown by the latest HRRR to track eastward over the next couple of hours. The storms are basically forming along a low level boundary in that region which extends down into parts of Kent County. Aloft there is some upper level divergence and instability was advecting into the west side of the convection. We did raise the probabilities for thunderstorms for the expected track of the storms. Waves have increased around the convection and some values were nearing 4 feet. Guidance suggests that they will gradually decrease on the backside of the storms. We ensured a moderate swim risk exists into the afternoon mainly north of Holland. && .DISCUSSION... Issued at 322 AM EDT Fri Aug 16 2024 - Periods of Showers/Storms through Saturday We are currently in a lull in shower activity. However, a thunderstorm complex near Chicago is slowly moving ENE toward Lower MI and may graze the southern cwa early this morning. Additionally, new convective development over central Wisconsin is moving east and if it holds together could impact the western cwa within a few hours. Low pressure over northwest WI is pushing an occluded front across the eastern portion of that state and an upper low is sending minor short waves east toward MI. As a result, mesoanalysis shows in uptick in shear and mid level lapse rates approaching Lake MI. We`ll likely see some storms develop by 09z. Even so, shear isn`t all that high and so svr storms aren`t expected early this morning, but it wouldn`t be out of the question. By mid morning, we`ll be in another lull as the first short wave moves east. The next short wave will approach toward 00z and so we`ll see an uptick in showers/storms by late afternoon. Generally, progd shear values are less than 25 kts this afternoon and so while we`ll likely see storms from late afternoon through this evening, we`re leaning toward them being non severe. The next short wave to rotate through the flow will arrive Saturday morning and we`ll see another uptick in showers/storms then that will carry through much of the day. Once again, limited shear will render the storms non severe. - Showers ending Sunday then fair and cool next week The rain should be ending by Sunday night as the upper trough axis and surface low finally kicks out to the east. Fair weather with below normal temperatures can be expected next week as northwest flow regime brings in surface high pressure of Canadian origin while the heat and humidity remains bottled up across the SW CONUS. Overnight lows will drop into the 40s in rural areas both Monday and Tuesday nights. 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 /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 139 PM EDT Fri Aug 16 2024 Widespread MVFR and occasional IFR ceilings and visibilities from earlier are slowly improving, with some sunshine trying to spread into the area from the southwest. While conditions should spend most of the afternoon VFR at most locations, showers and scattered thunderstorms are expected to begin redeveloping by mid afternoon, primarily affecting northern and eastern areas. A more widespread line of storms is likely this evening - generally between 6pm and 10 pm - to move in from Lake Michigan and sweep across Lower Michigan. Behind this line of storms, winds shift a bit to come from a due west direction and thunderstorms taper off to hit-or- miss showers. This showery pattern, with steadily worsening MVFR or even IFR ceilings and visibilities overnight and continuing throughout much of the day Saturday with only very limited improvement expected. && .MARINE... Issued at 322 AM EDT Fri Aug 16 2024 Wind and waves will remain below advisory criteria through Saturday as low pressure settles over the region. Isolated to scattered thunderstorms will remain in the forecast, though, and be a marine/beach hazard. Waves will increase a bit by Sunday and a Small Craft Advisory may be needed then. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...MJS DISCUSSION...Ostuno/04 AVIATION...AMD MARINE...04