Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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636 FXUS63 KGRR 241148 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 748 AM EDT Fri May 24 2024 .KEY MESSAGES... - Potential for Severe Storms This Evening/Tonight - Potential for Severe Storms on Sunday - Turning A Bit Cooler with Showers Monday and Tuesday && .DISCUSSION... Issued at 349 AM EDT Fri May 24 2024 - Potential for Severe Storms This Evening/Tonight Quiet weather starts our day as we look to this evening for thunderstorm activity. A mid-level trough curls northwards from the northern Plains while a corresponding surface low over the Dakotas also pivots northeastwards into southeastern Manitoba/western Ontario. Thunderstorm activity will occur along a trailing cold front as it sweeps through the Upper Mississippi Valley and into Lower Michigan. Timing still seems to favor the 8pm to 2am window with storms entering the decaying phase as diurnal instability declines. An additional instability element to consider will be decaying shower activity/convection ahead of the main cold front convection and whether that activity will put a damper on available instability as the cold front arrives. The 0z HREF keeps MUCAPE sub 1000J/kg across most of lower Michigan with values up to 1000-1500J/kg nosing just into Berrien/Van Buren/Cass Counties. Storms will originate in Iowa and move east into Wisconsin and northern Illinois before arriving in lower Michigan late this evening. Wind gusts will be the primary hazard as storms develop in a linear mode with some bowing segments possible. While the SPC Outlook keeps the Slight Risk across far southwest Michigan, severe wind gusts will be possible up much of the lakeshore. Several hi-res models key in on the frictionless lake dynamics and advertise strong gusts as far north as Ludington as the front crosses Lake Michigan and arrives at the West Michigan lakeshore. - Potential for Severe Storms on Sunday A deepening low pressure system is forecast to be moving into the Great Lakes from the southwest on Sunday. The low reaches the low 990s mb by Sunday evening as it moves into the Northern Great Lakes. A warm front will be lifting north through Lower Michigan during the day with a cold front poised to move in during the evening. The low looks to be driven by a convectively generated lead vort within a broader trough moving our way from the Plains. Given the depth of the low, its not surprising wind fields are strong. 850mb LLJ strength is 40-50 knots and increasing into the evening. The mid level jet at 500mb is 50-60 knots. Deep layer shear is strong. Instability is forecast to be moderate to high as higher dew point air surges in with the warm front. At this point the SPC Day 3 outlook for Sunday is south of our area, but can see this creeping north into Lower Michigan with time as model differences are ironed out and confidence increases. All severe hazards could be in play on Sunday across the forecast area. - Turning A Bit Cooler with Showers Monday and Tuesday An upper trough gradually develops overhead as we head into the holiday and Tuesday. Showers will occur on both days but it will not be a total washout. Shortwaves will be working through the flow over the Great Lakes, so its hard to envision totally dry forecast periods Monday through Tuesday night. Upper ridging gradually works in for Wednesday and Thursday along with a surface high. Dry weather is expected Wednesday and Thursday. Temperatures also cool from the 70s on Sunday...back into the 60s for Monday through Wednesday. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 748 AM EDT Fri May 24 2024 A cold front will approach from the west today and move through the area tonight. A band of showers and thunderstorms are occurring ahead of the front this morning out in Iowa. We will see clouds lower and thicken some today, but we are expecting to remain VFR today with bases through 500pm above 10,000 feet. This evening showers and storms will try to move in from the west, but confidence is somewhat low in how widespread the storms will be in our area. MKG, GRR and AZO stand the best chance at storms with lesser chances to the east. 00Z to 04Z or so will be the best chance at storms across the area. Winds from the southeast this morning will shift to the southwest. && .MARINE... Issued at 349 AM EDT Fri May 24 2024 Marine conditons stay quiet through today, then waves build Saturday morning with increasing westerly winds. Waves peak around 3 to 4 feet Saturday mid-morning then quickly decline. Winds and waves build early Monday morning through Tuesday at which time conditons will be hazardous to Small Craft and waves and currents will be dangerous to swimmers. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke/Thielke AVIATION...Duke MARINE...Thielke