889 FXUS63 KGRR 251836 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 236 PM EDT Wed Mar 25 2026 .KEY MESSAGES... - Brief Window for Strong to Severe Thunderstorms Thursday - Below Normal Temperatures Friday and Saturday - Potentially Unsettled Weather Next Week && .DISCUSSION... Issued at 236 PM EDT Wed Mar 25 2026 - Brief Window for Strong to Severe Thunderstorms Thursday Overall, there is a short period of concern for a few thunderstorms to potentially reach strong to severe levels Thursday late afternoon through evening across extreme southern Lower MI (roughly 4pm-9pm), but the better setup for severe weather will likely take shape across IL/IN/OH. Details are as follows. As has often been the case this month, a surface warm front will be located near or just south of the I-96 corridor Thursday afternoon. A 40kt LLJ will develop during the day and converge across northern IN and near the MI/IN border. Between 12z-18z, low-mid 50s dewpoints will advect in southern Lower MI while 60+ dewpoints will be confined to south of the MI/IN border. Given mediocre low level moisture, it`s not surprising that it will be struggle to obtain a few hundred J/kg of either SBCAPE or MUCAPE in our region. For the I-96 corridor, most likely we are just looking at some late afternoon and evening showers with perhaps a rumble of thunder. Further south, 12z HRRR guidance shows a few hours of 7-8 C/km mid level lapse rates near the I-94 corridor from 19z-22z. If any cells can develop in that region there may be some hail. Taking a 12z HRRR sounding near our southern border over Berrien County at 22z shows 0-3km shear of nearly 70 kts but 0-3km CAPE of zero and CINH of -300; MUCAPE is shown to be around 800 J/kg. Unless 1) convectively driven gravity wave interactions occur to tap some stronger winds above the stable layer or 2) significant enough precip loading occurs via downward momentum of hail and liquid water, it`s unlikely that damaging winds of 60 mph or greater will materialize in our southern region and are more likely to occur near and south of the MI/IN border. The same holds true for a more supportive environment for tornado development being across northern IN based on the latest 12z HREF 2-5km updraft helicity swaths and associated STP values of 1-2 there, coupled with supporting Nadocast projections of higher tornado percentages near and south of South Bend, IN. - Below Normal Temperatures Friday and Saturday Temperatures will tank Friday after cold frontal passage and 850mb temperatures drop from about +10C Thursday to around -10C Friday. Highs will range from the mid 30s to low 40s both days which is about 10 to 15 degrees below normal for late March. - Potentially Unsettled Weather Next Week Global ensemble data is in good agreement regarding a synoptic pattern change by the early to middle portion of next week. ECE/GEFS/CMC ensemble mean 500mb heights and vorticity indicate a shift from a dominant ridge across the SW U.S. to an orientation more across the SE U.S. as deep upper troughing begins to set up across the West Coast. This places the Great Lakes in a region of deeper southwest flow and already there are signs of anomalous PWAT values surging into the region by Tuesday or Wednesday. Depending on frontal positioning, this could lead to a rather wet pattern heading into the midweek period. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 208 PM EDT Wed Mar 25 2026 VFR weather is expected the remainder of the afternoon and most of if not all of tonight. Ceilings drop to MVFR and IFR around daybreak on Thursday. South winds are in place across the entire area at 18z with a cold front situated well to the northwest of the area over the Northern Plains. Over the next 24 hours, the front will drop southward and push into Southwest Lower Michigan Thursday morning. The front is on the move due to a strong area of high pressure advancing southward from Canada. VFR ceilings and visibilities are expected through 10z tonight. After 10z a rapid development of MVFR and quickly to IFR is expected. By 13z to 14z all 6 TAF sites should have ceilings below 1,000 feet and visibilities in the 3-5 mile range. It appears much of the rain with the front will hold off until just beyond the valid time of these TAFs, 18z to 18z. A gusty south wind of 10-15 knots with gusts over 20 knots can be expected through 00z or so. After 00z, the winds should drop into the 7-12 knot range. && .MARINE... Issued at 236 PM EDT Wed Mar 25 2026 Increasing southerly flow over Lake Michigan this afternoon has led to an uptick in waves and there are whitecaps visible on Manistee webcams. A Small Craft Advisory is in place from Whitehall to the north into late tonight with waves peaking in the 2 to 5 foot range this evening. Another SCA will be needed for much of the nearshore waters Thursday afternoon into Thursday night. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until midnight EDT tonight for LMZ848-849. && $$ DISCUSSION...Hoving AVIATION...Duke MARINE...Hoving

NWS GRR Office Area Forecast Discussion