507 FXUS63 KGRR 071148 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 648 AM EST Sat Mar 7 2026 .KEY MESSAGES... - Storms sweep through the area this morning - Mid week system to bring rain - Turning colder behind the mid week low with chances for snow && .DISCUSSION... Issued at 302 AM EST Sat Mar 7 2026 - Storms sweep through the area this morning A cold front is sweeping east into portions of Western Wisconsin and Eastern Iowa at 230am. Temperatures ahead of the cold front in the warm sector over Illinois are in the middle 60s which is obviously anomalous at this time of night in early March. The warmth is being brought northward via a strong low level jet at 850mb on the order of 60 knots. The low level jet is forecast to sweep east through Southwest Lower Michigan between 400am and 1000am. It is during that time frame where we expect storms to sweep through. In terms of instability we certainly have enough for convection as both the HRRR and the SPC mesoanalysis page indicates 1000-1500 j/kg of MUCAPE to work with. Hodographs are showing plenty of shear with 50 knots of deep layer shear (0-6km). The bulk of that shear is in the 0-1km layer. So in the CAPE/Shear balance both factors are well accounted for. Looking at forecast soundings though there is a low level stable layer in place, so not sure spin ups are much of a threat. Strong winds and hail are certainly higher threats, although the stable layer will aid to inhibit winds to the surface a bit. Given the strength of the wind fields with adequate instability we will be monitoring storms closely for all threats this morning. We are still in a marginal threat for severe storms through 12z by the SPC. We will likely see another quarter to half inch of rain this morning as the storms move through. This will add to rising river levels. We issued a River Flood Warning for Sycamore Creek in Holt. Not expecting many more warnings, but could be another one or two depending on how things play out. We will be watching the Red Cedar in East Lansing closely. Storm totals thus far have been highest from the Grand River basin southward where 1-2+ inches of rain has been fairly common. - Mid week system to bring rain A mid week system will move through the region bringing rain from Tuesday afternoon into Wednesday. The GFS has a further south track of the low (more along the MI/IN line) versus the ECMWF that takes the low further north into the state. The differences in track result in the GFS having more in the way of snow across Central Lower Michigan whereas the ECMWF is mainly rain. At this point feel the ECMWF is the way to go with more rain than snow. That said, both models pull in colder air behind the system with rain changing to snow before it ends. Only light accumulations of snow are expected for the most part (an inch or less). - Turning colder behind the mid week low with chances for snow The colder air that is pulled in behind the Tuesday/Wednesday system will linger into the end of the week when a clipper quickly moves through the Great Lakes. This system has a chance to put down a swath of snow but at this point the track is not certain. The ECMWF is the further south bringing us better chances for snow. We have time to keep an eye on this system and dial in the track as we move forward. Bottom line a bit of an up and down forecast with warmth to start the 7 day period and colder air with snow towards the end of it. A pretty typical scenario for early spring in the Great Lakes. && .AVIATION /12Z TAFS THROUGH 12Z SUNDAY/... Issued at 639 AM EST Sat Mar 7 2026 Light rain showers continue to move across the terminals early this morning. Although a thunderstorm or two may develop prior to 16z, confidence is low that it would affect a TAF site and was left out of the TAFs. A cold front will move across the region prior to 18z and end the convective threat once it moves by. Ceilings will be MVFR throughout the afternoon and skies will scatter out overnight. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...04

NWS GRR Office Area Forecast Discussion