484 FXUS63 KGRR 261058 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 658 AM EDT Sun Apr 26 2026 .KEY MESSAGES... - Quiet weather expected into Monday afternoon - Chances for showers and thunderstorms Monday night - Cooler and mainly dry latter half of work week && .DISCUSSION... Issued at 358 AM EDT Sun Apr 26 2026 - Quiet weather expected into Monday afternoon High pressure will bring quiet conditions both today and tonight. Low clouds should lift and scatter out in the midday hours leaving partly to mostly sunny skies. High clouds will begin to filter in from the west this evening a precursor of more impactful weather to come Monday evening and Monday night. Temperatures will be above normal for highs both today and on Monday. 60s today and 70s on Monday will be above seasonal norms. - Chances for showers and thunderstorms Monday night A positively tilted upper trough will extend from the Canadian Prairies on Monday extending southwestward through California. A shortwave will eject out of this western U.S. trough and emerge in the Plains tonight. The upper shortwave and its associated surface reflection will take aim on Wisconsin on Monday. The low will be a fairly stout 993mb low which will lift a warm front into Southwest Lower Michigan Monday afternoon and evening followed by a cold frontal passage late Monday night. An active period of weather will occur from Monday afternoon through Tuesday morning with rounds of showers and thunderstorms. Severe weather is possible. We are in a SPC Marginal risk for severe weather and given the wind fields this is reasonable. If instability trends upward, so will our severe weather risk. 850mb low level jet speeds average around 60 knots with a speed max in the mid levels pushing 70-80 knots. We are not lacking for deep layer shear (60-70 knots in the 0-6km layer). Models have remained consistent in showing 60F surface dew points and PWAT values of 1.5 inches. So plenty of moisture to work with. Models have remained resolute in the fact that instability will hold at very modest levels...500 to 1,000 j/kg. Given the push of rain/widespread showers and thunderstorms it is not out of the question that this is more of a rain producer than a severe weather producer. The lack of instability is the concern. The items that are going for at least some severe weather though are 1) the potent upper wave and 2) strong wind fields. Not a slam dunk threat for severe, but we will be monitoring. We will know more as the system comes into the HREF and NadoCast forecast windows with the 12Z runs. Stay tuned... - Cooler and mainly dry latter half of work week A secondary wave looks to pass by Lower Michigan on Wednesday on the southeast edge of the upper trough moving into the Great Lakes. We look to have rain showers moving through a decent portion of the forecast area. Beyond Wednesday conditions should be mainly dry Wednesday night through Saturday. It will be cooler than normal with highs trending back into the 50s. 850mb temperatures will be in the zero C to -5C range late in the upcoming work week. Frost and freeze wording will reappear in our discussions and forecasts for Wednesday night, Thursday night and Friday night. && .AVIATION /12Z TAFS THROUGH 12Z MONDAY/... Issued at 658 AM EDT Sun Apr 26 2026 Low clouds are moving from east to west across Southwest Lower Michigan at 12Z. These clouds should clear all of the TAF sites by 15Z. We expect VFR weather to then prevail the remainder of the day and tonight. Tonight high clouds will spread in from the west. Winds will be easterly at 5-15 knots today. && .MARINE... Issued at 358 AM EDT Sun Apr 26 2026 Surface high pressure sprawls across much of Ontario and Quebec this morning with ridging extending southwestward into the Great Lakes region. This setup will largely remain the case both today and tonight. This means a continued easterly offshore flow with limited wave action. Waves should be 2 feet or less through daybreak on Monday. Things change on Monday as the high pulls away to the east and developing low pressure in the plains takes aim at the Western Great Lakes. In fact a deep low, 990-995mb, will lift northeast through Wisconsin Monday night. The pressure gradient tightens on Monday and reaches a peak Monday night. Monday we will see southeast winds increase to 30 knots with the chance for gale force winds Monday night out of the south. Waves will steadily increase Monday and Monday night with waves in excess of 6 feet likely north of Grand Haven. Will hold off on marine headlines at this point, but they will be needed going forward. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke AVIATION...Duke MARINE...Duke

NWS GRR Office Area Forecast Discussion