Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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855 FXUS63 KGRR 220600 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 200 AM EDT Wed May 22 2024 .KEY MESSAGES... - Severe Weather Potential Tonight - Dry for Wednesday and Thursday; Rain Chances Return Friday - Rain Chances Linger Through the Holiday Weekend && .DISCUSSION... Issued at 350 PM EDT Tue May 21 2024 - Severe Weather Potential Tonight Not expecting more than scattered showers and thunderstorms through this evening before a squall line moves across Lake Michigan from Wisconsin and reaches the western zones around midnight. Flat shortwave ridging at mid-levels is apparently suppressing afternoon convection today, but heights will begin to fall as a negatively-tilted shortwave trough closes off over Minnesota accompanied by sfc cyclone tracking into Canada with a cold front advancing into Lower Michigan overnight. An analysis of model soundings and other model-generated severe weather probability guidance suggests the greatest chance for severe weather tonight will be across the western forecast area near the Lake Michigan shore. A line of storms in western Iowa at 330 PM EDT is progged to expand and move east, crossing Lake Michigan. Main threat for our nearshore waters and western forecast area is for downburst winds but transient QLCS mesocyclone circulations cannot be ruled out, resulting in enhanced swaths of higher winds and even a quick tornado. Model soundings suggest instability decreases as the storms move east and some of the model guidance show a corresponding weakening of the line of storms before they reach Grand Rapids. The front becomes more parallel to the environmental winds on Wednesday slowing and stalling near or south of the forecast area with lingering showers possible near JXN during Wednesday. - Dry for Wednesday and Thursday; Rain Chances Return Friday Good forecast certainty remains for a dry Wednesday and Thursday and this will be accompanied by much more seasonal highs in the 70s. Humidity will be substantially less oppressive too with dewpoints dropping into the 50s and then 40s by Thursday. GOES satellite water vapor channels show an upper PV maximum currently diving southward into the Pacific Northwest region. This feature will eventually emerge as a cyclonically breaking upper wave over the Upper Mississippi valley region Friday afternoon/evening. Strong upper divergence with this feature will support a solid coverage of showers and storms pushing eastward into our forecast area Friday night, although the best QG forcing should remain well northwest of our area. This combined with nocturnal stabilization should limit the threat for severe thunderstorms. - Rain Chances Linger Through the Holiday Weekend Unfortunately, forecast details for Memorial Day weekend remain quite uncertain. A brief lull in precipitation for at least part of Saturday seems probable, but that`s about as definitive as I want to get right now. Starting Saturday afternoon, PoPs for the rest of the holiday weekend look to be in the neighborhood of 20 percent, which is right around climatology. High temperatures will be quite close to climatology as well in the neighborhood of low 70s. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 200 AM EDT Wed May 22 2024 A cold front is situated north to south over portions of Central Wisconsin. Ahead of the front a decaying line of showers and storms are occurring. At this point we have left all thunder chances out of the TAFs as it looks like the front will come in largely if not completely dry. Behind the front over Western Wisconsin, MVFR ceilings are in place. The front and the lower ceilings will progress into Western Lower Michigan around 12Z. Lower ceilings (MVFR) will spill into the TAF sites during the course of the morning. MKG will be most impacted by these ceilings as they will stay in the bulk of the day. By mid afternoon, most places should be back to VFR. It looks like the frontal boundary will pass through the area dry so we are expecting no restrictions to visibility through the TAF period. South to southwest winds of 15 to 25 knots can be expected the remainder of the night and through the daytime hours of Wednesday. && .MARINE... Issued at 350 PM EDT Tue May 21 2024 No changes to the Small Craft Advisory. In addition to strong southwest winds from the tightening pressure gradient, there could be gusts over 50 knots tonight as a squall line moves across Lake Michigan, arriving in the nearshore area around midnight. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for LMZ844>849. && $$ DISCUSSION...Ostuno/TJT AVIATION...Duke MARINE...Ostuno/Thielke