Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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839 FXUS63 KGRR 211938 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 338 PM EDT Fri Jun 21 2024 .KEY MESSAGES... - Scattered Storms This Evening - Organized Convection with heavy rain Saturday into Saturday night - Drying Out and Cooler Sunday and Monday - Strong storms still possible Tuesday/Tuesday night - Pleasant stretch expected Wednesday into the weekend && .DISCUSSION... Issued at 331 PM EDT Fri Jun 21 2024 - Scattered Storms This Evening ML CAPE values were up to 1500 J/kg around the region and low level convergence was maximized over northeast zones. Effective bulk shear values were highest over northern zones from near Ludington to Harrison. PWAT values were near 2 inches. Thus isolated/scattered storms will continue to develop inland through the remainder of the evening with locally heavy rain. With the effective bulk shear elevated north, this is downstream of the cell now near Green Bay. We will need to monitor that feature as the environment downstream of it is quite unstable. - Organized Convection with heavy rain Saturday into Saturday night A low level jet forms upstream in IA overnight and then noses into northern parts of the CWA Saturday morning. The warm front will be up in this area as well. Thus showers and thunderstorms will likely expand over the northern zones during the day. The warm front will likely remain nearly stationary and that could support training echoes. With PWAT values up around 2 inches and forecast soundings suggestive of efficient rain, rainfall could be excessive in some areas. It`s still uncertain the exact location of where the front will stall out and where the convection will train, but that something to monitor closely in coming forecasts. An impressive warm sector sets up over the CWA Saturday afternoon. With strengthening wind fields, the risk for severe weather will increase. If any convection gets going near or just south of the warm front around our northern zones, the forecast deep layer shear is supportive for organized convection. Then during the evening, a stronger mid to upper level wave and associated cold front will be tracking in from the west. Instability will be sufficient for stronger storms. That in combination with the stronger deep layer shear could lead to a line of storms with stronger wind gusts. The main window for this to happen is after 00z Sunday. - Drying Out and Cooler Sunday and Monday Lingering light showers Sunday morning should give way to clearer and slightly cooler conditions by Sunday afternoon. Dry conditions persist through Monday into early Tuesday. Temperatures should back off into the lower 80s both days. Some breezy conditions on Sunday but generally in the 15 to 25 mph range. - Strong storms still possible Tuesday/Tuesday night Continuing to keep on eye on the set up of hot/humid air building from the south with MCSs tracking through the Great Lakes from the northwest. This is our target for any significant weather in the upcoming week and will have to continue to be watched for severe weather potential. - Pleasant stretch expected Wednesday into the weekend Once the last of the MCS exits by early Wednesday a pleasant stretch of weather should move into lower Michigan. Wednesday through Friday should be really nice with highs in the upper 70s to lower 80s with much less humidity than we`ve seen in recent days. Could see some heat return next weekend through much of next week but currently not looking as oppressive as what was experienced this past week. && .AVIATION /18Z TAFS THROUGH 18Z SATURDAY/... Issued at 127 PM EDT Fri Jun 21 2024 Some showers/thunderstorms possible the next 6 hours before a quiet stretch should enter the forecast area. eastern areas most favored for shower/storms this afternoon so included some vcsh for GRR and LAN. could be a repeat of some fog tonight into early sunday but confidence too low to include at this time. showers and breezy conditions begin to work in toward the tail end of the taf period. && .MARINE... Issued at 331 PM EDT Fri Jun 21 2024 A low level jet will arrive later tonight and persist into Saturday evening. This will likely lead to increasing winds and waves. Model projections suggest we will remain under criteria for small craft and beach hazards through much of Saturday. During Saturday evening there could be enough increase in the winds and waves to warrant some headlines. With several rounds of convection expected over the next 48 hours, they could impact the wind setup. For now we will hold off on a any headline issuance`s given the uncertainty. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Heat Advisory until 8 PM EDT Saturday for MIZ056-057-064>067- 071>074. MARINE...None. && $$ DISCUSSION...MJS/Maczko AVIATION...Maczko MARINE...MJS