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Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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174 FXUS63 KGRR 142329 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 729 PM EDT Sun Jul 14 2024 .KEY MESSAGES... - Showers and Thunderstorms this evening and again Monday night - Diminishing Rain Tuesday then Cooler and Dry to End the Week && .DISCUSSION... Issued at 354 PM EDT Sun Jul 14 2024 - Showers and Thunderstorms this evening and again Monday night Chose to roughly follow the HREF forecast for POPS tonight since it seems to be a decent compromise for the wide range of solutions in the CAMs. The idea is that convection will initiate in the next few hours across Iowa and southern Wisconsin as an MCV moves through an area where the airmass fully recovered from last night`s convection. The storms move east and expand into another MCS in WNW flow with the southern half or third of the forecast area with likely POPs and some risk of severe weather, mostly downburst winds. These storms should be clearing the eastern forecast area around 06Z followed by a break in the action before the next round arrives Monday afternoon as heights being to fall and surface cold front settle south, with an MCS expected to form somewhere upstream across the Dakotas or Minnesota and dive SE into Wisconsin, northern Illinois and eventually southwest Lower Michigan. The general signal in the synoptic pattern has been there for several days, but the details on the mesoscale have been quite variable and uncertainty remains. It seems the main threat will be strong downbursts in a progressive type derecho regime with the highest chance for severe winds across the southwest forecast area, late afternoon Monday into Monday night. - Diminishing Rain Tuesday then Cooler and Dry to End the Week The cold front continues to get shoved southwards early in the day Tuesday, then shower chances diminish by the afternoon. Upper troughing moves in overhead with a weak shortwave presenting low rain chances Wednesday afternoon across north central lower Michigan. Surface high pressure builds in from the west Wednesday evening with dry weather to persist through the end of the week. Noticeably cooler conditions expected starting Tuesday following the passage of the cold front Monday. Highs near 80 Tuesday, then into the 70s through the end of the week. Dewpoints will also fall resulting in less humid conditions. Overall, expect pleasant and quiet weather with comfortable temperatures and plenty of sunshine to end the week. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 729 PM EDT Sun Jul 14 2024 A few showers may clip KAZO and KBTL over the next 1-2 hours as they weaken coming off the lake. Otherwise a line of storms developing to our west will arrive at the lakeshore after 03z, and progress east through all terminals. MVFR visibilities are expected in any storms. While low confidence, gusts exceeding 30 knots are possible in the strongest storms. Have added a TEMPO group for the best window for storms at each site. The areas that see heavy rain will likely see MVFR visbys and cigs and IFR cannot be ruled out. However, given the dependence on the track of the heaviest rainfall, have not included restrictions with these TAFs and will amend as favored areas for low cigs/visbys becomes clearer. A break is expected mid morning through early afternoon with scattered storms possible after 18z, and particularly after 21z. Confidence in timing and placement of storms is low given dependence on how ongoing storms progress so will leave storms out of the TAFs tomorrow afternoon. The strongest storms will be capable of gusts exceeding 40 knots. Otherwise, expect scattered to broken cumulus tomorrow with gusts to around 20 knots. && .MARINE... Issued at 354 PM EDT Sun Jul 14 2024 Winds and waves will continue to stay below hazardous levels for mariners and swimmers, except for the potential for some strong thunderstorms this evening and again Monday night. THese storms could create locally higher waves and wind gusts over 35 knots. Some areas of marine fog are also possible through Monday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057- 064-071. MARINE...None. && $$ DISCUSSION...Ostuno/Thielke AVIATION...Thomas MARINE...Ostuno