


Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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686 FXUS63 KGRR 081714 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 114 PM EDT Tue Jul 8 2025 .KEY MESSAGES... - Smaller shower/storm chances today through Wednesday - Mainly dry Thursday and Friday - Better shot of widespread rain Saturday && .DISCUSSION... Issued at 341 AM EDT Tue Jul 8 2025 - Smaller shower/storm chances today through Wednesday We are starting out the forecast period with mainly some mid and high clouds floating overhead this morning. We are watching a few showers over Eastern Wisconsin that formed earlier on the leading edge of better instability and a weak 15-20 knot low level jet core traversing east. It is not out of the possibilities that one of these showers could survive, and affect the lakeshore counties later this morning. This will be a 10-20% chance, meaning most of the area will stay dry. The better chance for a few showers and maybe a storm will come later today through the first part of Wednesday. We will see the instability gradient at the sfc and aloft push over the area this afternoon. The chance for any one site to see rain is not very high, staying in the chance category. This is because overall moisture is limited with having lost the humidity in the last 24 hours, and not seeing any significant advection of better moisture back in. The best chance of this whole period will be across the eastern portion of the forecast area on Wednesday afternoon. This will be when we see forcing via the upper short wave, sfc front, and some moisture return by then with diurnal instability. - Mainly dry Thursday and Friday Upper ridging will build over the area on Thursday in the wake of the upper short wave and sfc front that moves through on Wednesday. Sfc ridging will pass right overhead on Thursday, before moving east by Friday. There is a weak short wave that moves in Friday, but the models are showing dry conditions persisting with a lack of moisture return by then. - Better shot of widespread rain Saturday One of the better chances for a more widespread rain event over the last few weeks is looking likely to affect the area centered on Saturday. We will have one wave currently offshore of Northern California that will approach the area early Saturday. As this wave moves in, a stronger wave will be diving in from the NW. The CA wave is looking to be enhanced by the wave coming in from the NW due to the divergence occurring ahead of the second wave. The moisture flow ahead of it is not ideal, but the synoptic forcing and low level jet transporting moisture ahead of it, combined with a diurnal boost will all bring higher chances of a rain Saturday. If some sunshine can occur ahead of the showers and storms with the front, instability will increase, and decent mid level winds in place will help support storm organization. Still a ways out yet to get into any more details at this point. We will see a break in the weather on Sunday, before another weak short wave and associated sfc front move in to bring another chance of rain on Monday. && .AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/... Issued at 114 PM EDT Tue Jul 8 2025 Isolated showers have been observed towards MKG this afternoon. However, based on low-level dry air virga to very light rain (no restrictions) would be observed. Increased, though still scattered, shower activity is expected beginning this evening as a warm front crosses the area. Have added -SHRA at AZO and BTL where confidence is higher and have left VCSH at all other terminals. Cannot rule out isolated thunderstorms but thunder chances are too low for TAF inclusion. Rain chances increase Wednesday morning, particularly for LAN and JXN as daytime heating builds instability ahead of a cold front. Will leave thunder out of the TAFs at present but thunder could occur with this round of showers as well. Will not include any restrictions given low confidence but MVFR conditions may occur in any showers, and particularly thunderstorms. && .MARINE... Issued at 341 AM EDT Tue Jul 8 2025 We will see a break today in the higher winds/waves that have been present the last few days, before another possible event develops on Wednesday. We will see flow from the SW become established today out ahead of the next incoming front for later tonight and early Wednesday. These winds should stay rather tame, generally under 20 knots. Wednesday, we will see the relatively weak cold front move through. We are looking at another of the type of event we saw Monday with a tight mesoscale pressure gradient setting up right along the lakeshore with the departing front and incoming ridge. Another set of marine/swim headlines are possible, but will hold off for now. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...NJJ AVIATION...Thomas MARINE...NJJ