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Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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005 FXUS63 KGRR 050008 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 808 PM EDT Thu Jul 4 2024 .KEY MESSAGES... - Chances for showers and storms Friday into Friday Night - Mainly dry this weekend with seasonable temperatures - Seasonably warm with a risk for showers/storms next week && .DISCUSSION... Issued at 353 PM EDT Thu Jul 4 2024 - Chances for showers and storms Friday into Friday Night Chances for an isolated rain shower will continue this afternoon and evening as a shortwave slides through the Southern Great Lakes. Chances for a widespread wetting rain are very low given the dry air that remains in place below cloud base. The focus really shifts to Friday afternoon and evening as a deeper trough moves in from the west. The HREF shows precipitation trying to slide in during the morning and then a distinct redevelopment in the afternoon after about 100pm-200pm. Deep layer shear is formidable with 40-50 knots. MUCAPE values reach around 1000 j/kg. Given the deep layer shear there will be storm organization. The HREF shows multiple updraft helicity swaths especially in our northeast CWA, so there is a severe threat. We are not expecting widespread severe storms, but some localized wind/hail is certainly possible. We would not be surprised to see the marginal severe threat area expand from SPC into more of our forecast area with later updates as we head into day 1 (Friday). Precipitation will be very much diurnally driven so we expect a loss in coverage and intensity quickly after sunset. - Mainly dry this weekend with seasonable temperatures In the wake of Friday`s system, look for weak cyclonic flow to linger into Saturday at the surface and aloft - especially early Saturday. This may support a stray diurnal shower (20%) east of US- 127, though most areas will remain dry. With some clouds around Saturday /again, mainly early/ highs will only reach the mid 70s - just a bit below normal for early July. Models agree that surface ridging will then provide dry and warmer weather Sunday, as high temperatures reach the lower 80s. - Seasonably warm with a risk for showers/storms next week The early and middle part of next week will feature a continued summerlike pattern, with periodic chances (30-50%) for showers and storms. Timing the specific windows for the shower/storm risks will be difficult, given the interplay between daytime heating, and the passage of weak upper disturbances embedded within broad/weak 500 mb trough located over the northern Plains and Great Lakes. The next impulse aloft and associated weak surface trough are forecast to move into the Great Lakes from the WNW Monday and Tuesday, bringing a chance (40-50%) for showers and storms. At this time, the signal for strong to severe storms appears low. Ensemble data suggests the aforementioned broad/weak troughing aloft over the northern CONUS will start to give way to higher heights. However, this weakly forced summertime set up, coupled with daytime heating, will still support a low (20-30%) chance for storms through late week. Highs will be within a few degrees of normal for early-mid July (low to mid 80s). All in all, a very normal pattern for early- mid July. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 753 PM EDT Thu Jul 4 2024 A few very isolated showers have formed this evening around West Michigan as max diurnal heating has been reached over the last few hours. Most places will remain dry, though one of these showers just went over the Grand Rapids airport. These will all diminish over the next few hours, resulting in a VFR night with generally light winds. Latest model guidance suggests some low clouds may form/move into the I-94 corridor after midnight, taking advantage of weak flow and plenty of humidity/moisture in the lowest levels of the atmosphere. Currently not thinking this will be an overly significant impact to the TAF sites, but will monitor future trends. Meanwhile, better chance for showers and some storms is still expected by tomorrow morning along the lakeshore and spreading inland by late morning. In general it seems like this line of showers/storms will come through a bit too early to take advantage of the diurnal instability, but some storms may produce gusty winds and hail through early afternoon Friday. && .MARINE... Issued at 353 PM EDT Thu Jul 4 2024 There are limited chances for significant wind in the next few days, so we are not expecting Beach Hazard Statements or Small Craft Advisories. Tonight, wind is lighter than 10 knots. On Friday into Friday night we have a low that moves through the area, so south winds will shift to the northwest through that period. Winds will reach the 10 to 20 knot range at times Friday and Friday night. This should not be enough to create winds/waves that reach BHS/SCA criteria. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Duke/Smith AVIATION...AMD MARINE...Duke