Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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161 FXUS63 KGRR 181854 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 254 PM EDT Wed Sep 18 2024 .KEY MESSAGES... - Warm and Dry into Tomorrow - A Few Showers Possible Friday - Rain Potential Remains From Sunday into Early Next Week && .DISCUSSION... Issued at 254 PM EDT Wed Sep 18 2024 - Warm and Dry into Tomorrow Upper level ridging in place will continue dry conditions through tomorrow night. With 925 mb temperatures around 20 and an inversion in place temperatures are expected to fall into the 50s tonight and 50s to low 60s tomorrow night. There is a signal for fog to develop again around daybreak along the I-94 and 127 corridors looking at soundings and HIRES guidance. Copy and paste today for tomorrow with highs in the low to mid 80s across the area. - A Few Showers Possible Friday Upper troughing will finally try to make some headway into the Great Lakes Friday. Strong low and mid level jets over Wisconsin Thursday will weaken as they advance eastward Friday. A weakening surface cold front, initially helping fire some robust convection across Wisconsin Thursday, will press east into Michigan Friday with a dying line of showers during the morning and no instability to work with. That said, the front is forecast to slow down and perhaps just wash out over the region. Depending on how far it advances, there is a chance that some surface based or at least elevated instability (perhaps a few hundred J/kg) could develop ahead of it by late in the day or evening, supporting a thunderstorm or two, though odds are not great. Overall, it seems the likely evolution on Friday will be a fading line of showers crossing the lake in the morning, bringing a few hundredths of an inch of rain to the lakeshore, then possibly a few additional showers / isolated storm during the afternoon or evening mainly west of US 127, with heavy amounts not expected. - Rain Potential Remains From Sunday into Early Next Week After a dry day Saturday, the upper pattern evolution Sunday into early next week is still a bit in question, though good agreement in the 500 mb pattern is shown between the ECE and GEFS means. An upper low across the Desert Southwest region this weekend is forecast to eject northeastward and potentially phase with upper troughing across the Northern Plains and Upper Midwest Sunday. In general, this will lead to a strengthening low level jet across the Midwest that should finally help bring better low level moisture to the region as PWATs increase to the 1.50"-1.75" range Sunday into Monday (perhaps lingering into Tuesday). There may be a warm front lifting through the area in that time frame as well. Given synoptic scale support for precipitation, there could be periodic thunderstorms as well if destabilization takes place. The ECE probability for 0.50" or greater from Friday into Tuesday (bulk of that starting Sunday) is 80% across most of the region, which is a fairly high probability. Raising that threshold to 1.00" or greater is showing about a 50% probability. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 114 PM EDT Wed Sep 18 2024 A similar setup for fog to impact the terminals appears in place for early Thursday morning. Model guidance (GFS LAMP, HRRR soundings) does suggest fog is most likely at AZO, BTL, LAN, and JXN especially in the 09z-13z time frame. Like today and yesterday, much of this may take until 14z-15z to totally mix out and dissipate. The HRRR soundings show less in the way of saturation at the surface than what occurred today, so maybe the 1/4 mile visibilities will be less commonplace. && .MARINE... Issued at 254 PM EDT Wed Sep 18 2024 Light onshore winds along the lakeshore will become more easterly overnight and to the southeast Thursday morning. Toward the afternoon expect winds to shift more onshore and continue the diurnal pattern into Friday morning. Wind pick up slightly up to 15 knots Friday with the potential for showers and storms Friday morning and afternoon. Winds and waves are expected to remain below Small Craft Advisory thresholds into next week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Hoving/RAH AVIATION...Hoving MARINE...RAH