Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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150 FXUS63 KGRR 260140 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 940 PM EDT Wed Sep 25 2024 .KEY MESSAGES... - Small rain chances Saturday through Tuesday - Drier and cooler mid-week next week && .UPDATE... Issued at 940 PM EDT Wed Sep 25 2024 Added patchy fog into the forecast for late tonight / early Thu morning for parts of the area. Consensus of short-term models is leaning toward the better chance of fog being west of US-131, where already the Ludington and South Haven AWOSes are reporting dips in visibility. The forecast thermodynamic soundings in the HRRR and ARW do not seem as robust for fog as they were a few times last week, but it will be close in spots, enough for shallow fog patches, as forecast min temps should drop a couple degrees below the crossover temperature. && .DISCUSSION... Issued at 258 PM EDT Wed Sep 25 2024 - Small rain chances Saturday through Tuesday Fair weather with drier air arriving overnight through Thursday. Confidence is increasing that we will remain dry for Friday, and see small chances for rain showers beginning Friday night and lasting into Tuesday. Many of the various models and ensemble members continue to show what is left from "Helene" will be absorbed by the Upper Low centered near AR/TN/MS on Friday. The strength of the upper high over our area and the upper low will wrap it back to the NW, but keep most of the system south of the area. What we will see from this scenario is we will see moisture advect in from the SE, and weak short waves rotating on the northern flank of the combined upper low complex. Much of the period from Saturday through Monday will be dry. There will be periods when short waves move through, combined with diurnal instability that will fire off a few showers and even isolated storms at times. The air with this system will not be that cold with the tropical part of this. - Drier and cooler mid-week next week Eventually what will happen by Monday night/Tuesday is we will see a strong upper jet and associated upper wave dive toward the area. This is a strong enough system that it will boot the weekend upper low out. This system will arrive with a strong cold front, and a chance of showers and storms. The flow ahead of the front will not be favorable for much rain with the front. The front is forecast to move through at some point on Tuesday. The frontal passage looks to end rain chances at that point, and it will cool the air down markedly as 850 mb temps drop from the low/mid teens C, to the lower single digits C by Wednesday. This will support highs in the 60s and lows in the 40s. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 746 PM EDT Wed Sep 25 2024 VFR expected to be prevalent tonight and Thursday although cannot rule out some MVFR or lower vsbys in fog late tonight and early Thursday (mainly between 08Z and 13Z). Given the low confidence in overnight fog formation/coverage, have maintained the earlier strategy from the 18Z TAFs of carrying a 4-5 hr period of VCFG in most of the TAFs. && .MARINE... Issued at 258 PM EDT Wed Sep 25 2024 Winds are expected to remain below 20 knots and waves below 3 feet into the weekend. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ UPDATE...CAS DISCUSSION...Ostuno/NJJ AVIATION...Meade MARINE...Ostuno