Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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690 FXUS63 KGRR 180713 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 313 AM EDT Wed Sep 18 2024 .KEY MESSAGES... - Continued hot and dry - Chances for showers Fri and Sun-Tue && .DISCUSSION... Issued at 312 AM EDT Wed Sep 18 2024 - Continued hot and dry. Today will be another in a long string of above normal temperatures and dry weather. Latest surface analysis shows sfc dewpoints near 60 over far southeast Lower...roughly 8-10 degrees higher than over the cwa. Short range models show the ESE wind flow pushing those higher dewpoints westward today. HREF cloud progs point toward some CU developing east of US-127 late morning/early afternoon. However, afternoon mixing will draw down drier air from aloft and tend to dissipate the cu throughout the afternoon; we`ll still be looking at a mostly sunny sky. The upper Rex block will remain intact through Thursday. Tonight will be a repeat of clear skies and patchy overnight fog, followed by another mostly sunny day Thursday. - Chances for showers Fri and Sun-Tue The slow breakdown of the blocking pattern late this week into next should spell an end to the persistent dry and sunny weather, with 80- degree days becoming less favored after Sunday. The upper levels in the northern stream will tend to transition to more progressive Rossby waves as a stronger North Pacific jet streak moves in next week. The interaction of the northern stream with the southern stream over the southern US, which will tend to be more stationary and prone to blocking, complicates the large-scale evolution of the pattern over the CONUS next week. The details on when specifically rain might occur next week are quite disparate in the ensembles. There is however some clustering in the ensembles for a minor chance of showers on Friday, followed by a somewhat better chance Sunday- Tuesday. There are even some plausible solutions for soaking rain amounts over 1 inch by Tuesday, though this is not yet the most likely outcome. Friday may have weak elevated instability to support thunder chances, especially in northern areas closer to the influence of the weak shortwave trough. The Sun-Tue timeframe will depend on the extent that a northern stream trough will dig into the Dakotas and upper Midwest, followed by the potential for a compact upper-level low in the southern stream to migrate out of the southwest US. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 140 AM EDT Wed Sep 18 2024 Consensus of short term guidance continues to indicate the potential for MVFR to IFR visibility with mist and patchy fog mainly between 10 and 12 Z. Air fields closer to Lake Michigan, such as MKG, have lesser potential. A few AWOS are already dipping into MVFR visibility. Fog and scattered low clouds should mix away with drier air aloft within a couple hours after sunrise, then there is high confidence in VFR for the remainder of the day. && .MARINE... Issued at 312 AM EDT Wed Sep 18 2024 Southeast winds 5 to 15 knots will result in 1 to 2 foot waves over the next couple of days. Dry weather is expected through Thursday. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...04/CAS AVIATION...CAS MARINE...04