Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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415 FXUS63 KGRR 192250 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 650 PM EDT Thu Sep 19 2024 .KEY MESSAGES... - Chance for Storms Tomorrow - Several Chances of Showers and Storms into Next Week && .DISCUSSION... Issued at 252 PM EDT Thu Sep 19 2024 - Chance for Storms Tomorrow Clouds begin to increase late tonight as an upper low tracking from the Northern Plains into Manitoba sends a trailing front towards lower MI, arriving in our area Friday afternoon and evening. Spotty showers will begin to move through the area around late morning to mid- day, then storms will be possible during the afternoon. Diurnal instability up to 1000 to 1400 J/kg (highest over southern lower MI) and bulk shear to 35 to 40 knots will support a few strong storms, with the highest chance in far southwest lower Michigan. Damaging wind gusts will be the primary concern with any strong storms. - Several Chances of Showers and Storms into Next Week The weekend starts off dry as a period of brief ridging and high pressure advects dry air across the area. Precipitation chances then increase later Sunday and especially Sunday Night into Monday. This is driven by a closed low over the southwest US ejecting into the main flow pattern and bringing ample moisture with it. Can`t even rule out a bit. Ensemble CAPE forecasts suggest the chance of isolated thunderstorms also exists. Grand Ensemble precipitation probabilities show the chance for a needed soaking rain is definitely there. Chances of over 0.5" of rain Sunday Night into Monday night is 40-60 percent and over 1 inch is around 10 percent. This weekend into into next week marks the start of a pattern shift as the ridge that has brought dry weather for over a week breaks. This change makes troughing the predominant upper-level setup. Several additional chances of rain are possible over this time period, however as is common with these setups, the timing of the shortwaves and associated rain showers is still not nailed down. Thermal troughing also causes 850mb temperatures falling to around 10C, translating to a near normal low to mid 70s for highs next week. && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 650 PM EDT Thu Sep 19 2024 VFR conditions will continue at all the terminals this evening and overnight. Fog is not expected overnight given that some light winds will persist near ground level with stronger winds aloft. Clouds will gradually move in Friday and scattered showers and isolated storms will develop at our western terminals around or shortly after midday and then by around mid or late afternoon at our eastern terminals. Brief reductions to MVFR and perhaps IFR are possible in heavier showers and isolated storms. && .MARINE... Issued at 252 PM EDT Thu Sep 19 2024 A weak cold front will bring a chance for scattered showers early Friday morning. Otherwise, expect offshore winds starting Friday with winds shifting southerly then westerly Friday afternoon following the passage of the front. Wave heights stay generally low through this weekend, with the highest waves to around 2 feet Sunday evening. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...Thielke/Thomas AVIATION...Laurens MARINE...Thielke