Area Forecast Discussion
Issued by NWS Grand Rapids, MI
Issued by NWS Grand Rapids, MI
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792 FXUS63 KGRR 012350 AFDGRR Area Forecast Discussion National Weather Service Grand Rapids MI 750 PM EDT Wed May 1 2024 .KEY MESSAGES... - Risk for thunderstorms later Thursday into Thursday night - Warm with Periods of showers and storms ahead && .DISCUSSION... Issued at 259 PM EDT Wed May 1 2024 - Risk for thunderstorms later Thursday into Thursday night A stronger mid level vort max pivots northeastward from SD through MN during this timeframe. An associated low level jet lifts up through WI an into western Lower MI. Elevated instability advects in, especially Thursday night with 925 mb/850 mb LI`s lowering down to -2 deg C. Thus an increasing risk for thunderstorms will exist during this period. With the low level jet around, any stronger storm may result in stronger gusts. Deep layer shear is shown to be quite strong well west of the CWA then, but if a complex and track in from the west, we could see an organized gust front, mainly Thursday night. We will expand the likely POPs to include much of the CWA for Thursday night. - Warm with Periods of showers and storms ahead A slow moving upper level low moving through the upper Midwest and along the Canadian border will dominate the weather pattern through the weekend into next week. No major changes to forecast ahead. Mid to long range models continue to show a shortwave swinging around that large upper level low that will entrench itself over the Upper Midwest Friday. That shortwave will strengthen a frontal system that will bring a warm and cold front through the region Friday. There is strong moisture through the mid levels that correspond with a mid level shortwave, a decent mid level gradient and dry air behind the front. This should bring for substantial showers and storms Friday afternoon and evening. PWATs still look to be around 1.25 and dewpoints in the 60s. While upper level dynamics look to be beneficial, looking at soundings they are fairly moist so periods of showers look to be the trend. The cold front treks eastward Friday afternoon with showers and storms. As the upper level low moves northeastwards a tertiary trough swings through late Saturday which could bring some light scattered showers into Sunday m morning. The next best chance for showers and storms will be early next week as another large upper level low moves similarly as Friday`s system and drags another trough with warm moist air into the Great Lakes. Max Temperatures through this timeframe will be in the 70s with highest temperatures nearing 80 next week. Cooler air will reside along the lakeshore. && .AVIATION /00Z TAFS THROUGH 00Z FRIDAY/... Issued at 750 PM EDT Wed May 1 2024 High likelihood of VFR tonight and much of the day Thursday. Clouds above 10,000 feet will be streaming in tonight and during the morning, and by afternoon (after 16 Z), clouds around 6,000 feet should stream in, sometimes creating a ceiling. Those clouds at 6,000 feet may be unstable and convect with weak to moderate updrafts, possibly up to 15,000 feet, to produce scattered showers and a slight chance of a thunderstorm. Any passing showers during the afternoon-evening could produce downdrafts, given a fairly dry and well-mixed lower atmosphere, and temporarily disrupt ground-level wind speed/direction. && .MARINE... Issued at 259 PM EDT Wed May 1 2024 The winds and waves have largely fallen to under small craft advisory so we cancelled the headline early. The winds will increase again Thursday night as another low level jet moves in. Mixing heights and the winds at those levels suggest we will fall just short of small craft conditions. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. MARINE...None. && $$ DISCUSSION...MJS/Ceru AVIATION...CAS MARINE...MJS