Sunrise 6:13 AM   Sunset 9:08 PM Moonrise 6:32 PM   Moonset 3:59 AM

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LMZ845 South Haven To Holland Mi- 1032 Pm Edt Mon May 20 2024
Rest of tonight - Southwest winds 10 to 15 knots. Partly cloudy. A chance of showers and Thunderstorms through about 2 am. Waves 1 to 3 feet. Tuesday - South winds 10 to 15 knots. Mostly Sunny with a chance of rain showers and a slight chance of Thunderstorms. Waves around 1 foot. Tuesday night - South winds to 30 knots veering southwest toward daybreak. Rain showers likely and a chance of Thunderstorms. Waves 2 to 3 feet building to 4 to 6 feet after midnight. Wednesday - Southwest winds 15 to 25 knots. Sunny with a chance of rain showers. Waves 4 to 6 feet. Wednesday night - West winds around 15 knots. Mostly clear with a chance of rain showers. Waves 2 to 3 feet. Thursday - West winds 10 to 15 knots. Sunny. Waves 1 to 2 feet. Friday - East winds around 10 knots backing northeast late in the day. Mostly Sunny. Waves 1 foot or less. Saturday - South winds 10 to 15 knots. Partly Sunny with a chance of rain showers. Waves around 1 foot.

LMZ800
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FXUS63 KGRR 210552 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 152 AM EDT Tue May 21 2024

KEY MESSAGES

- Marginal Risk of Severe Weather This Evening

- Slight Risk of Severe Weather Tuesday Night

- Chance of Storms Wednesday

DISCUSSION
Issued at 305 PM EDT Mon May 20 2024

- Marginal Risk of Severe Weather This Evening

Multiple lines of convection from Lake Michigan to southern Wisconsin and northern Illinois this afternoon will be moving into Lower Michigan this evening. Latest radar trends are showing a weakening of the storms over Lake Michigan but these storms could strengthen again as they move back over land with 500 to 1000 J/kg of MUCAPE to work with. The main threat is isolated wind damage with the strongest convection. The severe threat will diminish with loss of sfc heating this evening. The showers will be exiting the eastern zones around midnight.

- Slight Risk of Severe Weather Tuesday Night

There should be a lull in the convection as the first shortwave trough minors out/moves east and is replaced by flat ridging before heights fall again late Tuesday afternoon and evening as the next shortwave trough axis swings through along with increasing shear profiles and deep lift. Scattered convection in the afternoon will give way to increasing POPs as organized convection along and ahead of the cold front pushes in from the west.

Primary threat will again be scattered wind damage with stronger updrafts or bowing line segments, but model soundings from the GFS and NAM show possible QLCS tornado threat with favorable low level helicity as near sfc winds veer strongly with height.

- Chance of Storms Wednesday

The front bringing the chance for severe weather Tuesday night continues to drive south and east during the day on Wednesday. The GFS/NAM have trended towards the ECMWF suggesting the front clears our southeast CWA in the vicinity of 18z Wednesday. Given how early the front clears the area, the potential for convective redevelopment is uncertain. There are signals for the potential of showers and storms to develop south and east of Grand Rapids, mainly down towards Jackson, Wednesday afternoon and evening aided by a passing vorticity maximum.. If any development can happen on the warm side of the front, a strong to severe storm cannot be ruled out given 40-45 knots of deep layer shear hence the current marginal risk for severe storms. Rain chances end early Thursday.

Dry weather is expected Thursday into Friday as surface ridging aided by zonal flow at 500mb ridging by Friday and little to no deep layer moisture. The lack of moisture also keeps plenty of sunshine in the forecast with highs well into the 70s Thursday and Friday.

An lead shortwave ahead of a parent trough approaches early Saturday increasing clouds and rain chances, further increasing Saturday and into the day on Sunday as a weakening surface low sends a front through the area with renewed cyclogenesis over the central Great Lakes. Exact timing and placement of important features, as expected over 5 days out, is still uncertain but the broader signal across guidance is generally similar. So, while timing and extent of any precipitation is uncertain, the chance does exist for rain during the memorial day weekend. This means the NBM 30-40 percent PoPs are appropriate for the end of the week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/
Issued at 152 AM EDT Tue May 21 2024

Stratus and fog will produce IFR/LIFR conditions through 14Z or so before mixing out, mainly north of a AZO to LAN line. Otherwise VFR conditions prevailing from mid morning into the evening before a possible squall line races across Lk MI toward Midnight.
Southerly winds will increase substantially after 02-03Z tonight in front of that approaching line, with LLWS becoming likely.

The timing of the line of strong to severe storms tonight is toward the very end of the TAF period, but if the line holds together there could be gusts as high as 50 kts associated with it shortly after Midnight.

MARINE
Issued at 305 PM EDT Mon May 20 2024

Offshore winds and waves below 3 feet through Tuesday although there could be some locally strong winds and choppy waves in the vicinity of thunderstorms this evening and again Tuesday night.

Winds will pick up Tuesday night and Wednesday with waves building to 6 to 8 feet Wednesday morning.

GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...None.

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