Sunrise 6:13 AM   Sunset 9:09 PM Moonrise 5:30 PM   Moonset 3:38 AM

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LMZ848 Whitehall To Pentwater Mi- 1005 Pm Edt Sun May 19 2024
Rest of tonight - Northeast winds 5 to 15 knots veering east after midnight. Partly cloudy. Waves 1 foot or less. Monday - South winds 10 to 20 knots. Rain showers likely and a chance of Thunderstorms. Waves 2 to 3 feet. Monday night - South winds 10 to 15 knots. Mostly cloudy with a chance of showers and Thunderstorms. Waves 2 to 3 feet. Tuesday - South winds 10 to 20 knots. Partly Sunny with a chance of showers and Thunderstorms. Waves 1 to 2 feet. Tuesday night - South winds to 30 knots. Rain showers and a chance of Thunderstorms. Waves 2 to 4 feet building to 6 to 8 feet after midnight. Wednesday - Southwest winds to 30 knots. Mostly Sunny with a chance of rain showers. Waves 6 to 8 feet. Thursday - Southwest winds 15 to 25 knots. Sunny. Waves 2 to 4 feet.Friday - Southeast winds 10 to 15 knots veering south. Sunny. Waves around 1 foot.

LMZ800
No data

FXUS63 KGRR 200600 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 200 AM EDT Mon May 20 2024

KEY MESSAGES

- Marginal Risk for severe storms Monday afternoon/evening

- Strong to Severe Storms Possible Later Tuesday into Wednesday

- Dry Weather Thursday into early Saturday

DISCUSSION
Issued at 335 PM EDT Sun May 19 2024

- Marginal Risk for severe storms Monday afternoon/evening

A shortwave trough is minoring out as it moves across the central Great Lakes on Monday with warm advection/isentropic ascent aiding the development of scattered rain showers and storms Monday morning into afternoon. Although instability is present with CAPE spiking up to around 1000 j/kg by afternoon, deep layer shear is limited to about 20 to 25 knots. The marginal risk for severe storms lingers into the evening as the leading edge of an MCS or MCV is coming across Lake Michigan and reaching western zones by 00Z as indicated by model guidance, including the Hi Res ARW and FV3.

This line or cluster of storms is pushing east and weakening by late Monday evening as instability decreases and the severe threat should be over by midnight. The main threat with these storms appears to be isolated downbursts in bowing line segments, but a tornado threat cannot be ruled out if local wind profiles are modified by the evolution of an MCV.

- Strong to Severe Storms Possible Later Tuesday into Wednesday

By Tuesday the presence of a strong low pressure system over the north-central United States plants lower Michigan firmly in the warm sector with dewpoints well into the 60s. This allows plenty of instability to build with MUCAPE values climbing to near and north of 2000 J/kg with near to above 30 knots of shear by Tuesday afternoon. Two rounds of storms are possible Tuesday. First, some scattered storms are possible Tuesday afternoon as the low-level jet moves in and warm front lifts north. Then more widespread showers and storms Tuesday night into Wednesday morning as the subsequent cold front moves through the CWA

Guidance is still split on when the cold front arrives and how fast it moves through. The ECMWF solution is more aggressive and has the frontal boundary clearing the area by 18z while the GFS and NAM support a slower front. The slower the front crosses the state, the more destabilization can occur ahead of the frontal boundary Wednesday for the Southeastern CWA As the low and mid-level jets overspread the region, shear ahead of the front climbs over 40 knots Wednesday bringing potential severe weather concerns focused on the southeastern portions of the area as CAPE values remain elevated if the slower front materializes.

Overall, some uncertainty remains in the timing of any thunderstorms which affects the finer details of severe weather potential.
However, later Tuesday into Wednesday the parameter space will be favorable for the chance of strong to severe storms. This will need to be monitored and details fine-tuned over the next few days.
Regardless, Tuesday will be warm and a bit muggy with temps well into the 80s. Highs Wednesday will generally be in the 70s but if the front slows some areas may reach the 80s.

- Dry Weather Thursday into early Saturday

Predominantly zonal mid-level flow and surface ridging is expected after the front exits later Wednesday. This combined with a lack of deep moisture will support not only dry conditions but even potentially a few sunny days Thursday and Friday with highs in the 70s. The next chance of rain and increasing clouds will be Saturday as a cold frontal boundary and shortwave approach West Michigan.
Though as expected at this range, differences in timing and position exist keeping some uncertainty as to exact timing and coverage of showers.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
Issued at 200 AM EDT Mon May 20 2024

Upstream convection over eastern Iowa at 06Z extrapolates into MKG/GRR shortly after 12Z, although some question as to whether or not it impacts the terminals south and east of GRR later this morning.

Other isolated/scattered diurnal development of showers/storms expected in the afternoon before a more widespread coverage of storms occurs this evening (between 00Z and 06Z Tue). In general expect VFR today with periods of MVFR/IFR possible in any showers and storms.

Wind fcsts are somewhat complicated today due to potential impacts from convection and eventual position of incoming warm front, but in general we should see southerly winds increasing to 10 to 20 kts by afternoon.



MARINE
Issued at 335 PM EDT Sun May 19 2024

Winds and waves should remain below Small Craft Advisory the next few days although locally higher winds and waves are possible in thunderstorms on Monday afternoon through Tuesday night.

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

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