Sunrise 6:41 AM   Sunset 8:43 PM Moonrise 12:00 AM   Moonset 7:31 AM

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LMZ846 Holland To Grand Haven Mi- 405 Pm Edt Sat Apr 27 2024
.small craft advisory in effect through Sunday morning - .
Through early evening - South winds 20 to 25 knots. Partly Sunny with a slight chance of showers and Thunderstorms. Waves 4 to 6 feet. Tonight - Southwest winds 15 to 25 knots decreasing to 10 to 15 knots toward daybreak. A chance of showers and Thunderstorms in the evening, then rain showers likely and a chance of Thunderstorms overnight. Patchy fog overnight. Waves 3 to 5 feet. Sunday - South winds 10 to 15 knots. Rain showers and a chance of Thunderstorms. Patchy fog. Waves 1 to 3 feet. Sunday night - Southeast winds 15 to 20 knots. Rain showers likely and a chance of Thunderstorms. Waves 1 to 3 feet. Monday - South winds 20 to 25 knots. Rain showers likely and a chance of Thunderstorms. Waves 3 to 5 feet. Monday night - Southwest winds 15 to 25 knots. Partly cloudy with a chance of rain showers. Waves 3 to 5 feet subsiding to 2 to 3 feet toward daybreak. Tuesday - West winds 15 to 20 knots backing southwest 10 to 15 knots late in the day. Sunny. Waves 1 to 3 feet. Wednesday - Southwest winds 10 to 20 knots. Mostly Sunny. Waves 2 to 3 feet. Thursday - Southeast winds around 15 knots. Rain showers likely and a chance of Thunderstorms. Waves around 1 foot.

LMZ800
No data

FXUS63 KGRR 272252 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 652 PM EDT Sat Apr 27 2024

KEY MESSAGES

- Scattered Severe Storms Possible Tonight

- Additional Showers and Storms Expected Sunday into Monday

- Pleasant weather on Tuesday

- Periodic shower chances and mainly above normal temps mid-late week

DISCUSSION
Issued at 301 PM EDT Sat Apr 27 2024

- Scattered Severe Storms Possible Tonight

A look at satellite shows that while plenty of diurnal cu demonstrate the unstable boundary layer present, there is no convective development thanks to a lack of forcing. Expect the afternoon and first part of the evening to remain dry, though an isolated shower or storm is not off the table.

Looking at tonight, a boundary sinking across Lake Michigan will provide a focus for storm development after 7-8pm. Given MLCAPE values of 800-800 J/kg and MUCAPE values of 800-1250 J/kg in 35-45 knot deep layer shear, multicell organization will be supportive of scattered wind gusts to 60 mph and hail to around 1 inch in diameter, mainly across the current SPC slight risk area from South Haven to Ithaca. A marginal risk is in place to the southeast where an isolated severe storm tonight cannot be ruled out. The primary threat will be through 2am. A second area of showers and storms is expected to move in along a warm front overnight bringing rain across the southern CWA

- Additional Showers and Storms Expected Sunday

Showers and storms continue into Sunday as the warm frontal boundary stalls across Central Lower Michigan aided by weak ripples in the 500 mb flow and forcing from a jet streak to the north, keeping the best coverage of showers and storms near and north of I96. Severe weather does not look likely at this time given that showers and clouds in the vicinity of the warm front look to promote less in the way of destabilization (MUCAPE over 500 J/kg mainly south of the warm front and main convection), and large scale forcing is on the weaker side. However, if instability can build further north and to a greater magnitude than currently forecast, organized convection cannot be ruled out. We will need to monitor this into Sunday.

Another concern Sunday will be for areas of locally heavy rainfall as mean cloud layer winds will be somewhat parallel to the warm frontal boundary meaning training of storms is possible. HRRR probability matched mean values suggest that rain from Sunday Morning to Monday morning could exceed the 1 inch mark in spots if convection can train repeatedly over an area.

Widespread rainfall spreads over the whole CWA Sunday night into Monday morning as better forcing arrives in the form of an approaching cold frontal boundary and vorticity maximum embedded in the parent trough as it ejects north. Thunderstorm chances continue into Monday as instability (MUCAPE around 1000 J/kg) develops ahead of a front that passes through the CWA Monday into Monday night.
Given decent shear, we will have to watch the extent to which instability builds ahead of the front for organized convection potential. However the extent of instability development remains uncertain at present. Rain chances wind down Monday night as the front passes through the area bringing notably drier air with it.

- Pleasant weather on Tuesday

The upper trough and surface fronts responsible for the relatively unsettled/showery/stormy weather Sunday and Monday will shift northeast of the region by Tuesday. This will set the stage for a very pleasant Tuesday. With surface high pressure ridging overhead, expect partly-mostly sunny skies, light winds, and temperatures slightly above normal /highs in mid 60s to near 70/.

Though the rest of the week won't be a washout, Tuesday looks to be the only day without at least some chance for rain.

- Periodic shower chances and mainly above normal temps mid-late week

Models/ensembles suggest that upper trough over the NW quadrant of the CONUS will eject a couple of short waves ENEwd across the Upper MS Valley and Great Lakes region mid-late week. WAA ahead of one progressive short wave and associated surface front will support a low chance (20-30%) of showers Wednesday. The better chance (50- 60%) for showers and storms arrives around Thursday as a more potent short wave and surface low /somewhat reminiscent of this weekend/ advances into the region. Current projections suggest surface low will be east of Lower MI by late Friday and Saturday, allowing cooler and more seasonable air to overspread the Great Lakes.

All in all, temperatures are expected to average somewhat above normal this week, with highs in the upper 60s to middle 70s Wed-Fri, before falling back in the low-mid 60s Sat. Normal highs for late April are in the middle 60s.

AVIATION /18Z TAFS THROUGH 18Z MONDAY/
Issued at 652 PM EDT Sat Apr 27 2024

Greatest confidence for VCTS exists at MKG late tonight, most likely after 04z. A broken line of thunderstorms has developed across southern WI as of this writing. This line is likely to push over Lake Michigan and impact areas north of MKG, but eventually a portion of this line will probably impact MKG or it may simply merge with additional SHRA/TSRA development across northern IL that will move into southern Lower MI after 06z. High likelihood exists for IFR to develop area-wide in the 06z-12z range as ceilings drop considerably with rich low level moisture moving in and lighter winds expected during the overnight and early morning hours. Future amendments may include VCTS or TSRA mention at additional sites depending on convective evolution beyond 06z.

MARINE
Issued at 301 PM EDT Sat Apr 27 2024

Going small craft advisory looks to be in solid shape as frequent gusts of 25-30 knots have been observed today. Winds calm below small craft criteria overnight with waves falling early Sunday morning. Depending on how much winds calm overnight, areas of fog may develop over the lake as warm moist air moves over the still cooler lake waters and continue into Monday. Conditions hazardous to small craft are possible Monday as waves and winds increase ahead of a cold front.

GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 8 AM EDT Sunday for LMZ844>849.

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