Sunrise 6:44 AM   Sunset 8:41 PM Moonrise 9:57 PM   Moonset 6:18 AM

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LMZ847 Grand Haven To Whitehall Mi- 405 Pm Edt Thu Apr 25 2024
Through early evening - Northwest winds 10 to 15 knots. Sunny. Waves 1 foot or less. Tonight - Northeast winds 5 to 10 knots becoming east 15 to 25 knots after midnight. Mostly clear. Waves 1 to 2 feet. Friday - Southeast winds 15 to 25 knots. Partly Sunny with a chance of rain showers. Waves 2 to 3 feet. Friday night - Southeast winds to 30 knots veering south gales to 35 knots toward daybreak. Rain showers and a chance of Thunderstorms. Waves 4 to 6 feet building to 5 to 7 feet toward daybreak. Saturday - South gales to 35 knots decreasing to 30 knots late in the day. Partly Sunny with a chance of showers and Thunderstorms. Waves 6 to 9 feet. Saturday night - South winds to 30 knots. Rain showers likely and a chance of Thunderstorms. Waves 6 to 8 feet. Sunday - South winds 20 to 25 knots. Rain showers likely and a chance of Thunderstorms. Waves 3 to 5 feet. Monday - South winds 20 to 25 knots. Rain showers likely. Waves 4 to 6 feet. Tuesday - Southwest winds around 15 knots backing south late in the day. Sunny. Waves 2 to 3 feet.

LMZ800
No data

FXUS63 KGRR 252350 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 750 PM EDT Thu Apr 25 2024

KEY MESSAGES

- Another Cold Night

- Showers and Thunderstorms Arrive Friday Night

- Warmer with Rounds of Showers and Storms Saturday into Monday

DISCUSSION
Issued at 343 PM EDT Thu Apr 25 2024

- Another Cold Night

We have issued a Freeze Warning for interior sections and a Frost Advisory for the counties bordering Lake Michigan for tonight. The airmass will be modified a bit from last night and return flow begins late tonight as the surface ridge begins to move east, but model soundings still show an very dry airmass through 12Z Friday with precipitable water down near 0.15 inches. This should allow temperatures to drop quickly like last night. There could be some wind picking up by 12Z...but we still expect temperatures to drop to around 30 in the warning area and lower 30s in the advisory.

- Showers and Thunderstorms Arrive Friday Night

Return flow increases Friday but it will take a while to moisten the column of the very dry atmosphere and showers will probably hold off until Friday evening although clouds will be in the increase in the afternoon with isolated showers possible across the southwest zones late in the day.

A large area of isentropic ascent and strong warm advection pattern combine with the arrival of deep moisture to bring increasing chances for rain Friday night and elevated instability should be enough for isolated thunder and some heavier downpours late Friday night. We will keep the categorical POPs across the northwest half of the forecast area where the axis of deeper moisture and lift will be.

- Warmer with Rounds of Showers and Storms Saturday into Monday

Low confidence at present in convective trends for Later Saturday Afternoon and Evening. A conditionally favorable environment for organized convection will be present given MUCAPE values of over 1000 J/kg as moisture climbs in strong SW flow, and deep layer shear values climbing to 35-45 knots given the low and mid-level jets in place. However, this is contingent on storms being able to develop which is in question given weak to no forcing in place given the frontal boundary and shortwave remain to our west. If storms can develop, organized convection is possible which is covered by the current SPC marginal to slight risk across the CWA It will be breezy however with NBM probs of 90+ percent for gusts over 30 mph for much of the area and 10-20 percent for 40+ mph, with warm air advection somewhat limiting gust potential. NBM 20-30 percent precip chances seem reasonable later Saturday.

As the warm front sits to out north Sunday a second round of showers and storms is expected across Central Lower, especially in the northwest CWA towards Ludington aided by a shortwave to our northwest and the right entrance region of the upper-level jet.
Given CAPE values north of 1000 J/kg thunder is likely and deep layer shear is still decent so Sunday will need to be watched too.

Showers then expand across the CWA Sunday Night into Monday as the cold front drifts south before clearing the area Monday evening.
CAPE values on the ECMWF and GFS still look to be above 500 J/kg so thunder continues to be possible.

Dry conditions for Tuesday as a period of surface ridging drifts over the area before chances increase for showers increase Wednesday/Thursday as a shortwave drives through before a trough passes overhead.

850mb temperatures climb into the teens this weekend into early next week causing temperatures to climb into the 70s with low (around 10 percent) chances that areas exceed 80 degrees. Highs will be well into the 70s, which is over 10 degrees above normal, through at least Tuesday making it feel like summer.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
Issued at 750 PM EDT Thu Apr 25 2024

VFR conditions continuing over the next 24 hours with just some high level clouds above 12,000 ft arriving on Friday. Clouds will begin to thicken and lower toward/after 00Z Saturday as showers approach then eventually overspread the area from the southwest.
East sfc winds 5 to 10 kts tonight becoming southeast 10 to 20 kts on Friday with some gusts near 25 kts in the afternoon.

MARINE
Issued at 343 PM EDT Thu Apr 25 2024

Winds will increase on Friday and Friday night. A SCA may be needed by late Friday afternoon or evening continuing into early next week as a persistent pressure gradient keeps southwest winds elevated and waves building over 4 feet to as high as 8 feet north of Pentwater.

GRR WATCHES/WARNINGS/ADVISORIES
MI...Frost Advisory from 1 AM to 8 AM EDT Friday for MIZ043-050-056- 064-071-072.
Freeze Warning from 1 AM to 8 AM EDT Friday for MIZ044>046-051- 052-057>059-065>067-073-074.
MARINE...None.

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