Sunrise 6:15 AM   Sunset 9:07 PM Moonrise 3:21 PM   Moonset 3:03 AM

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LMZ847 Grand Haven To Whitehall Mi- 1105 Am Edt Sat May 18 2024
Rest of today - South winds 10 to 15 knots. Sunny. Waves 1 foot or less. Tonight - South winds 10 to 15 knots veering southwest toward daybreak. Partly cloudy with a slight chance of rain showers and isolated Thunderstorms. Waves around 1 foot. Sunday - Northwest winds 10 to 15 knots. Mostly Sunny. Waves 1 to 2 feet. Sunday night - North winds 5 to 10 knots veering southeast 10 to 15 knots toward daybreak. Partly cloudy with a slight chance of showers and Thunderstorms. Waves around 1 foot. Monday - South winds 10 to 20 knots. Partly Sunny with a chance of rain showers and a slight chance of Thunderstorms. Waves 1 to 3 feet. Tuesday - South winds 10 to 20 knots. Mostly cloudy with a chance of showers and Thunderstorms. Waves 1 to 3 feet. Wednesday - Southwest winds 20 to 25 knots. Partly Sunny with a chance of rain showers. Waves 4 to 6 feet.

LMZ800
No data

FXUS63 KGRR 181724 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 124 PM EDT Sat May 18 2024

KEY MESSAGES

- Very mild weekend

- Low chance of showers late tonight and Sunday afternoon

- Wet Monday through Wednesday, Strong storms possible Tuesday

UPDATE
Issued at 1100 AM EDT Sat May 18 2024

Only change was to drop the Marine Dense Fog Advisory earlier as there is no sign of fog patches remaining anywhere on Lk MI on visible satellite imagery, even out over the open waters.
Otherwise a picture perfect Saturday is underway with no changes needed to the fcst.

DISCUSSION
Issued at 333 AM EDT Sat May 18 2024

- Very mild weekend

Summerlike conditions are forecast this weekend with high temps reaching the low to mid 80s today and Sunday (except cooler near Lake MI as a weak gradient is conducive for lake breeze formation today and tomorrow). Ample sun is expected today after patchy early morning fog with nothing more than some sct-bkn fair wx cu late this morning and aftn mainly near to east of US-131.

- Low chance of showers late tonight and Sunday afternoon

A weakening line of showers and perhaps an isolated storm will move in from the wnw into our nw fcst area very late tonight. The vast majority of our area will not receive measurable rainfall overnight.

Then for Sunday a weak frontal boundary will focus development of a few showers and isolated storms mainly east to se of KGRR in the aftn. Moderate instability will develop SE of KGRR with sb capes reaching 1k-2k j/kg. However no svr wx is expected given weak shear and weak forcing and limited moisture.

- Wet Monday through Wednesday, Strong storms possible Tuesday

Southwest flow aloft is usually a setup that can be stormy across the Great Lakes during the spring and that will be the case here Monday through Wednesday. Of the three days, Tuesday will garner the most concern.

A short wave will track from the central Plains toward Wisconsin by Monday morning along with a weak surface reflection. We'll probably see some showers and a few storms move over the lake and affect the northwest cwa by Monday and afternoon with some of the convection eventually drifting east Monday night. There's decent instability...MUCAPE around 1500 j/kg Monday afternoon and shear values climb to around 35kts over the northwest cwa. So this area may be favored late Monday for a few stronger storms.

A stronger short wave and surface low will emerge from the Plains Tuesday and push a warm front through mid day Tuesday followed by a cold front Tuesday evening. Bulk shear increases during the day Tuesday and given the warm front moving through, spinups are a concern. Dynamics are a bit stronger Tuesday night. However, instability may be a bit weaker given the lack of heating. That said, the models do show a mid level speed max around 65kts moving across the cwa 06z Wednesday in conjunction with a 60 kt LLJ. The evolution of this system bears watching.

Precipitation may linger through Wednesday as the upper low slowly moves east. Overall, the Monday-Wednesday timeframe may be rather wet with QPF in the 1-2 inch range.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
Issued at 124 PM EDT Sat May 18 2024

There is only one minor noteworthy event in the forecast period through 18z. That is a frontal passage overnight into the Sunday morning hours.

We currently have cumulus development with the boundary layer moisture left from this morning that is lifting up. We expect that this moisture will mix out this afternoon. These clouds are VFR, and should remain that way until sunset when they diminish.

We will see a frontal boundary start to move through overnight, and exit the area Sunday morning. At this time, it looks like a period of 5-7k ft clouds will accompany this, with a few sprinkles expected. Behind the front, clouds will scatter out a bit and winds will turn to become from the NW. Some diurnal cumulus can be expected once again.

MARINE
Issued at 333 AM EDT Sat May 18 2024

Patchy sporadic marine fog has been noted overnight and conditions are conducive for more of it to develop this morning. Therefore the marine dense fog advisory remains in effect through midday.
Otherwise winds and waves will stay well below Small Craft Advisory levels this weekend.

GRR WATCHES/WARNINGS/ADVISORIES
MI...Air Quality Alert until midnight EDT tonight for MIZ050-056-057- 064-071.
MARINE...None.

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