Sunrise 6:12 AM   Sunset 9:10 PM Moonrise 6:35 PM   Moonset 3:57 AM

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LMZ847 Grand Haven To Whitehall Mi- 1105 Am Edt Tue May 21 2024
.small craft advisory in effect from 10 pm edt this evening through Wednesday evening - .
Rest of today - South winds 5 to 10 knots backing southeast 10 to 20 knots late in the day. Mostly Sunny. A slight chance of showers and Thunderstorms in the afternoon. Waves 1 to 2 feet. Tonight - Southeast winds 15 to 25 knots veering south to 30 knots after midnight. Rain showers likely and a chance of Thunderstorms. Waves 2 to 4 feet building to 6 to 8 feet after midnight. Wednesday - Southwest winds 15 to 25 knots. Mostly Sunny. Waves 6 to 8 feet. Wednesday night - Southwest winds 15 to 20 knots. Mostly clear. Waves 2 to 4 feet.Thursday - Southwest winds 10 to 15 knots. Sunny. Waves 1 to 3 feet. Friday - Southeast winds 10 to 15 knots veering south. Mostly Sunny. Waves around 1 foot. Saturday - South winds 15 to 20 knots veering west. Partly Sunny with a chance of showers and Thunderstorms. Waves 1 to 3 feet.

LMZ800
No data

FXUS63 KGRR 211124 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 724 AM EDT Tue May 21 2024

KEY MESSAGES

- Severe Storms Possible Late Tonight

- Dry for Wednesday and Thursday; Rain Chances Return Friday

- Rain Chances Linger Through the Holiday Weekend

DISCUSSION
Issued at 350 AM EDT Tue May 21 2024

- Severe Storms Possible Late Tonight

A rapidly amplifying shortwave ejects out of the Central Plains into the Great Lakes this afternoon through late tonight. In response, a surface low deepens as it moves into northern Wisconsin and the UP while a trailing cold front becomes the focus for thunderstorm development. A cluster of storms currently working through Nebraska and western Iowa will be the focal point to monitor throughout the day today. Starting off semi-discrete, these storms will organize and transition into an organized line of storms by the time they reach central Iowa and western Wisconsin.

Meanwhile across lower Michigan ahead of the storms, return flow moisture bumps dewpoints into the mid to upper 60s with afternoon highs peaking in the low to mid 80s. Diurnal cumulus may give way to a few showers or a stray thunderstorm ahead of the main line of storms late tonight. Hi-res cams are in good agreement on a midnight time of arrival of the main line of storms, and are also favoring a quick weakening trend into lower Michigan given the late hour and strong nocturnal limiting factors. The progression of SPC Enhanced in far western Michigan to Slight/Marginal Risk in central to eastern Michigan nicely depicts the weakening trend with eastward progression. Damaging wind will be the main hazard to monitor as the storm mode transitions into a well organized QLCS to our west and travels east towards lower Michigan.

The eastward advancing cold front will be the focal point for any additional convection Wednesday, but as the boundary becomes parallel to the mean flow convection will be very limited and mainly shunted off to our far southeast. Therefore the risk of storms has shifted southeastwards.

- Dry for Wednesday and Thursday; Rain Chances Return Friday

Sfc frontal boundary will settle south of MI for Wednesday night through Thursday night with a sfc high and drier air mass sliding through, yielding dry conditions during this time.

Current guidance indicates that the boundary lifts back north as a warm front on Friday afternoon and night as the next shortwave tracks across the nrn Plains into MN/WI. Pops returning as this occurs and this is faster than in previous model runs.

- Rain Chances Linger Through the Holiday Weekend

Depending on the timing of the Friday wave, its possible that Saturday ends up being a mostly dry (and cooler) day due to a period of subsidence behind it. Confidence is too low at this time though to advertise a dry start to the weekend and 20-40 pct pops will be maintained. It is possible that those rain chances end up being restricted top just the morning-time.

A zonal flow aloft is progged throughout the holiday weekend with frontal zone/baroclinicity still nearby. This pattern will result in continued chances of showers and possible storms although the timing and coverage of convective events remains low confidence. Upshot is for a continuation of daily 20-40 pops but the weekend will certainly not be a washout and temperatures will average near to slightly above normal.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/
Issued at 724 AM EDT Tue May 21 2024

Expect widespread LIFR conditions in fog and low stratus to start today, however that will mix out by mid morning leaving VFR weather for the remainder of the day into this evening. Models are similar in showing a north-south oriented line of strong to severe storms coming onshore at MKG around Midnight tonight then moving east from there overnight. Wind gusts in excess of 40 kts will be possible with this line. Preceding the line, southerly winds will increase substantially after 02Z tonight with LLWS becoming likely.

MARINE
Issued at 350 AM EDT Tue May 21 2024

Winds stay mainly offshore today, then will shift southwesterly this evening while building. Strong to severe thunderstorms will move through the region late tonight resulting in locally strong winds and choppy waves in the vicinity of storms. Apart from storms, conditons become hazardous to small craft late this evening as winds gust towards 20 to 30 knots through tomorrow morning. Meanwhile, waves will build late tonight through Wednesday morning, gradually subsiding from south to north Wednesday afternoon.

GRR WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory from 10 PM this evening to 8 PM EDT Wednesday for LMZ844>849.

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