Sunrise 6:43 AM   Sunset 8:41 PM Moonrise 11:02 PM   Moonset 6:52 AM

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LMZ845 South Haven To Holland Mi- 1105 Am Edt Fri Apr 26 2024
Rest of today - Southeast winds 15 to 20 knots. Mostly Sunny through early afternoon then becoming mostly cloudy. A chance of rain showers in the afternoon. Waves 1 to 2 feet. Tonight - Southeast winds 20 to 25 knots. Rain showers and a chance of Thunderstorms. Waves 2 to 4 feet.Saturday - South winds to 30 knots. Partly Sunny with a chance of showers and Thunderstorms. Waves 3 to 5 feet. Saturday night - Southwest winds 15 to 25 knots. Partly cloudy with a chance of showers and Thunderstorms. Waves 3 to 5 feet. Sunday - South winds 15 to 20 knots. Rain showers likely and a chance of Thunderstorms. Waves 2 to 3 feet. Monday - South winds 20 to 25 knots. Rain showers likely and a chance of Thunderstorms. Waves 2 to 4 feet. Tuesday - Southwest winds around 15 knots. Mostly Sunny. Waves 1 to 3 feet.

LMZ800
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FXUS63 KGRR 261743 AFDGRR

Area Forecast Discussion National Weather Service Grand Rapids MI 143 PM EDT Fri Apr 26 2024

KEY MESSAGES

- Occasional showers and storms tonight through Monday

- Briefly Dry Tuesday, then Additional Showers Wednesday/Thursday

UPDATE
Issued at 1045 AM EDT Fri Apr 26 2024

Nothing to really update for the forecast this morning. We will see elevated Fire Weather conditions through much of the day with a dry air mass in place/drier air mixing down, and somewhat gusty winds developing. With the recent rain earlier this week however, conditions should not get out of hand.

The aforementioned dry air will delay rain showers moving in later today a bit at the onset. There does look like a small chance of a few will arrive for the SW corner of the area prior to the end of this forecast period. Thunder does not look possible until we approach midnight, and thereafter.

DISCUSSION
Issued at 353 AM EDT Fri Apr 26 2024

- Occasional showers and storms tonight through Monday

A ridge aloft will slide eastward today and allow a weakening upper shortwave to move into Minnesota tonight. At the surface a warm front will move into the area tonight. Surface dew points tonight will surge into the 50s tonight with MUCAPE values increasing to around 500 j/kg late. Today will mainly be dry with a lowering and thickening cloud base ahead of the warm front.
Tonight, showers and a few storms are expected as the instability increases overnight. Not expecting any strong storms given the lack of instability associated with the nocturnal minimum.

Saturday we will be in the warm sector of the system as it weakens and moves into Canada off to our north and west. We are in the day 2 SPC outlook with a slight risk for areas to the north and west of Grand Rapids. We certainly could see some warm sector convection on Saturday, but this looks to be scattered and relatively low chance. What convect we do see in the day 2 period would likely come Saturday night as upstream storms and the associated cold front sag in from the northwest. Given bulk shear Saturday night is near 40 knots over Central Lower and MUCAPE values will be in excess of 1,000 j/kg cannot disagree with a threat of some severe weather, but overall feel our chances are not great. Main factors that would lead away from severe weather Saturday night are a low level jet that is forecast to weakening as is the system to the west. We will obviously be monitoring for severe weather both Saturday afternoon and night, but feeling is it may not be a slam dunk event.

Chances for showers and storms continue Sunday into Monday as another plains upper shortwave works northward into Canada. We will again be downstream of the better activity most likely but the warm and showery weather will continue. Best chances in this time frame will likely be Sunday afternoon on the warm front across Central Lower Michigan. Day 3 only has us in general thunder from SPC and cannot argue with that.

Highest rainfall totals from this weekend into early next week will be west of Lake Michigan where the deeper moisture and more importantly stronger dynamics will be in play. We are still looking at solid rain in our area though through Monday night however on the order of 0.50 inches towards Jackson to 1.50 inches up near Ludington. If we see any hydro issues at all it will likely be to the north of the Grand River basin up along the Muskegon and Pere Marquette. Given the totals we are forecasting though over multiple days we think the rivers will be able to handle it.

- Briefly Dry Tuesday, then Additional Showers Wednesday/Thursday

A break in precipitation is expected Tuesday as brief weak ridging moves in place. Conditions turn active with showers Wednesday and Thursday as a cold front associated with an upper shortwave dives into the region. An 850mb thermal trough falls into the region late in the week leading to cooler temperatures starting Thursday. Summer- like temps in the 70s through the first half of next week will fall into the low 60s Thursday and Friday.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
Issued at 142 PM EDT Fri Apr 26 2024

A warm front to our south today will move through tonight causing cigs to fall from VFR to MVFR levels from 05-08z. However, some uncertainty to the exact timing of MVFR cig development is expected due to complications of low-level dry air and how long that takes to erode. Rain showers will also move in after 00z leading to occasional MVFR visibilities as well. A few embedded thunderstorms are possible mainly for sites MKG, AZO, GRR, and BTL, where better instability intersects shower activity. Have included PROB30 for thunder for these sites for the move favorable window of TSRA. Widespread rain showers will end from west to east between 12-15z and while isolated showers and storms are possible behind the main grouping confidence is to low to include in the TAFs.

The other notable concern is wind. Southeast winds of 10-20 knots gusting to 25 knots will turn southerly overnight. A strong low- level jet also moves in after 00z meaning TAF sites approach LLWS criteria even outside of convection. Given the borderline conditions given already elevated surface winds will let the next aviation forecaster make the call on inclusion of LLWS when surface observations show how far winds fall this evening.

MARINE
Issued at 353 AM EDT Fri Apr 26 2024

Will hold off on any marine headlines with this morning's forecast package. That said, we may need marine headlines as we head into Saturday in strong southerly flow. Strong warm air advection this time of year though is always troublesome given the inversion that develops. Strongest winds will flow over the cold dome near the surface and never make it down to build waves. Today, winds are offshore (southeast) and more in the 10-20 knot range. Winds tonight will begin to ramp up and we could need a headline for winds alone, but given short fetch (southeast/off shore) and mixing to the surface concerns will hold off. NAM 3km Bufkit winds are suggesting solid SCA conditions on Saturday if not Gales. We will hold off for now and take another look today at any potential headlines. A prolonged period of stronger south winds will exist from Saturday right through the day on Monday. Feeling is at least some of this will struggle to make it to the surface. Areas of fog may also be an issue Saturday-Monday as higher dew point air will be advected out over colder water which is usually a set up for instant fog on the Great Lakes in the spring of the year.

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

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