Sunrise 6:26 AM   Sunset 8:43 PM Moonrise 12:00 AM   Moonset 7:11 AM

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LHZ345 Straits Of Mackinac Within 5 Nm Of Mackinac Bridge Including Mackinac Island- 433 Am Edt Sat Apr 27 2024
.small craft advisory in effect through late tonight - .
Today - Southeast wind 10 to 20 knots with gusts to 25 knots becoming southwest in the afternoon. Chance of showers and slight chance of Thunderstorms in the morning. Waves 2 to 4 feet. Tonight - West wind 15 to 20 knots. Scattered showers and Thunderstorms. Waves 2 to 4 feet. Sunday - North wind 10 to 15 knots. Rain showers likely. Waves 2 feet or less. Sunday night - East wind 15 to 25 knots with gusts to around 35 knots. Rain showers. Waves 3 to 5 feet.
winds and waves higher in the vicinity of Thunderstorms.
see the open lakes forecast for days 3 through 5.

LHZ300
No data

FXUS63 KAPX 270827 AFDAPX

Area Forecast Discussion National Weather Service Gaylord MI 427 AM EDT Sat Apr 27 2024

KEY MESSAGES

-- Showers/isolated thunderstorms this morning, ending before noon.

-- Scattered severe thunderstorms are possible this evening into tonight, bringing the chance for damaging winds, large hail, and a tornado or two.

-- Scattered showers with isolated thunderstorms Sunday into Monday.

-- Light rain showers Tuesday night into Wednesday.

SHORT TERM /THROUGH TONIGHT/
Pattern Synopsis:

Well defined shortwave trough currently over the Upper Midwest will continue to lift into the northern Great Lakes today, becoming more open with time as amplified ridging folds over New England. The associated surface cyclone will trek across the far northern Great Lakes and Ontario today, eventually working into Quebec later tonight. The attendant warm front will lift northward through the area this morning into early afternoon, as a cold front draped southwest from the system center looks to slide from northwest to southeast across northern Michigan this evening and tonight.

Forecast Details:

Showers/isolated thunder this morning -- Showers ongoing across parts of northern Michigan will continue through much of this morning, along with the potential for isolated embedded thunderstorms. This activity should end before noon, leading to a lull in shower/storm chances through the afternoon into the early evening hours. With this, morning cloud cover is expected to scatter out this afternoon, helping temperatures to warm into the low to mid 70s.

Scattered severe storms possible this evening into tonight -- Bottom line up front is that scattered severe thunderstorms will be possible this evening into tonight, primarily across northern lower Michigan between 6PM and 2AM. All severe hazards will be possible with any strong storms that form later today, including damaging winds, large hail, and the potential for a few tornadoes. With a complicated forecast involving high uncertainty -- relatively low confidence in strong storms, but any strong storms will carry the potential to produce tornadoes -- will expand on the details of these uncertainties below:

1.) Will strong storms form? (forcing, instability, and capping) -- This is perhaps the biggest question at this time. Current confidence is that storms will develop in the 6PM - 9PM timeframe along/ahead of the cold front. However, competing factors will be at play. From the synoptic perspective, activity later today may actually be fighting weak subsidence aloft - which will work against strong storms attempting to develop.

To oddly add, a bit of a "Goldilocks" scenario may need to come together to maximize severe potential later today. Ample buoyancy in terms of severe parameters should be in place this evening (~1,500 J/kg MLCAPE) to support strong storms. However, too strong of advection aloft to bring steeper lapse rates (increasing instability) may also end up preventing strong storms from forming due to a stronger capping inversion. If cloud cover clears and we warm more aggressively than anticipated, this could decrease favorable moisture within the boundary layer and potentially prevent stronger storms from forming. Thus, a delicate balance of sufficient moist boundary layer depth and instability aloft may be necessary for severe storms. Current thoughts lean towards a more favorable environment in place later today at this time.

2.) How strong may storms be? -- While there is relatively high uncertainty in strong storms forming later today, any strong storm will be capable of producing damaging winds, large hail, and tornadoes. Strong deep-layer shear (~45-50 kts) will overlap with aforementioned instability to support potential for organized strong storms. Southwest winds veering and strengthening quickly off the surface will create plenty of low-level streamwise vorticity with looping hodographs and ~250-300 effective SRH to support a tornado threat with any multicell clusters/embedded supercells. While there will be a strong component of boundary-parallel flow that typically tends to keep convection in the zone of forcing and promote a linear storm mode, relatively slow initial frontal movement may be enough to help keep any strong storms semi-discrete in nature for a short window during the evening -- increasing severe potential for a period of time. To note, convection-allowing models tend to struggle across the Great Lakes in scenarios like this. While most output may seem unimpressive at first look, a supportive environment for all severe hazards will be in place later today and will still be monitored closely -- despite what some current/future model forecast reflectivity suggests. Be sure to stay tuned to the latest forecast for updates, especially later today as the severe risk will linger into the overnight hours.

LONG TERM /SUNDAY THROUGH FRIDAY/
Pattern Synopsis and Forecast:

Southwest flow aloft will remain on Sunday. Spokes of energy swing through during the day and into the overnight hours resulting in scattered rain showers and perhaps some embedded thunder, especially overnight. Warm front lifts through northern Michigan on into Monday as low pressure system moves into the Upper Midwest resulting in continued shower and some possible storm development. Frontal boundary with drier airmass will follow Monday night as low pressure system moves northeastward. Another low pressure system will move well to the north of the area with another shot at showers or storms in the Tuesday night to Wednesday time frame as the associated sfc boundary passes through. Looks messy and potentially unsettled thereafter late next week.

Primary Forecast Concerns:

Energy aloft will rotate through northern Michigan within southwest flow Sunday and Sunday night. Thus, a couple rounds of scattered showers with a few embedded thunderstorms will be possible (albeit most of the instability looks to remain south of our area). Although showers are likely Monday morning, mid to upper 50s dewpoints and 70s sfc temps during the afternoon will likely foster at least a little instability. That being said, mid level lapse rates are quite poor as there will be warmer air in the mid levels of the atmosphere. Thus, thunderstorms will be possible during the afternoon hrs Monday. Any organized threat does appear limited though for the aforementioned reasons (I suppose still worth keeping an eye on). Sfc boundary will move through Monday night putting an end to precipitation by Tuesday morning as drier air works into the region.

Next period in time to monitor will be Tuesday night into Wednesday.
Upper level low will move from the Northern Plains into Canada Tuesday evening into Wednesday with an associated sfc low following suit. Sfc boundary associated with this feature will move from the MN-WI into Michigan Tuesday night into Wednesday potentially focusing some shower development. There did appear to be some minor instability on Wednesday via the previous guidance, but the latest suggests very little. Thus, for right now calling it a chance for showers (some of the guidance is diminishing shower threat as it approaches the area, will have to see if that holds true) but really does not appear too terribly impactful unless the thermodynamic environment/precipitation coverage improves. Temperatures remain mild through mid week. Looks to be a lot of energy and moisture hanging around the center of the country in the extended, thus could more rain chances to end the week.

AVIATION /06Z TAFS THROUGH 06Z SUNDAY/
Deep low pressure will lift NE out of the Central Plains and into the Upper Mississippi Valley overnight...thru Lake Superior on Saturday...reaching James Bay by Saturday night.
Deep moisture will surge northward ahead of this system...
generating waves of showers and embedded thunderstorms across all of the Western Great Lakes region over the next 24 hours.
Cigs will gradually drop to low VFR/MVFR overnight into Saturday as showers and storms develop across our area. LLWS will develop late tonight into early Saturday as low level winds strengthen in advance of this system. Surface winds will remain from the SE at 15 to 25 kts overnight...shifting to the south and eventually SW on Saturday and further strengthening to 20 to 30 kts.

APX WATCHES/WARNINGS/ADVISORIES
MI...None.
MARINE...Small Craft Advisory until 2 AM EDT Sunday for LHZ345>349.
Small Craft Advisory until 2 AM EDT Sunday for LMZ323-341-342- 344>346.
Small Craft Advisory until 2 AM EDT Sunday for LSZ321-322.

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