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LHZ345 Straits Of Mackinac Within 5 Nm Of Mackinac Bridge Including Mackinac Island- 1117 Am Est Tue Nov 28 2023
.small craft advisory in effect through Wednesday morning...
Today..West wind 10 to 20 knots. Scattered snow showers in the late morning, then isolated snow showers in the afternoon. Waves 2 to 4 feet.
Tonight..Southwest wind 15 to 25 knots. Snow showers. Waves 4 to 6 feet.
Wednesday..West wind 15 to 25 knots. Chance of snow showers. Waves 3 to 5 feet.
Wednesday night..West wind 15 to 25 knots. Mostly cloudy. Waves 3 to 5 feet.
see the open lakes forecast for days 3 through 5.

LHZ300
No data

FXUS63 KAPX 281722 AFDAPX

Area Forecast Discussion National Weather Service Gaylord MI 1222 PM EST Tue Nov 28 2023

UPDATE
Issued at 911 AM EST Tue Nov 28 2023

Not much to change to inherited forecast. Fairly well organized lake bands continue to impact the snowbelt locations this morning.
Flow is decidedly northwest...bringing the best snows into northwest lower Michigan. Transit pockets of one inch per hour snowfall rates within these bands, no doubt resulting in at least a few inches of additional accumulations where bands have been most persistent.

Expect lake processes to significantly throttle back as we head through this afternoon with quickly backing winds, agressive drying through the boundary layer, and lowering convective cloud depths (all a result of impinging surface ridge axis). Still looking at few more inches under those most persistent bands before this downward trend begins. All headline end times will remain.

NEAR TERM
(Today through Tonight)
Issued at 421 AM EST Tue Nov 28 2023

Key Messages:

- Accumulating lake effect snow will continue across NW lower and the eastern U.P. today with medium to high chances (40 to 70+ percent) for an additional 4 inches for localized areas.

- A lull in snow intensity and coverage is expected later this afternoon and evening.

- Additional accumulating snow is anticipated tonight into Wednesday morning with medium to high chances (40-70+ percent) for another 2 inches of snow across NW lower and the eastern U.P.

Pattern Synopsis:

Deep troughing will continue to pivot across southeast Canada/Great Lakes region as an associated surface cyclone treks northeastward across Quebec today. An attendant weak front looks to sag from north to south across northern Michigan this morning, eventually being pushed eastward as low-level ridging temporarily slides overhead this afternoon and evening. A shortwave embedded in the main flow looks to dig across the upper Midwest and overhead tonight, providing sufficient forcing aloft to support a weak cyclone that will move into Ontario/Hudson Bay with a seconds front swinging into the Great Lakes by Wednesday morning.

Forecast Details:

As stated in the key messages, accumulating lake effect snow will continue across parts of NW lower and eastern upper Michigan this morning into this afternoon. Forecast soundings display a favorable environment to support moderate to heavy snowfall rates within lake effect bands into this morning -- which has already been seen tonight at KCIU with heavy snow and visibilities dropping to 1/4 mile or less for over an hour as a concentrated band set up over the site. Wind direction across eastern upper and parts of northwest lower are expected to turn slightly more northwesterly with time through this morning as aforementioned surface ridging works into the region.

With this said, strongest banding is expected to focus across Antrim and Kalkaska counties through this morning, bringing high chances (greater than 70 percent) for an additional 4 inches of snow into early afternoon -- and even low chances (10-40 percent) for localized areas to see an additional 8" or more. Other portions of NW lower are expected to see a few more inches of additional snowfall during that time, most likely across the typical northwest snowbelts of northern lower and eastern upper. Drops to a quarter mile visibility will be possible underneath strongest lake effect bands, and wind gusts of 15-25 mph may lead to some blowing and drifting at times this morning with dry snowfall (SLRs close to 20:1). The combination of drops in visibility and snow-covered roadways will lead to hazardous travel across parts of the area this morning.

After a lull in snow intensity and coverage this afternoon and evening, accumulating snow chances will return along/ahead of the aformentioned front tonight. Forecast soundings display an appreciable portion of the saturated low/mid-level profile collocated within the DGZ, which will likely lead to efficient snow crystal growth and thereby efficient snowfall. Medium-high chances (40-70 percent or greater) exist for an additional 2 inches across much of NW lower and eastern upper Michigan, with some areas near Little Traverse Bay most likely to see totals near 4 inches.

SHORT TERM
(Wednesday through Thursday)
Issued at 421 AM EST Tue Nov 28 2023

HIGH IMPACT WEATHER POTENTIAL: Low for now...periodic light snow and/or drizzle/freezing drizzle.

PATTERN SYNOPSIS/FORECAST:

Longwave troughing still holding steady over the eastern continent.
Positively tilted shortwave trough axis about to swing through the Upper Great Lakes as of 3z/28...as lake effect continues amid sub - 12C 850mb air crossing the region. Ridging remains firm over the western US...with strong northerly flow largely encompassing the central US/MS valley...deforming into a confluence zone over the SE US, where 160+kt zonal-ish upper level jet hangs on...keeping most of the moisture out of the CONUS. Clipper system trekking over the ridge into the central Canadian Prairies, with a surface reflection extending from Saskatchewan down into the Mid MS Valley; strong height rises on warm advection ahead of this feature over Manitoba into the Upper Midwest.

Shortwave trough axis exits eastward today...but height rises in its wake will be short-lived...as next clipper system rides the flow down into the Great Lakes tonight into Wednesday. Do think a surface boundary will swing through our area Wednesday morning...though it looks like the boundary will hang on back to the NW behind this...as additional energy digs into the western US. Suspect we may not be entirely quiet Wednesday night into Thursday...as this energy digs across Canada and develops a surface low to our north going into Thursday. Signals point toward the system crossing the region later Thursday into Thursday night, although there are still a few minor timing differences to contend with.

Primary Forecast Concerns: Periods of snow/freezing drizzle...

Main vort max should be on its way out Wednesday morning, though some energy lingering over the area should keep things active, particularly over the usual snowbelts. Mean cloud flow looks to shift from NW/WNW early toward more W by late in the day...with guidance currently pointing toward more favorable inversion heights (maybe 6kft) up across the EUP where there will be better fetch off southern Lake Superior...and think this is where the bulk of the snow will fall in the afternoon. Moisture stripping out further south over NW Lower suggests drizzle/freezing drizzle could become a concern, as inversion heights plummet and cloud top temperatures warm to -5C or so, diminishing ice nucleation potential.

Thursday could be a bit tricky...as guidance points toward potential for a lack of moisture early in the day, increasing with time as that system takes shape to our northwest...and as better forcing approaches. Think that W/SW flow areas would be more favored, with lower SLRs as the profile should be warmer...though again, can't rule out the freezing drizzle potential, either...particularly if this system ends up coming through when surface temps are below freezing (i.e., Thursday night). Main focus should again be the EUP closer to the system, though not impossible that parts of Northern Lower could be affected, particularly if the approaching southern stream system is able to give a boost to forcing...and if it is further north (which is more likely if the Thursday system zips through quicker).

LONG TERM
(Thursday night through Monday)
Issued at 421 AM EST Tue Nov 28 2023

HIGH IMPACT WEATHER POTENTIAL: Minimal for now...

PATTERN SYNOPSIS/FORECAST:

Aforementioned trough should be on its way out Friday, lingering a SW-NE oriented BCZ into the southern Plains, along which a southern stream disturbance looks to ride. Think the bulk of the impacts from this will be well south of our area, assuming the current idea holds...though it's not impossible that warm advection could bring some precip into our area...and will have to watch for lake convection in the meantime, with the northern stream trough nearby.
Not impossible there could be another weak disturbance Friday night...though the bigger story will be troughing digging over the western US going into the weekend. While this does signal potential for milder weather here in the Great Lakes...do think warm advection concerns will come into play as bits of energy eject northeastward along the flow toward the Upper Midwest this weekend. Still working on timing out these bits of energy for Sunday into Monday and beyond, though it appears the overall trough axis will slip overhead as we go into Monday night. Think it will remain at least nuisance-y active here in the Great Lakes into the start of next week...with potential for lake effect to return going into the end of the extended and beyond, depending on how long the upper trough hangs around
With the potential for milder air and warm advection
will be keeping an eye out for this active period to also be a little more mixy/rainy than what's going on out the window right now.

AVIATION
(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1218 PM EST Tue Nov 28 2023

Improving conditions as we head through the remainder of this afternoon and evening. Next round of lake enhanced snow arrives later tonight, gradually ending as we head through Wednesday morning. This will likely result in more MVFR to IFR conditions, with the worst conditions expected at those tafs locations near Lake Michigan. Likely to again see some mostly minor snow accumulations, although could be looking at several inches near KPLN. Gusty winds will result in some patchy blowing and drifting snow at times.

MARINE
Issued at 421 AM EST Tue Nov 28 2023

Small craft advisory winds and waves are expected to continue across northern Great Lakes nearshore waters through tonight.



APX WATCHES/WARNINGS/ADVISORIES
MI...Winter Weather Advisory until 1 PM EST this afternoon for MIZ021- 022-027-028-086-087-099.
LH...Small Craft Advisory until 7 AM EST Wednesday for LHZ345>349.
LM...Small Craft Advisory until 7 AM EST Wednesday for LMZ323-341-342- 344>346.
LS...Small Craft Advisory until 7 PM EST this evening for LSZ321-322.

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