Marine Forecasts

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7 Day Forecast for Marine Location Near Lexington, MI

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Area Discussion for - Detroit/Pontiac, MI

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FXUS63 KDTX 251807 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 107 PM EST Mon Jan 25 2021

AVIATION.

CIGS largely low VFR today heading into the snow event starting tonight. There are some scattered clouds around 1500ft showing up currently likely a result of northeast flow bringing in lower level moisture but as daytime mixing advances will expect those to scour out over the next hour or so. A system tracking eastward across the Ohio Valley tonight into Tuesday will then spread IFR clouds and snow showers northward through all the terminal sites. Snow will begin across the Detroit area around 06Z, reaching mbS closer to 12Z. Some indications of a period of LIFR CIGS/VSBYS within the heaviest snow that will occur around 10-15Z for Detroit, lagging slightly later northward. Light snow will then persist through the remainder of the day for all locations. One trend has been for drier mid levels to lift into far southern MI which could change snow to a mix of snow and freezing drizzle for a few hours. Will leave out of the forecast at this point while keeping a close eye on trends this evening.

For DTW . Will give lake induced MVFR clouds a chance to scour out with daytime mixing as obs are currently quite sporadic. Much attention remains on snow moving in tonight through Tuesday. Should start around 06Z, with heaviest snow likely between 10-15Z. Light snow lingering through the rest of Tuesday. Snow will be wet as it may transition to short period of freezing drizzle during the morning hours but will hold off on including in tafs at the moment as confidence is low.

DTW THRESHOLD PROBABILITIES .

* High for ceiling below 5000 feet today and tonight.

* High for ptype of snow tonight through Tuesday.

* Low for ptype switching to freezing drizzle Tuesday morning.

* Low for ceilings or visibilities to drop below 200ft or 1/2SM respectively.

PREV DISCUSSION. Issued at 338 AM EST Mon Jan 25 2021

DISCUSSION .

Conditions across Se Mi will remain dry through the daylight hours today as subtle mid level height rises and neutral to slightly anticyclonic low level flow expand across the northern Great Lakes region. Some breaks in the stratus overnight led to some fog development across Se Mi. Some of these breaks in the low clouds will persist through the morning. Mid and high level clouds will however increase during the afternoon in advance of the next system. With limited thermal advection and increasing cloud cover today, high temps will be limited to around 30.

An upper low will emerge in the lee of Rockies this morning and push across Kansas this afternoon. There is a well defined low level warm front associated with this feature extending into the Lower Tn Valley. Water vapor imagery shows a plume of tropical moisture of Pacific origin feeding into this frontal system. The low level warm front will be driven northward into the Ohio Valley today. Tonight, the upper low will translate from Kansas into Iowa. Low level flow across the Ohio Valley will actually target the Upper Ohio Valley/central Appalachians with the higher moisture and instability, with mid level dry air advecting into the northern Ohio Valley in its wake. Deep layer frontal dynamics will still however lift into srn Mi during the course of the night. There has been a notable trend toward a later timing of bringing the frontal forcing into Se Mi, with precip not expected to lift north of the OH/MI state line until late this evening.

Model cross sections still indicate decent moisture content being driven up the frontal slope across Srn Mi tonight, with 3 to 4 g/kg specific humidities advecting into the mid levels. Decreasing static stability aloft will provide the potential for a robust response within the mid level fgen as it advances northward across Se Mi tonight into Tues morning. One item of concern is the trend toward a more aggressive region of mid level dry air nudging into at least the srn portions of the forecast area late tonight, perhaps transitioning the snow to some freezing drizzle and limiting overall snow totals. The previous shift also noted that the better ascent occurs within a warmer thermal profile (-5 to -8C) which will keep snow liquid ratios relatively low (8-11 to 1). The upper low is still forecast to shear as it slides across srn Mi late Tues/Tues night. Current forecast trends do indicate the mid level frontal forcing weakening/shearing apart on Tuesday as the wave dampens. The lingering forcing may however be enough to grind out some lingering snow through the day Tuesday. Moisture depth will also improve with the passage of the wave Tues. There has been a slower trend on the departure of this system, enough so that there looks to be a little colder airmass across Lake Huron late Tues/Tues night. This may allow some enhancement off the lake across the Saginaw Valley and thumb region as the flow backs from northeast to north.

So in short, recent trends have been toward delaying the onset of precip until later evening. There has also been a trend toward holding the more persistent frontal forcing and better moisture depth across the north half of the forecast area late tonight through Tuesday. There is still some variations among ensemble members with respect to total qpf (with values ranging from 15 up to .45 inches). Suspect handling of the mid level dry air is playing into these differences. Given the recent trends, total forecast snowfall amounts of 2-4 inches tonight thru Tues will be shifted farther north, with a slight downward adjustment made for locals south of the I-94 corridor. Given the later start time and with still some forecast uncertainty, preference will be to hold off on any headline issuances attm.

There remains good model agreement for the latter half of the week with respect to Lower Mi remaining between a southern stream wave to the south and a compact upper low to the nortth/northeast of Lake Huron. The result will be dry and seasonally cold conditions Wed thru Fri.

MARINE .

Northeast winds will be on the increase today, as low pressure moves into the Ohio Valley this evening. Winds gusts will reach aob 25 knots over Western Lake Erie, and with the longer fetch, expecting some 4 foot waves to brush the nearshore zone. As the low continues north, northeast winds over Lake Huron will also likely reach aoa 25 knots tonight into Tuesday, especially over Saginaw Bay where the fetch is maximized. The prolonged onshore flow should lead to waves aoa 4 feet impacting the nearshore waters, and small craft advisories have already been issued, with the exception of inner Saginaw bay due to ice cover. In addition to the increased wind and waves, snow will overspread the region from south to north Monday evening into Tuesday, with visibilities reaching 1 mile or less at times.

Northeast winds look to persist even into Wednesday, but expected to be aob 15 knots during the day, before increasing Wednesday night as rapidly deepening low pressure exits the southeastern United States and moves off the Coast. Thus, small craft advisory may need to be reissued or extended as waves look to remain elevated through the end of the work.

DTX WATCHES/WARNINGS/ADVISORIES. MI . NONE. Lake Huron . Small Craft Advisory from 9 PM this evening to 5 AM EST Wednesday for LHZ421-441>443.

Lake St Clair . NONE. Michigan waters of Lake Erie . Small Craft Advisory from 7 PM this evening to 10 AM EST Tuesday for LEZ444.



AVIATION . DRK DISCUSSION . SC MARINE . SF

You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.

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Weather Reporting Stations

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Stations	Dist	Age	Wind	Air Temp	Water Temp	Waves	Pressure	DewPt
PSCM4	27 mi	37 min	NNE 5.1 G 6	30°F			1035.6 hPa (-2.0)
MBRM4 - 9014090 - Mouth of the Black River, MI	33 mi	49 min		32°F			1016.8 hPa
HRBM4 - 9075014 - Harbor Beach, MI	47 mi	49 min	N 8 G 9.9	30°F	35°F		1017.2 hPa	21°F

Wind History for Fort Gratiot, MI

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Airport Reports

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Airport	Dist	Age	Wind kt	Visibility	Sky/Weather	Temp	DewPt	Humidity	Pressure
St Clair County International Airport, MI	39 mi	42 min	N 3	10.00 mi	Overcast	32°F	25°F	75%	1017.3 hPa

Link to 5 minute data for KPHN

Wind History from PHN (wind in knots)

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Tide / Current Tables for

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Tide / Current Tables for

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Weather Map

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NOTE: East coast views moved to GEOS-16. They are experimental and not well supported by NOAA so they may not be correct so be warned. This change required redoing a large amount of the GOES code. If the image you are expecting is not showing, please let me know. You may need to use the EDIT function to update your location.
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