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LCZ460 Lake St Clair- 355 Am Est Wed Dec 6 2023
Today..Northwest winds 10 to 15 knots becoming west 5 to 10 knots in the afternoon. Partly Sunny. Waves 2 feet or less.
Tonight..West winds 5 to 10 knots becoming southwest 15 to 20 knots. Mostly cloudy. Waves 2 feet or less.
Thursday..Southwest winds 15 to 20 knots diminishing to 10 to 15 knots early in the afternoon. Partly Sunny. Waves 1 to 3 feet.
Thursday night..South winds 10 to 15 knots increasing to 15 to 20 knots after midnight. Partly cloudy. Waves 1 to 3 feet.
Friday..South winds 15 to 20 knots. Mostly Sunny becoming partly Sunny in the afternoon becoming mostly cloudy. Waves 1 to 3 feet.
Saturday..South winds 15 to 20 knots. Mostly cloudy with light showers likely. Waves 1 to 3 feet.
Sunday..Northwest winds 15 to 20 knots with gusts to 30 knots. Light showers. Waves 2 to 4 feet. A small craft advisory may be needed.

LCZ400
No data

FXUS63 KDTX 061410 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 910 AM EST Wed Dec 6 2023

UPDATE

Passage of a shortwave has released lake moisture inland across SE MI which has resulted in widely scattered snow showers focused along and west of I-75. Radar is sampling snow shower depths up to 7 kft with sporadic sampling to 30dbz, so some minor accumulation of a few tenthsof an inch will be possible, hampered by the more transient nature of the activity. Snow showers chances will persist leading into the afternoon.

For the afternoon and evening, low-level flow will back from northwest to west which will release additional Lake Michigan moisture inland. This will bring the low chance for flurries mixed in with some drizzle. No accumulation will come from any afternoon precipitation with highs pushing into the upper 30s.

PREV DISCUSSION
Issued at 633 AM EST Wed Dec 6 2023

AVIATION...

A shortwave that is tracking southeastward through Southeast Michigan is causing lake effect snow activity to release and advect downstream of Lake Michigan. An area of virga, flurries, and sporadic snow showers is now advancing into the northwest part of the forecast area. The activity is expected to remain very low in coverage. Low VFR and potentially MVFR will overspread the region later this morning, then expected to scatter this evening before a high cloud veil arrives. Increasing gradient flow with strengthening low level jet is expected to bring southwest winds of 10 to 20 knots tonight.

DTW THRESHOLD PROBABILITIES...

* High for ceiling 5000 feet or less this afternoon.

PREV DISCUSSION...
Issued at 353 AM EST Wed Dec 6 2023

DISCUSSION...

Starting the morning off in a transition region between the lingering surface trough exiting to the east and high pressure sprawling across the Plains. This high will drift southeast through the day with southern MI on the northern periphery of it. There is plenty of low level moisture between these systems as noted by the wealth of stratus all across the Great Lakes especially in the wake of the lakes. Though it is not completely overcast as there are also several pockets of clearings within this region, especially over SE MI. As this pattern shifts southeasterly today, winds will flip from northwesterly to westerly which will give the moisture on the west side of the state a push eastward through SE MI. There are some obs reporting light rain which pairs well with regional satellite, so question is...what happens when this plume passes over SE MI today? Most likely we'll go overcast for a while but there is a chance we could squeeze out some drizzle as the moisture is below the DGZ and surface temps are reaching into the upper 30s. As this shouldn't be impactful and is low confidence to occur, will leave out of the forecast at this point and see how well we saturate with the morning sounding and satellite trends before adding to the forecast.

The upper levels offer the next chance of precip, mainly for Mid MI and the northern Thumb as a short wave tracks through the developing northwest flow. The longwave ridge over the the western and central conus will be sliding eastward while this low amplitude shortwave rounds the ridge and tracks across Lake Huron tonight. Narrow corridor of fgen along the pv filament will largely stay over northern lower and Lake Huron, but there is a signal for a band of low level convergence off the lake to get pushed through mid MI and the Thumb which could be enough to spark a few light showers as the low level jet passes overhead. Moisture quality with the warm advection is questionable once again with some degree of saturation up to around 7kft, but that becomes nearly isothermal around -5C which won't be enough for snowflakes. So hedged overnight chance pops to a rain/snow mix but QPF looks to be a trace anyway so only impact would be a glaze on roads if temps drop quickly to below 32.

Fairly quiet for the end of the week Thursday and Friday as the ridge axis passes overhead opening the door for deep southwesterly flow and warm air advection. 850mb temps rise to around 7C which has led to highs forecast in the upper 40s to around 50 with partly cloudy skies. Meanwhile, a strong trough is getting carved out over the western conus with a 140 knot jet streak helping strengthen it further while it advances across the Plains. The original mid level and surface lows will be located up over western Ontario with a long cold front then extending south to Texas. Won't get overly detailed at this point, but models have been pretty consistent with advertising a mid level shortwave exciting a surface low along the front which would track north through the Midwest Saturday. this keeps the warm sector over SE MI resulting in warm temps again but moisture advection along the front from the Gulf with a trough pivoting to a negative tilt and a very dynamic upper level trough and jet looks to produce a round of rain showers, and possibly thunderstorms, across lower MI Saturday into Saturday night. Though its early, the trend over the last couple days has been a westward shift adding confidence to the warm solutions, but there are a few days left this week where additional shifts are likely/possible.

Sunday is in question as to how fast the surface front sweeps through leading to low confident high temps. A surge of cold air digging southeast will race in for the afternoon while lingering wrap around moisture and upper level trough keep precip chances around. 850mb temps dropping to around -10C or lower (per ECMWF)
would lead to a changeover to snow.

MARINE...

High pressure builds in today, maintaining light winds that gradually back to the southwest as the surface ridge axis slides overhead and a warm front lifts through the region. A weak low then clips northern Lake Huron overnight, supporting a period of wet snow for mainly the open waters before exiting into Ontario by mid-day Thursday. Will see some constriction to the pressure field as this system glances through, which further organizes and strengthens the southwest gradient Thursday. Standard concerns for the Saginaw Bay channel to see elevated wave heights in the SW flow regime, thus Small Craft Advisories are in effect from the Bay to Harbor Beach.
Southerly winds ramp up again on Friday as strong low pressure develops upstream. This system brings potential for heavy precipitation, initially as rain Saturday with a possible transition to snow Sunday/Monday dependent on the low track. Early indications suggest a tight gradient on the backside of the low and a much colder airmass, so this will be a window to watch for potential gales Sunday-Monday.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory from 10 PM this evening to 4 PM EST Thursday for LHZ421-441.

Small Craft Advisory from 10 PM this evening to 10 AM EST Thursday for LHZ422.

Lake St Clair...None.
Michigan waters of Lake Erie...None.

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