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LHZ443 Port Sanilac To Port Huron Mi- 339 Am Est Wed Nov 29 2023
.small craft advisory in effect through this afternoon...
Today..Southwest winds 20 to 25 knots with gusts to 30 knots diminishing to 15 to 20 knots in the afternoon. Mostly cloudy. A slight chance of light snow showers in the morning. Waves 2 to 4 feet subsiding to 1 to 3 feet late in the afternoon.
Tonight..Southwest winds 15 to 20 knots. Mostly cloudy. Waves 1 to 3 feet.
Thursday..Southwest winds 15 to 20 knots increasing to 20 to 25 knots with gusts to 30 knots in the late morning and afternoon. Mostly cloudy. Waves 3 to 5 feet. Waves occasionally around 7 feet.
Thursday night..Southwest winds 15 to 20 knots becoming west 10 to 15 knots in the late evening and early morning, then becoming northwest 5 to 10 knots after midnight. Mostly cloudy with a chance of showers. Waves 2 to 4 feet subsiding to 2 feet or less in the late evening and overnight.
see lake huron open lake forecast for days 3 through 5.

LHZ400
No data

FXUS63 KDTX 290845 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 345 AM EST Wed Nov 29 2023

DISCUSSION

As of 08Z, radar mosaic highlights a large precipitation shield that expands from northern lower Michigan through western Ontario.
Precipitation will attempt to expand into the northern fringes of the cwa leading into the late morning hours, just downstream of a compact shortwave. While the bulk of snow showers are expected to hold across Lake Huron, portions of the northern Thumb and northern Tri-Cities will be susceptible to the southern edge of the precipitation shield. Any snowfall observed would be very light with accumulations totals holding to or below a half-inch. Otherwise, very cold conditions to start the morning as temperatures reside in the upper teens to lower 20s. Wind chills have dropped into the single digits.

The thermal trough that was responsible for winter weather over the past several days will exit the Great Lakes today as upper-level flow starts to exhibit a little more zonality. This will bring a couple days of of dry weather and warming temperature trends. The 00Z DTX RAOB sampled 850mb temperatures down to an impressive -18C last evening, but model projections showcase swift low-level warming to -2C by 00Z tonight, with a little more moderation to 2C by 00Z Fri. This waa will extend through the surface allowing daytime highs to peak in the mid-30s today and to normal/slightly above normal temperatures Thursday with highs in the 40s, making a run towards 50 near the MI/OH border. Expect the continuation of some breezy conditions during daylight hours with the modest mixing depths to 2kft pulling down gusts around 20-25 mph today, increasing to 25-30 mph tomorrow once a stronger llj builds over the state.

Precipitation is expected across portions of the cwa on Friday, derived from an upper-level wave that now resides just offshore of California. This wave is projected to drive south and move onshore around the Baja region later this afternoon, moving south of the Four Corners region by Thursday morning and will start to turn northeast early Friday morning once it approaching Ark-La-Tex.
Shortly after this point, system relative isentropic ascent quickly commences first across the Ohio Valley into Southern Michigan starting between 00Z to 12Z Fri and then expands north through 18Z.
At this time there is extremely strong convergence that precipitation will clip the southern portion of the cwa, but the highest uncertainty at this point is how far north the precipitation shield expands north through the day on Friday. The NBM 10th percentile for measurable QPF expands up through I-94 by 00Z Sat, showcasing the strong convergence with most model output, but the 50th percentile still leaves the northern Tri-Cities and northern Thumb dry, owing to the uncertainty. The outgoing forecast will have definitive PoPs (near 100%) towards the border with a gradient down to chance PoPs (30%) across the Tri-Cities and northern Thumb until additional convergence is noted.

P-Type will also potentially be a big challenge, conditional on a couple of factors. First, how far north the precipitation/warm air advection expands. Any initial precipitation looks to start as all rain, but several deterministic models e.g. ECMWF/GFS have a brief but impressive window of dynamical cooling that offsets surface warming. This would lower the temperature of the column/freezing level just enough to afford a window for the transition from rain to snow. Most of this would fall during daylight hours with surface temperatures just above freezing which could hamper snow accumulation potential. As a preliminary analysis, the potential for 1+ inch of snow accumulation would likely be confined just north of I-94 across the glacial ridge/Irish Hills, where precipitation rates are maximized and the column is just cold enough to support snow with the better precip rates. But again with many moving parts, it is too soon to dive into specifics, but it is certainly worth noting at this time. It is looking increasingly likely that a secondary trailing wave will follow the initial wave and will move over or clip portions of SE MI late Friday night into Saturday morning, and with a more ideal overnight time window, accumulating snow would again be a possibility.

Meridional shortwave flow Sunday into the early week period brings several additional periods for precipitation. Temperature highs will be around normal in the upper 30s to lower 40s and lows around the freezing mark through the early week period. Overall after a couple days of dry weather, expect an active weather pattern to return which include a low end possibility for accumulating snow Friday and Saturday.

MARINE

Southwest winds remain elevated through this morning with the increased pressure gradient between the high pressure to the south and the clipper system swinging through the Great Lakes. Small Craft Advisories are in effect into this afternoon for Saginaw Bay and the nearshore zones of the Thumb. There is a potential for a brief period of gales during the morning hours across central and southern zones of Lake Huron. The brevity of gales precludes any headline issuance. This clipper system is also bringing an uptick in snow showers, mainly across Lake Huron. Unsettled weather conditions will continue into the later part of the week after a brief period of mild air or the region. Cold air moves in again leading to an uptick in wind gusts to around 30 knots again on Thursday afternoon and evening. A low pressure system lifts into the Ohio River Valley Friday into Saturday bringing another round of precipitation chances with wind gust potential topping out generally around 20 knots.

PREV DISCUSSION
Issued at 1040 PM EST Tue Nov 28 2023

AVIATION...

An ongoing backing of the low level wind fields to the southwest is a result of an upper level short wave and associated sfc trough advancing toward Lake Superior. This is causing the Lake Michigan strato cu field to shift north, with the back edge of these low end VFR cloud bases likely lifting north of FNT around 06Z. The short wave will track across the region early Wednesday, providing some light snow to mbS. Farther south, drier air will limit the snow potential and will likely keep cloud bases VFR. An increasing SW gradient will support frequent gusts over 20 knots on Wednesday. The low level flow will then veer more westerly Wed afternoon/evening.
This and a lowering inversion will increase the chances for MVFR based clouds later in the day.

For DTW...Southwest winds will increase during the course of the morning, with model soundings suggesting wind gusts over 20 knots are highly probable. The passage of the short wave late Wed morning will increase probabilities for sub 5000 foot cloud bases after 14Z.

DTW THRESHOLD PROBABILITIES...

* Low in ceilings below 5000 feet overnight and Wed morning.
Moderate Wed afternoon and evening.



DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EST this afternoon for LHZ421-422- 441>443.

Lake St Clair...Small Craft Advisory until 4 PM EST this afternoon for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 4 PM EST this afternoon for LEZ444.

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