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LCZ422 1134 Pm Edt Wed Sep 6 2023
a marine weather statement has been issued for the following areas...
nearshore and open waters from harbor beach to port huron mi... St. Clair river...
at 1134 pm edt, doppler radar indicated strong Thunderstorms, capable of producing winds to up 30 knots. These Thunderstorms were located along a line extending from 9 nm southwest of port sanilac to near lexington to near st. Clair, moving east at 30 knots.
strong Thunderstorms will be near, lexington and port huron around 1140 pm edt. Port sanilac around 1145 pm edt.
precautionary/preparedness actions...
mariners can expect gusty winds up to 30 knots, locally higher waves, and lightning strikes. Boaters should seek safe harbor immediately until these storms pass.
&&
lat...lon 4300 8242 4297 8241 4292 8246 4281 8248 4290 8251 4301 8247 4322 8256 4348 8261 4366 8214 4359 8212

LCZ400
No data

FXUS63 KDTX 031058 AFDDTX

Area Forecast Discussion National Weather Service Detroit/Pontiac MI 558 AM EST Sun Dec 3 2023


AVIATION

LIFR cigs/vsbys have expanded across the Detroit terminals this morning with easterly flow off the lakes enhancing the low level moisture already pretty saturated ahead of the approaching system.
LIFR cigs do spread across the rest of southern MI sites as well which will last the first several hours of the forecast. The low will track up through the area spreading rain across all sites from 12-22Z before pushing off to the east. Flow will flip around to the west which will bring in drier air behind the system, bringing slightly improving conditions tonight. mbS and FNT look to remain in the lingering surface trough heading through tonight which will keep wrap around moisture over those sites thus they will possibly hold on to IFR longer through the night. Precip type will be rain for all sites today with some hints of colder air working into the Saginaw Valley which may bring a few snowflakes later tonight.

For DTW...Sub mile vsbys and 200ft cigs should hold up til precip onset which still looks to be between 14Z and 16Z. This should help improve vsbys though cigs will remain LIFR through the afternoon til widespread precip ends around 22Z. Slow recovery of cigs expected tonight as drier air works into the region with northwesterly winds.

DTW THRESHOLD PROBABILITIES

* High in ceilings below 5000 feet today and tonight.

* High in precip type remaining as all rain on today.

* High for cigs/vsby to remain aob 200ft and or 1/2SM through 15Z.
Low the rest of the morning/afternoon.

PREV DISCUSSION
Issued at 303 AM EST Sun Dec 3 2023

DISCUSSION...

A phased upper level jet structure with favorable upper level divergence will drive a primary low northeastward along the windward side of the Appalachians today. Combination of absolute cyclonic vorticity advection and the actual low height anomaly will aid in an inverted surface trough and axis of low to midlevel convergence along the northwest flank through Southeast Michigan. The forcing will impact Southeast Michigan primarily between 12Z and 00Z Mon.
For today's system an interesting disconnect exists between deep and in some places (northern cwa) upright system relative isentropic ascent with a lack of any true sustained moisture transport.
Saturation is modeled to be quite high particularly between 900- 700mb but richest thetae advection occurs much farther southeast attendant to the surface low itself. Strong model signal exists in total precipitation of less than 0.25 inch with in-house time lagged ensemble calculating only a 20-30% chance of 0.25 inch and NBM 24 hr qpf 50th percentile at .25 to .30 inch north of M 59. No question that bulk of precipitation will fall in the form of rain with mild air below 1.5 kft agl. Basal portion of low height anomaly passes east of Lower Michigan before 00Z this evening which will allow northwest gradient flow to expand rapidly through the region.
Shallow cold advection will lower freezing heights and allow wet snowflakes to mix in with the precipitation especially north of M46.
No signal exists for any accumulations outside of trace amounts

Differential anticyclonic vorticity advection will allow a very weak area of surface high pressure to build across the state Monday and Monday night. Moisture field and forecast soundings support a brief period of very dry midlevel air pushing across the state Monday. So the possibility exists for some breaks in the clouds Monday afternoon across the northern cwa, but with continued upper level troughing and cyclonic flow its difficult to get too excited. A point of emphasis for Monday is just enough of a wind to keep wind chills values in the upper 20s to around 30 degrees.

A Clipper system continues to be advertised for Tuesday. Trends in the model data has been supportive of a more southerly track. Model soundings are sufficiently cold for all snow, with the only question being quality and degree of saturation. Models show saturation for now, but could dry out in future runs. System relative isentropic ascent is not at all favorable with a very shallow sloped frontal surface with system relative flow fairly parallel to the isentropes.
Best thetae advection is progged from nw to se along a line from South Bend to Defiance. The story is told in the probability guidance with latest NBM at only a 20 to 30 percent chance to exceed 0.1 inch of snow Tuesday with a 50th percentile of QPF at only 0.03 inches. Really not much potential for much.

MARINE...

Low pressure lifts into the region this morning leading to the expansion of rain showers across the region, with some snow mixing in over the northernmost portion of the area. Easterly winds strengthen through the morning-afternoon, focused over northern Lake Huron where peak gusts between 20-25kts are expected. System shifts east by Sunday night leading to modest (less than 20kt)
northwesterly flow setting in its wake. This shift will lead to building waves around the tip of the Thumb overnight into early Monday morning leading to borderline small craft conditions. With a slight upward trend in the wave model, have decided to issue a Small Craft Advisory for Sunday night over the outer Bay and Port Austin nearshore waters. Active weather pattern then continues through the week as a series of weak systems swing across the Great Lakes/Ohio Valley. That said, marine impacts still looking to be minor with main impact being repeated shots for rain-snow showers. Lack of significant cold air and weaker gradient with these systems not supportive of strong winds/subsequent headlines.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory from 7 PM this evening to 4 AM EST Monday for LHZ421-441.

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

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