Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 021737

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1237 PM EST Sat Dec 2 2023


Influence from a ridge of high pressure over the northern Great
Lakes has brought steady mid-level subsidence today, strengthening
the inversion around 4000 ft and trapping abundant moisture beneath.
The low clouds have lifted slightly to borderline IFR/MVFR for many
sites, which should hold through the afternoon. Expect the onset of
nocturnal cooling to trend ceilings back down to IFR, especially as
light northeast wind off Lake Huron continues to supply a marine
moisture contribution. A period of drizzle is likely overnight,
preceding the arrival of more widespread light rain Sunday morning
as the next low pressure system moves in from the south. This will
keep the lower ceilings around with guidance showing high
probabilities for at least IFR to hold through the end of the
period. The cooler air will be held to the northwest, limiting the
chance for any snow on Sunday - though MBS may see a few melting
flakes mix in.

For DTW...Lower MVFR conditions to start the period, but will likely
see IFR settle back in by this evening. High confidence in rain on
Sunday, mainly between 13z and 22z.


* High in ceilings below 5000 feet this afternoon through Sunday.

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


Issued at 348 AM EST Sat Dec 2 2023


Light rain showers continue across southern MI early this morning
due to a combination of weakening elevated Fgen and deformation tied
a surface low that is passing along the MI/OH border. The deeper
moisture pushes off to the east this morning but a remnant moist
boundary layer up to around 6kft will linger through the day within
the surface trough and under a weak subsidence inversion helping to
trap the moisture. This should lead to a grungy day with low clouds
and drizzle. The trough will prevent any thermal advection in either
direction thus we should be locked in with temps similar to
yesterday with highs around 40. Little more amplified shortwave
ridge passes over tonight but should only compress the remaining
BL moisture, keeping low clouds locked in and possible drizzle.

Pattern remains active with several waves reinforcing the upper
level trough which is stretching from the Plains toward the Great
Lakes by Sunday. The next wave is a strong mid level wave which will
be positioned over the Mid MS Valley Sunday morning. The 160+ knot
jet stretching from LA to NY will take this wave across the Ohio
Valley late in the day. Positioning just to our south will put us
under upper level diffluence through the day with a surface low
tracking across lower MI, just to the north of the track Friday`s
low took. This will bring our next round of showers which will be
mainly rain once again. Proximity to the cooler air to the northwest
will keep a rain/snow mention again for Mid and Northern MI. One
notable difference from the Friday low will be less available
moisture as the axis of deeper moisture will be well off to the SE.
So PWATs will be up to around 0.5 inch, and QPF amounts should be
around 0.25 inch. There will be no snowfall accumulations mentioned
at this time.

Trough slides east for the beginning of the week putting us in the
coldest of the air within it, albeit only around -5C at 850mb. So
highs should fall a bit to start the week into the upper 30s. Monday
will offer a brief break in precip with shortwave ridge axis sliding
over, but the next shortwave diving down the backside of the trough
will then slide through on Tuesday. This will be more of a clipper
system with poor moisture quality. In terms of temperatures, the PV
axis looks to pivot through to the northeast pulling warm air up
into the region. A daytime clipper with surface temps near 40 should
help produce at least a rain/snow mix for the area. Will watch
thermal trends and soundings to see if anything offers a better snow
signal or not.


Low pressure centered over the southern Great Lakes maintains
showers and northeasterly flow through the morning. Wind direction
maintains elevated wave action around the tip of the Thumb/Bay until
low pressure vacates the region this afternoon allowing winds to
weaken slightly and turn more easterly. Another developing low
quickly follows for Sunday taking a similar track to the
Friday/Saturday system. Impact is another round of rain and snow
showers as well as a modest uptick in easterly winds, though peak
gusts over northern Lake Huron expected to hold sub 25kts.
Northwesterly flow redevelops on the backside of the low late Sunday
into Monday potentially resulting in rougher small craft conditions
around the tip of the Thumb.


Lake Huron...Small Craft Advisory until 4 PM EST this afternoon for LHZ421.

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



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