South Lyon, Michigan Weather Forecast Discussion

300
FXUS63 KDTX 142305
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
705 PM EDT Sun Sep 14 2025
.KEY MESSAGES...
- Patchy fog expected again Monday morning with areas of fog possible
  along the lakeshores.
- Much above normal highs with continuing dry weather next week.
&&
.AVIATION...
Reinforcement of high pressure from northern Ontario/Quebec provided
NE wind across Lake Huron and easterly wind off Lake Erie today. The
wind pattern is primarily responsible for afternoon observations of
Td in the mid to upper 50s across SE Mi that held up within the well
mixed boundary layer. Dissipation of high based cumulus this evening
leads to another favorable setup for radiational cooling and fog
and/or stratus late tonight and Monday morning. Surface wind trends
will be monitored for potential to hold near 5 knots after sunset as
that will play into the fog vs stratus distribution. The forecast
leans toward stratus upon examination of model soundings and hi-res
wind/RH guidance, especially toward DTW where wind direction has a
SE component off western Lake Erie. Full sun to start the morning
ensures a standard mid September pace of fog/stratus dissipation
leading into another afternoon of just fair weather cumulus Monday
afternoon.
For DTW/D21 Convection... No thunderstorms tonight and Monday.
THRESHOLD PROBABILITIES...
* Low for ceiling at or below 200 ft, or visibility below 1/2 SM
  early Monday morning.
&&
.PREV DISCUSSION...
Issued at 317 PM EDT Sun Sep 14 2025
DISCUSSION...
Surface high pressure and building upper level heights will govern
conditions across SE Michigan over the next several days. The 12z
KDTX RAOB depicts a very dry airmass aloft, with 700-600mb layer
dewpoint depressions near 40 C. Lake moisture has proven necessary
for diurnal cu development, with the cu field hugging the edge of the
marine layer. Dewpoints currently in the mid-50s are nearly
identical to crossover temperatures from yesterday with similarly
favorable radiational cooling potential to support patchy to areas of
fog Monday morning. This pattern holds in place through at least
mid-week as the upper ridge transitions to a rex blocking pattern.
Temperatures may climb a degree or two each day due to airmass
modification, although the warmest day is anticipated to be Thursday
when winds shift to the southwest and kick off modest warm advection.
Upstream, mid-level WV depicts two separate trough axes with
embedded shortwaves: the first extending from the Plains into
Alberta, and the second onshore the Pacific coast. Deterministic
models have started to converge on the solution that keeps these
troughs out of phase through the first half of the week, but they
will dislodge/weaken the upper ridge as they pivot to the north.
Eventually, the trailing trough is expected to evolve into an upper
low and settle into the Plains. This system would begin to influence
the Great Lakes Friday-this weekend, although ensemble members still
show quite a bit of variability due to uncertain interference
between the multiple waves. In general, the expectation is a shift
toward a wetter pattern for the weekend.
MARINE...
A ridge of high pressure will bring an extended period of dry
weather and lighter winds to the Great Lakes through the week. Some
localized higher wind speeds nearing 15 to 20 knots will be possible
into the Saginaw Bay this afternoon and evening and again tomorrow
afternoon and evening given the favorable northeast fetch.
Otherwise, the next chance for more active weather will enter next
weekend as a low pressure system nears the region.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....BT
DISCUSSION...MV
MARINE.......AM
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NWS DTX Office Area Forecast Discussion