Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241038
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
538 AM EST Wed Jan 24 2018

.AVIATION...

Maintenance of a cold and weakly cyclonic flow will sustain an
extensive stratus deck through the daylight period. Recent
observations remain in support of predominate MVFR conditions during
the latter half of the morning. The combination of continued cold
air advection and daytime heating will work to lift ceiling heights
through the day. This may provide a window for VFR conditions to
eventually emerge by mid-late afternoon. Some uncertainy yet with
timing the decrease in cloud coverage tonight. Tentatively will maintain
a general clearing trend overnight, but expect addition refinement
as near term trends and short range model guidance provide a more
definitve signal. Diminishing northwest winds today, turning
light/variable tonight.

/DTW THRESHOLD PROBABILITIES...

* High for ceilings less than 5000 ft today. Low tonight.

&&

.PREV DISCUSSION...
Issued at 339 AM EST Wed Jan 24 2018

DISCUSSION...

Quiet stretch of weather taking us through the rest of the week as
expansive surface ridge slides through the region. The ridge will
start building across lower MI later this evening leaving a short
period of lingering cyclonic flow through the early part of the day.
A stout inversion is trapping lingering boundary layer moisture
which looks to hold through the day. Cold advection will help
steepen low level lapse rates today which combined with a weak cold
front, and the saturation layer getting into the -12C layer to
produce some flurries. Better chances of snow showers will occur
just south of the state as a vort max drops through the base of the
trough through the Ohio Valley.

Surface ridge then builds into the area later this evening with
overall height field on the rise tonight as a mid/upper level ridge
begins to build into the Midwest and western Great Lakes Thursday.
The thermal trough will hold today and moderate slightly Thursday
before drifting east so expect highs today only in the upper 20s to
low 30s, and a few degrees higher Thursday.

Friday starts the next brief warm up as the ridge axis cross lower
MI opening the door for southwesterly return flow, warm air
advection and more sun. This will all combine to help high temps
rise to near 50 degrees. The longwave pattern becomes progressive
bringing the next low across Ontario on Saturday. Being well north
of the area, we will stay embedded in the warm sector ahead of the
trailing cold front which is set to pass through lower MI Saturday
afternoon. The timing of the fropa should allow temps to once again
rise to near 50. Models starting to come together a bit more with
this, leaning more toward a southern stream wave getting picked up
by the trough and spinning up a low along the cold front. How fast
it all comes together will dictate how much rain falls across
southern MI. Model consensus suggests the front will initiate
overhead but developing downstream keeping most of the QPF to our
east. Timing will be everything with the front and how quickly the
southern wave gets lifted north.

Only slightly cooler air works into the region with WNW flow in the
wake of the initial cold front Saturday with 850mb temps falling
from 6C to 0C. A secondary cold front will then drop through Sunday
afternoon which will drop the 850mb temps to -12C. Along with the
front, some shortwave activity within the trough will bring a chance
of snow showers Sunday into Monday.

MARINE...

Diminishing north to northeast winds today, as the gradient eases
in response to high pressure drifting across the northern great
lakes. Relatively light winds will remain in place tonight and
Thursday under weak surface ridging. Southerly winds will strengthen
on Friday. This will be accompanied by an increase in stability, as
warmer air moves back into the region. This will confine gusts to 30
knots or less across lake Huron. A period of moderate southwest
winds will exist on Saturday as a cold front lifts into the region.
This frontal boundary will bring the next chance for precipitation
during the first half of the weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&

$$

AVIATION.....MR
DISCUSSION...DRK
MARINE.......MR


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