Macomb, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

031
FXUS63 KDTX 221053
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
553 AM EST Sun Dec 22 2024

.KEY MESSAGES...

- After a cold start with early morning temperatures ranging from
  around zero I-69 north to around 10 Detroit south, daytime highs
  will remain chilly and range in the 20s today.

- Snow accumulation potential for a shortwave arriving on Monday
  continues to increase with several inches of snow expected from
  midday into the early evening.

- Highest snowfall amounts continue to focus from between M-59 and
  I-69 north, but with some accumulations of sleet or snow possible
  further to the south as well.

&&

.AVIATION...

A ridge of high pressure will pass across SE Lower MI this morning
with mostly clear skies and calm wind at press time. Stratus tied to
Lake Michigan is easing eastward across the state and will bring
potential for ceilings between 3 and 4 kft later this morning. As
the high departs east, wind will become organized out of the south
around 8 kt or below which will cause the stratus to lift north
through the afternoon. This gives way to increasing coverage of mid
cloud spreading in tonight ahead of low pressure over the Midwest.
This system will bring widespread snow to the area beginning midday
Monday.

DTW THRESHOLD PROBABILITIES...

* Medium for ceiling at or below 5000 feet today.

* Medium for ptype of snow and sleet after 16z Monday.

&&

.PREV DISCUSSION...
Issued at 332 AM EST Sun Dec 22 2024

DISCUSSION...

Despite the fact that arctic high pressure will continue to
gradually retreat to the east today, a cold start with minimum
temperatures in the single digits (in some cases negative single
digits along/north of the I-69 corridor) will lead to another chilly
day with maximum temperatures in the mid 20s on average (a bit
colder Thumb to a bit milder near the Michigan and Ohio state line.

Attention turns to a shortwave of Pacific Northwest origin which is
now rounding a flat upper ridge as it tracks from the northern
plains to upper midwest this morning. This wave will arrive in the
central Great Lakes on Monday and bring widespread precipitation.
Cold air in place on the edge of the arctic high will be sufficient
to allow for a fair amount of the precipitation to fall as snow,
especially from M-59 north. Further south, more of a wintry mix will
be possible given the degree of a warm layer that noses over the
edge of the modified arctic air mass. Here, snow/sleet with some
possible freezing rain/rain as temperatures hover in the lower 30s
into afternoon after starting in the 20s earlier in the day.

Model trends this evening continue to bring higher QPF amounts into
the area as a decent FGEN signal emerges with the associated low
pressure system that develops as the shortwave crosses the area.
Model spread remains relatively high in this regard though so the
overall confidence (while improving) remains suspect. That said,
HiRes solutions do point to higher snowfall amounts into the M-59
corridor with some accumulations possible further south.

Will be upping the snow forecast with a fairly broad-brushed 2-5
inches from M-59 north. In reality, the heavier swath of precip/snow
will most likely focus along the narrower FGEN feature with tapering
amounts on either side of this better forcing which works through
the area from mid afternoon into early evening after a more general
area of isentropic lift produces a more widespread lighter precip
shield from mid/late morning into the early afternoon.

Confidence in the position of this FGEN remains too low to refine
the forecast any further at this time. Some minor icing potential
will be possible over the far southern areas (mainly I-94 south),
but questions on the exact concentration of precipitation types
remain given the battle between a fairly deep cold layer off the
surface (2-3kft) and a notable mild wedge of air working into the
southern forecast area above this colder pocket of air. All in all,
it is fair to say that deteriorating conditions seem likely from
midday into the evening commute. The degree of this deterioration,
however, remains somewhat elusive. For what it is worth, the current
trend is for a more impactful event during the last half of the day.

In the wake of this shortwave, a pocket of cold air advection will
keep high temperatures in the middle 30s into the middle of the week
with a general warming trend then expected to ensue from late week
into next weekend as a steady flow of Pacific air overspreads the
CONUS. Temperatures are expected to rise into the 40s to around 50
during this portion of the forecast. So, a majority of precipitation
that falls during this time frame will be rain. Just how much rain
and the timing remains convoluted as models vary in how a series of
southern stream shortwaves that emerge off the Pacific Ocean will
evolve as their connection (or lack thereof) to any northern stream
energy remains questionable.

MARINE...

High pressure slides across the region today maintaining lighter
winds and drier conditions. Southerly flow then strengthens tonight-
Monday as compact low pressure ejects out of the Plains into the
Great Lakes. Peak gusts during the day Monday expected to reach the
25-30kt range over Lake Huron; gusts over the southern Great Lakes
stay 20-25kts. Despite the offshore flow, winds could be strong
enough to support small craft criteria (3-5+ft) waves in the Thumb
nearshore waters. This system tracks over the area latter half of
Monday into early Tuesday generating widespread snow with winds
slowly veering from NW to NE on the backside of the system Tuesday.
High pressure is quick to build back into the region in the low`s
wake resulting in winds weakening once northerly flow develops.

&&

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

$$

AVIATION.....TF
DISCUSSION...DG
MARINE.......KDK


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at www.weather.gov/detroit.