Macomb, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

850
FXUS63 KDTX 041928
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
328 PM EDT Mon May 4 2026

.KEY MESSAGES...

- Red Flag Warning in effect for locations along and north of the I
69 corridor until 7pm tonight.

- A chance of thunderstorms this evening into tonight. Much of the
forecast area is in a Marginal or Slight risk designation for Severe
weather with large hail, strong wind gusts, and a brief weak tornado
potential threats.

- Low confidence exists in the timing and duration of rain Tuesday
and Wednesday.

- Much cooler temperatures return Tuesday and last through the end
of the week. A Frost Advisory or Freeze Warning may be needed.

&&

.DISCUSSION...

Well mixed southwesterly flow has developed over all of Southeast
Michigan this afternoon with 2pm wind gusts at a few of the ASOS
sites reaching and exceeding 45 mph. Surface moisture has mixed out
over much of the northern cwa with many observing platforms
reporting relative humidity between 19-25 percent. With dry
southwest flow persisting this afternoon and with collaboration
considerations, decided to go with a Red Flag Warning in effect
until 7pm this evening.

Atypical, in-phase squeezing event of northern stream Canadian
trough and Southwestern United States ridge will result in a
strengthening baroclinic zone over portions of Lower Michigan and
northern Ohio River Valley by Tuesday. Two boundaries reflect this
competing geopotential height pattern: the first is the deep cold
front progressing through the Lake Superior basin, the second is a
thetae/CAPE gradient that will emerge and lift into far southern
portions of Southeast Michigan between 21-03z this evening.

Very subtle forcing mechanism at work across the forecast area this
afternoon with a lack of upper level jet dynamics and synoptic lift
locally. Differential loss of the anticyclonic flow trajectories over
Southeast Michigan is expected to allow for a region of height
falls, inducing northward moisture transport of 900mb thetae
content. Remnant midlevel dry adiabatic lapse rates with help from
the Evening Transition will result in the development of mixed layer
CAPE exceeding 1000 J/kg with the CAPE gradient lifting northward
through Metro Detroit. CAM output is quite bullish on convective
initiation/development along the boundary 22-01z. 0-6mb bulk shear
of 30 to 35 knots will be adequate for storm organization, although
hiresolution data shows little signal for storm right movement. CAPE
gradient boundary does become parallel to the 850-300mb mean flow
suggesting a potential for training of activity. Therefore, large
hail and localized heavy rainfall are the main threats this evening.
Forecast soundings do suggest higher static stability developing
with the loss of daytime heating from the surface to 4.0 kft agl
suggesting strong wind gusts may be more difficult to observe outside
of any organized cold pool or forward propagation. The threat of a
tornado appears to be very low although a boundary is overhead with
0-1km SRH that reaches 150 m2/s2.

The Canadian trough will encroach on the area tonight driving the
deep cold front through the area. Differences exist on how generous
the coverage of showers and embedded thunderstorms will be overnight
highlighted by the latest forecast with PoPs at generally less than
60%. Models show a dead zone of both the 700 and 850mb frontogenesis
over Southeast Michigan but with deep southwest flow the potential
exists for upstream activity to track through the area. MUCAPE of
250-500 J/kg in place ahead of the cold may support some small hail
between 02-05z. The latest SWODY1 has areas south and west of a line
from Chesaning to Grosse Pointe designated as a Marginal Risk for
Severe weather and a Slight risk across southern Lenawee and Monroe
counties.

Uncertainty exists with regards to precipitation timing and coverage
Tuesday midday through late Wednesday morning. Low confidence arises
from stark differences in the occurrence and subsequent timing of a
wave of low pressure set to track northeastward along the baroclinic
zone. Latest data of system relative flow on isentropic surfaces
supports the surface cold front clearing the area 15-18z with
lingering lower column RH overhead. CAM simulated Z supports
decaying nocturnal showers pushing through Metro Detroit southward
between 15-21z Tuesday which is supported by likely PoPs. The
solution space then diverges greatly Wednesday with the NAM the most
bullish on an organized low pressure circulation tracking along the
Ohio River. This would bring a fairly lengthy period of midlevel
isentropic ascent to the southern cwa Wednesday. The current
forecast is very lean on PoPs for the Wednesday period.

Low geopotential heights are forecasted to persist over the central
Great Lakes through the end of the week and upcoming weekend.
Lowered midlevel temperatures will likely support typical afternoon
instability shower chances. The biggest item will likely be the need
for Frost and/or Freeze headlines particularly Thursday morning.
Some moderation in temperatures to near normal is possible by this
weekend but the forecast will likely be determined by the amount of
clouds over the region.

&&

.MARINE...

Breezy southwest winds prevail across the area this afternoon,
though the warmer air mass overriding the cooler Great Lakes waters
has allowed for a more stable environment with wind gusts mostly
remaining below 25 knots. Fetch across the Saginaw Bay remains
favorable for locally stronger winds, so have maintained the ongoing
Small Craft Advisory through the evening hours. Isolated to
scattered showers and embedded thunderstorms will be possible later
this afternoon and evening, most favorable across Lake Erie and Lake
St. Clair. Any stronger storm development will be capable of
producing small hail and wind gusts of 34 knots or stronger.

A cold front dropping south across the western half of Lake Superior
this afternoon will gradually work south across the region late
tonight and into Tuesday morning. Winds from the north briefly
dominant behind the cold front, but then lessen in speed and become
more variable during the day Tuesday. Tuesday night through
Thursday, winds will back from the northeast to north and eventually
from the west, as another area of low pressure organizes south of
the region and moves over the Northeast.

&&

.PREV DISCUSSION...
Issued at 1225 PM EDT Mon May 4 2026

AVIATION...

Well-mixed boundary layer allowing for southwest winds to gust AOA
25 knots this afternoon. Despite the moderate southwest winds, low-
level moisture is slow to advect into the state, and a cap should
hold through 20Z, limiting low cloud development. A chance of
showers and storms develop over the southern TAFs during the evening
hours. A cold front slowly tracking through tonight brings a chance
of showers and low VFR/borderline MVFR ceilings, with embedded
thunder not out of the question.

D21/DTW Convection...Inherited timing of 23Z-03Z for thunderstorms
looks good, but confidence in a direct impact is still not high
enough to upgrade from PROB30. Strong wind gusts and hail are
possible should a strong or severe storm intersect the airfield.
Heavy downpours could result in brief IFR reductions. Additional
showers are expected overnight into Tuesday morning as a cold front
tracks through, some of which could include embedded thunder. Winds
will shift to the northwest mid-to-late Tuesday morning.

DTW THRESHOLD PROBABILITIES...

* Low for thunderstorms this evening and tonight.

* Low for ceiling at or below 5000 feet this evening and tonight;
  medium tomorrow.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Red Flag Warning until 7 PM EDT this evening for MIZ047>049-053>055-
     060>062.

Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422.

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

$$

DISCUSSION...CB
MARINE.......JA
AVIATION.....SF


You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.