Macomb, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

779
FXUS63 KDTX 202342
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
742 PM EDT Fri Jun 20 2025

.KEY MESSAGES...

- Scattered to numerous showers and thunderstorms develop late
tonight and taper off Saturday morning. Storms may be strong to
severe.

- Becoming hot and windy Saturday afternoon. Heat advisory issued
for Saturday afternoon and Saturday night.

- Extreme Heat Watch remains in effect for Sunday through Tuesday
evening.

- Record/near record heat Sunday and Monday. High temperatures well
into the 90s and heat index of 100-105 degrees, with minimal
relief at night.

- Very warm mid week, with periods of showers and thunderstorms
Tuesday-Friday.

&&

.AVIATION...

Eastern edge to lead isentropic ascent has resulted in a altostratus
deck at approximately 10.0 kft agl across much of Southeast Michigan
this evening. Significant warm air and thetae advection aloft is
ongoing immediately upstream which will initially erode cloud, before
contributing to elevated instability tonight. Uncertainty does exist
with the development, coverage, and track of thunderstorm activity
tonight. Some model data (ECMWF and GEM) carries the MCS well to the
north of Lower Michigan and Lake Huron, whereas the (NAM and ARW)
develop some unorganized elevated thunderstorm activity over
portions of western and central Lower Michigan before tracking
eastward. Given the magnitude of the warm advection, will respect
the synoptic forcing and carry prevailing thunderstorm groups at
KMBS and KFNT between 10z-14Z and Prob30 groups at the Detroit
terminals for the same period. Midlevel warm air is eventually
expected to result in convective inhibition and capping by Saturday
afternoon.

For DTW/D21 Convection...The potential exists for thunderstorm
activity between 10-14Z. Low confidence exists on how far southward
the thunderstorms will develop.

 THRESHOLD PROBABILITIES...

* Low for thunderstorms Saturday morning.

&&

.PREV DISCUSSION...
Issued at 252 PM EDT Fri Jun 20 2025

DISCUSSION...

Big pattern shift this weekend into early next week, as a strong
upper level ridge builds over the Central Appalachians, leading to a
dangerous heat wave, as temperatures reach record or near record
highs Sunday and Monday.

Before we get there, will have to content with a period of strong to
severe thunderstorms tracking through the Central Great Lakes late
tonight, as yet another shortwave tracks southeast downwind of the
ridge axis. Increasing moisture and instability with a several surges
occuring. Pretty good coverage of showers (more extensive than hires
solutions suggested) this morning triggered by lead 850-700 MB
theta-e ribbon which came out of Wisconsin. Very short lived/subtle
drying/subsidence 20-23z over much of the CWA this afternoon
complicates the forecast during peak heating, as there should be
decent SB(1500+ J/kg)/ML(500+ J/kg) capes with dew pts in the mid 60s
and temps rising into upper 70s-lower 80s. Not much of a trigger
and/or sustaining of updrafts with unidirectional westerly winds.
However, perhaps just enough wind in the column with marginal
downdraft capes for an isolated cell to approach severe limits if
storms go up. Currently, overcast skies are not showing a whole lot
of indications of clearing, making stronger activity highly doubtful.

Much bigger concern with the reservoir of moisture/instability over
the Midwest which will be released eastward tonight and warm front
likely activates with mid level jet tracking through the Central
Great Lakes tonight. Lead edge of the moisture gradient arrives
around midnight, which could start the activity, but warm advection
arm/850-700 MB Theta-ridge arrives around 9z, and the more favored
time (9-13Z) with the arrival of the low level jet (40+ knots).
Showalter indices (-8 C) and K index (44 c) are very impressive, with
MUcapes of 2000-3000 J/kg feeding in, supporting large hail and
torrential rain threat. 12z HRRR/ARW depiction seem like a reasonable
scenario, and enough confidence to carry likely pops late tonight.
Not sure if we can fully count on the modest surface based inversion
to prevent damaging winds from reaching the surface in the strongest
cells, and machine learning hinting at this possibility.

Aggressive warming/height rises during the afternoon cap and prevent
additional activity, with 850 MB temps surging into the lower 20s,
supporting highs in the lower 90s by day`s end. Heat indices peaking
out around 100 degrees based on lower 70 dew pts. It will become
wind as well, as good boundary layer mixing with the leftover
stronger wind fields support wind gusts of 35-45 mph, per local
probabilistic guidance, strongest in the Saginaw Valley with the
favorable southwest flow.

With the previously mentioned heat indices for Saturday, have issued
a heat advisory for Saturday afternoon-Saturday Night and will
maintain the extreme heat watch for Sunday through Tuesday. Sunday
and Monday look to be the peak of the heat and humidity, as Euro mos
supports mid to upper 90s, which is record territory (see climate
section). General subsidence leading to dry and warm mid levels (12
C temps at 700 MB) should be enough to cap activity, as Euro also
indicating 1000-500 MB mean RH down around 30 percent. With the
lower 70/around 70 dew pts continuing, heat indices should peak
near 105 degrees both Sunday and Monday.

Still some uncertainty on how fast the upper level ridge in place
breaks down or drifts south during the mid week period, with the
moisture axis/frontal boundary over the Great Lakes region providing
the focus for multiple rounds of showers and thunderstorms to end
the work week. Models usually break down the stronger ridges a bit
too fast, so temperatures exceeding 90 degrees on Tuesday for the
4th consecutive day over at least the southern half of the CWA seems
likely.

MARINE...

An active stretch of weather is expected through the weekend. This
begins with a remnant MCV that has just crossed Lake Michigan, and
will trigger additional pop up showers and thunderstorms between now
and 8pm. A more organized thunderstorm complex will track in from
the northwest early Saturday morning, impacting the Great Lakes
between roughly 4am-10am. The primary hazards are torrential
downpours and frequent lightning, but gusts of 34+ knots and large
hail will be possible on an isolated basis. Drier conditions prevail
Saturday afternoon, albeit increasingly hot and humid. Winds by this
point organize out of the southwest, with land-based gusts
approaching 30-35 knots. While the seasonably warm conditions will
create stable conditions over water, locations near the shoreline are
more likely to see gusts exceed Small Craft Advisory thresholds (25
knots) late afternoon-evening. Advisories have therefore been issued
for all of the Lake Huron shoreline, while remaining Lake St. Clair
and western Lake Erie zones are only expected to briefly see gusts
approach these thresholds.

HYDROLOGY...

A warm front lifting through Lower Michigan tonight will bring the
potential to support showers and thunderstorms. Instability and
moisture will be on the increase, with PW values topping out around
2 inches. Thus, any strong thunderstorms that develop will produce
torrential downpours. Uncertainty exists with the areal coverage of
the activity, with main window looking to be 4 - 10 AM Saturday
morning. There is the potential for local rainfall totals to exceed
2 inches in a short period of time, which would lead to urban and
low lying flooding. Recent rainfall over the past couple of days has
made many areas more susceptible to flooding.

CLIMATE...

The record highs for Sunday, June 22nd.

Detroit: 98 Degrees (Set in 1988)
Flint:   96 Degrees (Set in 1923)
Saginaw: 94 Degrees (Set in 1966)

The record high minimums for June 22nd.
Detroit: 73 Degrees (Set in 1988)
Flint:   71 Degrees (Set in 1988)
Saginaw: 69 Degrees (Set in 2024)

The record highs for Monday, June 23rd.

Detroit: 95 Degrees (Set in 1923)
Flint:   98 Degrees (Set in 1923)
Saginaw: 96 Degrees (Set in 1923)

The record high minimums for June 23rd.
Detroit: 74 Degrees (Set in 1923)
Flint:   71 Degrees (Set in 2013)
Saginaw: 72 Degrees (Set in 1975)

The record highs for Tuesday, June 24th.

Detroit: 97 Degrees (Set in 1952)
Flint:   95 Degrees (Set in 1934)
Saginaw: 96 Degrees (Set in 1938)

The record high minimums for June 24th.
Detroit: 74 Degrees (Set in 1923)
Flint:   73 Degrees (Set in 1997)
Saginaw: 73 Degrees (Set in 1997)

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...Heat Advisory from 2 PM Saturday to 8 AM EDT Sunday for MIZ047>049-
     053>055-060>063-068>070-075-076-082-083.

Lake Huron...Small Craft Advisory from noon Saturday to 4 AM EDT Sunday for
     LHZ421-422.

     Small Craft Advisory from noon to 10 PM EDT Saturday for LHZ441>443.

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

$$

AVIATION.....CB
DISCUSSION...SF
MARINE.......MV
HYDROLOGY....SF
CLIMATE......SF


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