Tornado and Flood in Michigan, April 4 to 5, 2026

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
627 AM EDT Sat Apr 4 2026

.KEY MESSAGES...

- Widespread showers and some embedded thunderstorms are expected
today.

- Chance for isolated strong to severe thunderstorm development this
afternoon, favored along of south of I-94.

- Below normal temperatures Sunday through early next week.

&&

.AVIATION...

Moist low level easterly flow north of a warm front will maintain
widespread IFR to MVFR conditions within areas of elevated
convection this morning. Observational and radar trends suggest some
pockets of embedded thunder will remain possible through late
morning mainly across MBS and possibly Flint. Some increase in cloud
base occurs as the warm front lifts northward 15z-18z, with a wind
shift to south-southwest with some gustiness. A secondary period of
convection expected along the eastward propagating cold front from
mid afternoon into early evening. Forecast will continue to
highlight the best window thunderstorms generally between 19z and
22z, with a focus across the Detroit airspace where modest pre-
frontal instability will develop. Winds turn westerly within the
post-frontal environment with continued gustiness. Cloud trends
overnight carry less certainty as this stage, with a mixed signal
yet on degree of any clearing. Conservative approach in maintaining
a lower cloud deck at this stage.

For DTW...Potential for thunderstorms to develop between 19z and 22z
today.

.DTW THRESHOLD PROBABILITIES...

*  High for ceiling at or below 5000 ft through this afternoon. Low
   tonight.

*  Moderate for thunderstorms Saturday between 19z and 22z.

&&

.PREV DISCUSSION...
Issued at 348 AM EDT Sat Apr 4 2026

DISCUSSION...

Occluded low pressure system now over northern Illinois and southern
Wisconsin will continue to progress across northern lower Michigan
this afternoon before departing into eastern Ontario and Quebec by
late tonight. Progression of the low has resulted in numerous rain
showers with some embedded thunderstorms across SE MI with shallow
isentropic ascent along an advancing warm front. Isolated
thunderstorms with heavy downpours remain possible through the
morning hours, capitalizing on modest MUCAPE, but activity remains
elevated noting the sharp inversion in the low levels with the 00Z
RAOB. The 40+ knots llj on the southern flank of the low will result
in extremely efficient moisture transport with pw values around 1.40
inches, which if verified would fall outside record values for early
April per local sounding climatology. Moisture convergence with
additional forcing ahead and along of a cold front will bring
widespread rain and embedded thunderstorms through the afternoon and
evening. A lull in activity will be likely across the Metro region
and down into the MI/OH border later this morning, with prolonged
rain chances setting up through the Tri-Cities, where the low and
occluded front lies. This will coincide with the higher rainfall
totals, as described in the hydrology section.

Latest 12Z data highlights a small window for some isolated strong
to severe storms from roughly 18Z (2PM) to 22Z (6PM), favored along
or south of I-94, where surface based cape briefly wedges in ahead of
the cold front. HREF mean CAPE values range from around 800 J/kg
down to the MI/OH border and upwards to 300 J/kg across the Metro
region. Hodographs are relative straight from 0-3km owing to the
unidirectional winds. Any type of development just ahead or along the
cold front could have some better structure with some bowing that
would be capable of producing damaging wind gusts with localized gust
potential to around 60 mph. ML-output highlights a slightly elevated
chance for tornado probabilities within the same area -- 0-3 km
shear vector orientation is poor relative to the projected storm
motion and 0-1km hodographs are not conducive to tornadogenesis.
However, cannot rule out some highly localized streamwise vorticity
driven by backed surface winds along the marine layer interface. Any
overachievement of instability could expand the footprint for strong
to severe potential into the north Metro region through Port Huron as
highlighted in the latest SWODY1, but confidence in this expanded
footprint is low.

The strong cold front moves through by the late evening, ending all
rain chances while advecting in much cooler air. Lows drop into the
30s Sunday morning, which paves the way for below normal
temperatures to last through the early week period. The next likely
chance for some wintry precipitation then enters on Monday as a
series of shortwaves arrive across the Great Lakes. Morning
temperatures in the 30s bring the chance for melting snow to a
rain/snow mix. Temperatures warm up into the 40s by the afternoon
bringing increasing chances for rain, but steep lapse rates and lower
freezing levels could bring some graupel with any convective based
showers. A strong high pressure builds in Tuesday which effectively
ends any precipitation chances. Clearing skies does bring what will
likely be the coldest temperatures of the week, with lows in the 20s
and highs holding in the 30s to low 40s Tuesday.

MARINE...

Easterly wind increases this morning ahead of a deepening low
pressure system tracking in from the mid-Mississippi Valley. 20 to
25 kt winds with gusts to 30 kt are forecast today, with the highest
wind magnitude across northern Lake Huron where fetch is maximized.
Brief gusts to 35 kt gales will be possible at times in this area
mainly between 8am and 2pm, but confidence is too low for a Gale
Warning. Showers and thunderstorms overspread the area today, some
of which may be strong to severe in the south. As the center of the
low reaches the Straits this evening, wind direction veers around to
southwest and remains gusty to around 20 to 25 kt. Strong cold
advection follows this system on Sunday with gusts of 25 to 30 kt
likely through the day. A Gale Watch was considered for northern
Lake Huron on Sunday for 35 kt gales, but confidence remains below
criteria at this time. Small Craft Advisories have been issued for
the Lake Huron nearshore waters and additional advisories are
possible for Lake St. Clair and western Lake Erie for Sunday. The
gradient relaxes Monday causing wind magnitude to weaken, then a
series of clipper systems bring cooler air and chances for snow
showers Monday and Tuesday.

HYDROLOGY...

Several rounds of scattered to widespread rain with embedded
isolated thunderstorms continues through the morning hours. A lull
in precipitation will be likely across southern Michigan, before a
cold front then brings a line of widespread showers and embedded
thunderstorms this afternoon and evening. The Tri-Cities and northern
Thumb will experience longer residence time for precipitation today
given the track of the low pressure system. This brings increasing
probabilities for local totals to achieve or exceed 1", with the
current forecast highlighting possibly totals between 1 to 1.5"
across the Tri-Cities and northern Thumb.

For locations south, basin averages range between a half-inch to
three-quarter inches. However, any thunderstorm activity will be
capable of producing localized total nearing or exceeding 1".
Several river flood warnings are in effect across the Saginaw river.
Localized flooding in low-lying or flood prone areas remain possible
with any thunderstorm activity.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT Sunday for LHZ421-441.

     Small Craft Advisory from 4 PM this afternoon to 10 PM EDT Sunday
     for LHZ422.

     Small Craft Advisory from 10 AM this morning to 10 PM EDT Sunday
     for LHZ442-443.

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

AVIATION.....MR
DISCUSSION...AM
MARINE.......TF
HYDROLOGY....AM

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

Hazardous Weather Outlook
National Weather Service Detroit/Pontiac MI
359 AM EDT Sat Apr 4 2026

MIZ047>049-053>055-060>063-068>070-075-076-082-083-050800-
Midland-Bay-Huron-Saginaw-Tuscola-Sanilac-Shiawassee-Genesee-Lapeer-
St. Clair-Livingston-Oakland-Macomb-Washtenaw-Wayne-Lenawee-Monroe-
359 AM EDT Sat Apr 4 2026

This hazardous weather outlook is for southeast Michigan.

.DAY ONE...Today and Tonight

Scattered to numerous showers with embedded thunderstorms will be
likely today. There is a marginal to slight risk for severe weather
this afternoon, most favorable along and south of I-94 between 2 PM
to 6 PM. The main severe hazard will be localized damaging wind
gusts to 60 mph. A tornado cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today and tonight.

LCZ460-LEZ444-LHZ361>363-421-422-441>443-462>464-050800-
Lake St Clair-
Michigan Waters of Lake Erie from Detroit River to North Cape MI-
Lake Huron from 5NM east of Mackinac Bridge to Presque Isle Lt
beyond 5 NM off shore-
Lake Huron from Presque Isle Light to Sturgeon Point MI beyond 5NM
off shore-
Lake Huron from Sturgeon Point to Alabaster MI beyond 5NM off shore-
Outer Saginaw Bay SW of Alabaster to Port Austin MI to Inner Saginaw
Bay-Inner Saginaw Bay SW of Point Au Gres to Bay Port MI-
Port Austin to Harbor Beach MI-Harbor Beach to Port Sanilac MI-
Port Sanilac to Port Huron MI-
Lake Huron from Port Austin to Harbor Beach beyond 5NM Off Shore-
Lake Huron from Harbor Beach to Port Sanilac beyond 5NM Off Shore-
Lake Huron from Port Sanilac to Port Huron beyond 5NM Off Shore-
359 AM EDT Sat Apr 4 2026

This hazardous weather outlook is for portions of Lake Erie, Lake
Huron and Lake St Clair.

.DAY ONE...Today and Tonight

Scattered to numerous showers with embedded thunderstorms will be
likely today. There is a marginal to slight risk for severe weather
this afternoon, most favorable across western Lake Erie to Lake St.
Clair between 2 PM to 6 PM. The main severe hazard will be localized
wind gusts at or above 34 knots.

Small Craft Advisories are in effect across the Saginaw Bay to Port
Huron. Please see the marine forecast for additional details.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Small Craft Advisories are in effect across the Saginaw Bay to Port
Huron on Sunday. Please see the marine forecast for additional
details.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today and tonight.

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

AM