Expert Forecast Opinion

186
FXUS63 KDTX 091001
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
601 AM EDT Mon Mar 9 2026

.KEY MESSAGES...

- Ample sun and very warm today.

- Isolated showers possible Tuesday, becoming wetter with rising
thunderstorm potential Tuesday night into Wednesday. The potential
exists for severe storms early Wednesday morning.

- Rain showers change over to melting snow showers by Wednesday
night with minimal accumulations.

- A clipper system may produce wintry precipitation Friday.

&&

.AVIATION...

Low pressure passes north of Lake Superior today with Lower MI
situated within its warm sector. Daytime heating taps into gusty
wind aloft, producing southwest surface wind of 15-20 kt with gusts
to 25-30 kt through the morning. As the gradient relaxes this
afternoon and evening, wind magnitude will gradually subside. VFR
conditions through the day before low-level moisture arrives from
the Mid-Mississippi Valley overnight, bringing potential for MVFR
ceilings early Tuesday morning. Some drizzle/mist may also accompany
this push of moisture mainly after 09z. Meanwhile, a backdoor cold
front marked by a northeast wind shift begins advancing southward
into the Saginaw Valley and Thumb late tonight with uncertainty on
its southward progress by 12z Tuesday.

For DTW...Low confidence in patchy drizzle developing early Tuesday
morning, with high confidence in temps well above freezing during
this period.

DTW THRESHOLD PROBABILITIES...

* Medium for ceiling at or below 5000 ft after 06z tonight.

&&

.PREV DISCUSSION...
Issued at 322 AM EDT Mon Mar 9 2026

DISCUSSION...

Straight zonal flow over the northern Plains into Southern Canada
today will result in broad southwesterly flow across much of
southern Lower Michigan and aid in the development of a stationary
front south of the Straits down to Saginaw Bay. Consistent model
signal continues with clear skies today and temperatures warming
into the middle to upper 60s, approximately 25 degrees above normal.
Decent model signal in low level, 925-700mb, thetae advection into
Southern Lower Michigan. The moisture advection is expected to both
increase clouds tonight and reinforce the stationary front a little
farther south, somewhere between I 69 and Saginaw Bay to begin the
day Tuesday.

Significant uncertainty exists on potential high temperatures for
Tuesday. Question comes down to how aggressive the backdoor marine
release will be Monday evening and the prevalence of clouds during
the daytime Tuesday. NBM 5.0 25th percentile suggests 40s for the
northern third of the cwa and lower to middle 60s south of M 59,
whereas the 75th percentile has middle 50s to lower 60s for the Tri
Cities/Flint and middle to upper 70s for Metro Detroit. The forecast
resides with cooler temperatures near Lake Huron and Saginaw Bay
with a northeast wind.

Merging of northern and southern stream upper level jet axes will
then force a frontal wave and surface low pressure reflection
through Lower Michigan late Tuesday night. There are a number of
concerns for the Tuesday night period.

1. Potential for isolated slippery spots due to freezing rain across
Midland and Bay counties and far northern Thumb. Tricky forecast
with regards to freezing rain potential for portions of Midland,
Bay, Saginaw, Tuscola and Huron counties Tues evening/night because
of the significant warm air advection that is forecasted to occur.
Model soundings show temperatures as warm as 13.5C at 2.7 kft agl
providing heat content to the rain droplets. There does appear to be
some feedback/contamination of Lake Huron ice cover on surface
temperatures immediately downstream of the Lake. There is low
confidence that the very shallow subfreezing layer will be able to
persist. The forecast continues to reside on the warm side and will
need to be monitored.

2. The potential for severe weather early Wednesday morning with
likely thunderstorm activity. Differences exist but both the
deterministic 3km NAM and the HRDPS support the surface warm front
lifting in vicinity of Washtenaw County and Metro Detroit between 07-
12z Wednesday. Forecast soundings support very strong static
stability for a greater portion of the forecast area, but neutral
stability to convectively unstable conditions will be possible along
and south of the front. Will need more CAM data inside of the window
to get a better handle on storm mode and potential severe weather
threats. At this point, a long hodograph and convective available
potential energy to 1000 J/kg suggests strong wind gusts/large
hail/and a tornado threat for those areas along and to the south of
the warm front. Legit surface low and nose to +50 knot low level jet
brings a strongly forced event. The latest Day 2 Outlook issued by
SPC has a Slight risk designation for severe weather south and west
of a line from Howell to Monroe and Marginal risk for much of the
area including, Saginaw, Port Huron and Metro Detroit.

3. Placement of heavy rainfall axis and QPF amounts. With the
significant warm air advection and low level jet forcing PWATS are
forecasted to reach 1.40 inches Wednesday morning which is at the
Daily Maximum for DTX raob data. NBM 5.0 data supports widespread
rain with the interquartile range between .75 inch and 1.75 inch
with highest amounts across the south. The biggest question is
whether or not a favorable corridor will set up for any training
convection. Need to get the event window with the CAM solutions but
collection of MPAS runs suggests convection will be relatively
progressive. WPC has designated all of the area as a Marginal Risk
for excessive rainfall.

Composite trough axis and associated absolute vorticity continues
height falls into the late Wednesday period. Model data supports a
period of deformation forcing that should result in a changeover to
snow for the evening period. The potential exists for a minor snow
accumulation across Bay and Midland Counties Wednesday evening and
melting snow for most areas.

Dynamic Pacific shortwave continues to be advertised for Lower
Michigan Friday. Depth of saturation, environmental profile of the
front, and projected UVVs through 700-500mb and the DGZ suggests
accumulating snow for a portion of the forecast area. PoPs currently
reside in the 50 to 70% range.

MARINE...

Southwesterly winds quickly restrengthen early this morning as a
second low slides along the far northern shore of Lake Superior.
Overall setup is similar to Sunday though with stronger warm
advection resulting in more neutral to stable overlake thermal
profiles. This further limits sporadic gale potential over central
Lake Huron with 25-30kt gusts more likely (20-25kt winds over the
rest of the region). A diffuse pressure gradient sets up across the
central Great Lakes by late today as the secondary low reaches
northern Quebec allowing winds to turn lighter through Tuesday.
Active pattern and stronger flow return by midweek as deepening
Plains low pressure tracks over the central/southern Great Lakes.

HYDROLOGY...

Widespread showers and thunderstorms will develop Tuesday night into
Wednesday as a low pressure system tracks northeastward across Lower
Michigan. Expected rainfall totals range from 0.75-1.75 inches by
Wednesday evening, followed by a changeover to melting snow from
north to south. Ensemble data suggests rises on area rivers will be
expected with a chance for minor flood stage for river systems.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421.

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

$$

AVIATION.....TF
DISCUSSION...CB
MARINE.......KDK
HYDROLOGY....CB


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