639
FXUS63 KDTX 011729
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
129 PM EDT Thu Oct 1 2026

.KEY MESSAGES...

- Coverage and intensity of showers increase across SE Michigan
tonight.

- There is a chance for locally heavy rainfall until showers end
with the passage of a cold front Friday morning.

- Low temperatures are projected to reach the mid to upper 30s north
of metro Detroit by Saturday morning.

- Cool temperatures continue through the weekend.

- There is a low chance for a short period of light rain Sunday.

&&

.AVIATION...

Stream of Gulf moisture ahead of a cold front and passage of this
front will maintain widespread rain across KMBS through the evening
and will increase coverage across all other TAF sites tonight. MVFR
to IFR cigs are expected with the onset of rain showers along with
likewise restrictions to visibility under the more moderate rainfall
intensity. There will be a low chance immediately along the front
for acute stronger rain showers within a 1-3 hour window that can
bring very brief periods of LIFR cigs. Otherwise, winds will quickly
back from southwest to northwest after the passage of the front with
rapid dry air advection bringing quick improvements to ceiling
heights in the wake of the front.

D21/DTW Convection...Low potential for thunderstorms through this
forecast period.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet this evening.

* Low for thunderstorms this evening and overnight.

&&

.PREV DISCUSSION...
Issued at 434 AM EDT Thu Oct 1 2026

DISCUSSION...

Significant tropospheric moistening was sampled via the 01.00Z KDTX
RAOB, marked by vertical continuity in saturation and a measured
PWAT of 1.70 inches. This modified tropically sourced air mass has
allowed overnight showers to percolate with ease beneath sustained
perturbed flow aloft. The latest forcing mechanism has been
attributed to a series of shortwave impulses positioned ahead of an
inbound longwave trough moving eastward over southern Canada, and
downstream of a southern CONUS closed low. The southern wave has
been responsible for the influx of eastern Pacific and Gulf
moisture, upholding the appropriate environment for this extended
period of rainfall.

The low-level jet moisture connection is fully engaged early this
morning, with both increasing magnitude (30+ knots) and trajectory
continuity. Latest progs indicate the confluent stream arcs back to
Texas where the remnants of Hurricane Polo merge with Gulf-wide
theta-e advection. Additionally, the two synoptic waves will begin
to phase during the PM hours, leading to a rise in upper-level
divergence and local theta-e convergence. This lends continued
concern for the localized risk of heavy rainfall later today,
especially as a cold front extending from the northern system tracks
southeastward across Lower Michigan. The period of greatest concern
will be as the frontal slope engages the peak in low-level moisture
transport late this afternoon into the evening timeframe,  while the
system`s deformation axis centers overhead. See the Hydrology
section for additional details.

Latest NWP suite indicates peak 3-hourly rainfall rates between 00Z
and 06Z tonight as the front pushes through. Winds flip
northwesterly immediately behind the surface front tonight, although
showers will be slower to clear. Once aggressive post-frontal system-
relative isentropic downglide builds in, rainfall will quickly
conclude. Dry weather is then forecast by mid-morning Friday as the
Great Lakes reside downstream of building 1028 mb high pressure
moving into the Upper Midwest. Seasonably cool and dry as the ridge
dominates. A clipper system could bring a few sprinkles through
Sunday morning, while thermal troughing persists. 850 mb
temperatures crater early next week, with sub-0C values possible.
Morning frost concerns may arise should lows drop into the upper 30s.

MARINE...

Southwesterly winds will continue out ahead of an approaching cold
front, which arrives and stalls over southern Lower Michigan today.
With warm advection leading to more stable profiles and showers
moving through during this timeframe, wind gusts are expected to top
out only around 25 knots. With the front hung up until night, the
post frontal cold advection now looks slower; thus, the potential for
northwest wind gusts reaching or exceeding 25 knots looks to be late
in the day on Friday as 850 MB temps lower into the mid single
digits by Friday.

A large area of high pressure then builds in behind the departing
cold front on Friday into Saturday. This will bring lighter winds
for the first half of the weekend. A stronger low tracking through
the northern Great Lakes for the second half of the weekend brings
another opportunity for winds to reach or exceed 25 knots over Lake
Huron.

HYDROLOGY...

A mid to late week rainfall episode continues today, peaking this
evening and early tonight. It occurs as tropical moisture streams
into Lower Michigan, along and ahead of an approaching Midwest cold
front. A more persistent band of rain is established across the area
this afternoon as the cold front moves through the region by
tonight, when moisture parameters peak. High confidence in rainfall
totals up to 1 inch and medium confidence in totals over an inch.
The low-end chance for system rainfall totals to reach 2 inches
requires a slower frontal passage, leading to a longer window for
persistent rainfall. The chance exists for minor flooding of low-
lying areas and ponding on roads across the region until the rain
quickly ends post-front Friday morning.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 10 PM this evening to 10 PM EDT Friday
     for LHZ421-443.

     Small Craft Advisory from 10 PM this evening to 4 AM EDT Saturday
     for LHZ441-442.

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

$$

AVIATION.....AM
DISCUSSION...KGK
MARINE.......SF/SS/KGK
HYDROLOGY....KGK


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