460
FXUS63 KDTX 181901
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
301 PM EDT Sat Oct 18 2025

.KEY MESSAGES...

- Widespread rain will affect the area tonight and Sunday. Rainfall
amounts are forecast to range from a half inch up to 2 inches, with
some higher amounts possible around the tri cities.

- Scattered thunderstorms will occur tonight. There is an isolated
damaging winds will the main threat.

- Wind gusts of 30 to 40 MPH are possible on Sunday.

- Much cooler air will settle into the region by mid week.

&&

.DISCUSSION...

Rapid amplification of the long wave trough over the northern plains
will occur tonight into Sunday as it dives into the Mid Mississippi
and Lower Ohio Valley region. This will allow the short wave now
over Oklahoma to rapidly be ejected northeast toward the Great Lakes
region late tonight. Model solutions indicate a plume of seasonally
high precipitable water values being advected into the Great Lakes
region tonight in advance of this lead short wave. Rapidly falling
mid level heights and strongly divergent/difluent upper level flow
across the nrn Ohio Valley and Lower MI will contribute to rapid sfc
cyclogenesis as the forecast sfc low track from nrn Indiana tonight to
northern Lake Huron by late Sun morning (projected to deepen to
around 988mb). There are several 12Z model solutions which develop a
secondary sfc low along the associated cold front over Se Mi Sun
morning. The main implications of this solution would be a slower
fropa.

Weak instability will advect into Se Mi from the southwest this
evening, possibly leading to some convective initiation as mid level
capping weakens. A strengthening frontogenetical response in the low
to mid levels will then take hold late in the evening across the
northern portions of the forecast area associated with the deepening
long wave trough and rapidly strengthening upper jet dynamics. The
mid level front/deformation axis is forecast to intensify during the
night. The deformation axis is forecast to hold nearly quasi
stationary tonight before transitioning eastward across the area on
Sunday as the long wave trough slowly progresses across the Great
Lakes and Ohio Valley. The strength of the ascent combined with
precipitable water values surging to 1.5 inches and influxes of weak
mid level instability will result in widespread rain with embedded
thunderstorms tonight/early Sun morning. More or less light to
moderate rain is then expected Sunday afternoon as the mid level
frontal dynamics slowly exit to the northeast. There is strong
support for a swath of 2 to 3 inch total rainfall amounts within the
region of most persistent forcing. Probabilistic guidance suggest
this is more likely to occur across the Saginaw Valley region to
perhaps locations west of the US-23 corridor. Outside of this
region, rain totals are likely to be under two inches, with some
potential for less than an inch across the far eastern third of Se
Mi. With the highest rain totals more likely outside of the urban
Detroit corridor and in light of recent dry conditions, no flood
watch is planned with the afternoon package.

In addition to the rain, low level wind fields will be quite strong
with this system. Based on the forecast position of the sfc front,
the eastern half of the forecast area will be in the warm sector Sun
morning, with 40 to 50 knot southerly winds above 1k feet. Model
soundings indicate some degree of stability in the boundary layer,
which is expected to keep the wind gusts below advisory levels. Post
frontal west-northwest winds will be rather gusty as cold air
advection deepens the mixed layer. Model soundings and probabilistic
guidances keep these winds sub advisory level as well.

Ridging through the low to mid levels will then expand across the
region Monday, leading to dry but cool conditions. Mid level trough
amplification is then forecast to evolve into a closed mid level low
over the Great Lakes Tuesday. This system will not have much
moisture to work with but the forcing will still be worthy of a
chance of light rain. Much colder air does get advected into this
system, enough to support some lake effect clouds/rain showers into
Wednesday.

&&

.MARINE...

Low pressure system is rapidly deepening over the mid-Mississippi
Valley and will track across Lake Huron Sunday morning. Very strong
flow just off the surface (50kts) will accompany the eastern flank
of the system. Furthermore, the near surface pressure gradient
forcing will support sustained winds approaching 30 knots across
most of the region. There appears to be enough differential thermal
advection to neutralize the boundary layer over Southern and Central
Lake Huron, which will support occasional gale gusts in the
south/southeast flow during the morning. Elsewhere, the higher
momentum will support Small Craft Advisory conditions prior to the
abrupt flip of the flow to northwest as the system passes.

More widespread gale potential exists Sunday afternoon and evening
as colder air rushes in allowing for deeper mixing across the
region. However, the flow in the lower atmosphere is not expected to
be as quick as observed in the warm sector. Nevertheless. gale gusts
are expected across most of Lake Huron, including Saginaw Bay. The
strongest flow should occur over northern Lake Huron where 40-45kt
flow aloft supports potential surface wind gusts in the 35-40kt
range - aided additionally by some shoreline channeling influences.

Another strong system will follow quickly on Tuesday. The resident
cooler airmass preceding the arrival will support greater mixing
potential upon entry - likely resulting in a band of southwesterly
gales. Guidance is presenting a few different answers right now
regarding the storm track and deepening sequence - so expect a fair
amount of adjustment to the forecast over the next day or two.

&&

.HYDROLOGY...

Deepening low pressure will track across the region tonight into
Sunday. This system will drive a high amount of moisture into the
region for mid October. The result will be widespread rain with some
embedded thunderstorms. 24-hour rainfall totals ending Sunday
afternoon are forecast to be in the 1 to 2 inch range. Probabilistic
guidance suggests some lower totals possible across the far eastern
portions of the area from downtown Detroit to Port Huron, with some
higher totals possible across the tri cities region. With some
convective potential, three hour conditions convective rain
probabilities of a half to three quarters of an inch are moderate to
high overnight through Sunday morning. In light of recent dry
conditions, this rainfall is not expected to cause significant
flooding. There is also relatively high probabilities that the
heavier rain will occur northwest of the urban Detroit area,
limiting the risk of urban flooding.

&&

.PREV DISCUSSION...
Issued at 1232 PM EDT Sat Oct 18 2025

AVIATION...

Broken line of showers to stall out over over southeast Michigan,
particularly across PTK/FNT.  Renewed shower and possible strong
thunderstorm activity expected late in the day and evening hours.
Widespread coverage of showers developing tonight with possible
embedded strong thunderstorms. This activity will support low MVFR
cigs, with a period of IFR Sunday morning in heavier activity and
embedded in the surface low/cold front tracking through. A very
strong low level jet (50-60 kts at 4 kft) tracks through late
tonight into Saturday morning, but uncertainty with just how much of
the strong winds mix down to the surface. Southern tafs look to have
the strongest southerly winds, gusting at least around 30 knots.
During the afternoon when winds shift to the west-northwest, all
sites should see winds gusts aoa 30 knots by late afternoon.

For DTW/D21 Convection...Potential exists for isolated thunderstorms
to develop late this afternoon and evening. Embedded thunderstorms
will remain possible as rain increases in coverage overnight into
Sunday morning ahead of a cold front.

DTW THRESHOLD PROBABILITIES...

*  Low for ceilings below 5kft this afternoon through early tonight.
   High late tonight into Sunday.

*  Low for thunderstorms late this afternoon though Sunday morning.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 5 AM Sunday to 5 AM EDT Monday for LHZ443.

     Gale Warning from 2 PM Sunday to 2 AM EDT Monday for LHZ361-362.

     Gale Warning from 8 AM Sunday to 2 AM EDT Monday for LHZ363-462-463.

     Small Craft Advisory from 8 AM to 3 PM EDT Sunday for LHZ421-422-
     441-442.

     Gale Warning from 3 PM Sunday to midnight EDT Sunday night for
     LHZ421-422-441-442.

Lake St Clair...Small Craft Advisory from 5 AM Sunday to 5 AM EDT Monday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 5 AM Sunday to 5 AM EDT Monday for LEZ444.

&&

$$

DISCUSSION...SC
MARINE.......Mann
HYDROLOGY....SC
AVIATION.....SF


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