812
FXUS63 KDTX 191207
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
807 AM EDT Thu Jun 19 2025

.KEY MESSAGES...

- Light to moderate rain continues this morning with better coverage
across the Tri-Cities and northern Thumb. Additional chances for
showers and thunderstorms this afternoon and evening.

- Chance (20-40%) for showers and thunderstorms again Friday and
Saturday.

- Hot and dry Sunday and Monday. High temperatures in the 90s and
heat index around 100 are likely, with minimal relief at night.

&&

.AVIATION...

Variable MVFR to IFR ceilings continue into the early afternoon and
as low pressure system lifts further to the northeast and a cold
front works southeast. Scattered showers will persist through this
morning as well and gradually taper off throughout the afternoon.
Isolated embedded thunder will be possible. Colder and dry air will
accompany this front and swing winds out of the northwest and
maintain gusts to around 20 knots. Conditions improve to VFR this
afternoon and carry through tonight.

For DTW/D21 Convection...Isolated thunderstorms will be possible
into early this afternoon. Confidence too low to mention in TAFs.

 THRESHOLD PROBABILITIES...

* High for ceiling aob 5000 ft through this morning and early
  afternoon.

&&

.PREV DISCUSSION...
Issued at 320 AM EDT Thu Jun 19 2025

DISCUSSION...

An area of deformation aligning with wrap around moisture from the
departing low pressure system will continue to support widespread
light rainfall through the Tri-Cities and northern Thumb. Isolated
to scattered coverage will be possible for locations south. The lack
of instability will hamper thunderstorm chances, keeping rainfall
rates in check, but the prolonged rainfall across the Tri-Cities
will produce an additional half-inch to inch of new accumulation
leading into the late morning hours. The continued departure of the
low will back flow and release the residual moisture into Southeast
Michigan ahead of a trough axis which will expand light rainfall
across the greater portion of the cwa through the late morning and
early afternoon hours.

Advection of moisture out of the state will bring a window in
the late afternoon to early evening for destabilization which will
renew chances for some isolated to scattered coverage of showers or
thunderstorms. The CAPE gradient along the the edge of the departing
cloud shield can lead to a differential heating gradient and may
serve as a mesoscale trigger for CI. Degree of organization will
depend on magnitude of instability recovery from morning
precipitation, but at this time HREF P(>500 J/kg CAPE) nears 100%
through the Tri-Cities, as scouring of cloud cover takes place from
west to east. While severe weather is not anticipated with afternoon
and evening activity, EBWD values of 20-25 knots can support some
degree of organized convection and steep low-level lapse rates with
DCAPE value around 800 J/kg can aid in 45-55 mph gusts from a
microburst.

All storm chances end late tonight with the lack of diurnal heating,
with some additional showers and thunderstorm chances again for
tomorrow afternoon through Saturday morning along an elevated warm
front front that accelerates in on the nose of a mid-level jet.
Tomorrow through the weekend will see the enhancement of a
significant upper-level ridge that will become the dominant feature
of interest through early next week with strong multi-model ensemble
support for anomalously high mid-tropospheric heights and
temperatures.

The EPS show 500mb heights reaching or exceeding the 99.5th
percentile over SE MI Sunday into Monday and likewise with 850mb
temperatures nearing or exceeding the 99.5th percentile as 850mb
temperatures rise aoa 22C. It is worth noting that the ECMWF and
corresponding ensemble solutions may be amplifying the forecasted
ridge somewhat noting the warm biases observed from last year, but
regardless, strong agreement among GEFS members in conjunction with
the EPS suite lends to an extremely high confidence forecast for the
expansion of well above normal temperatures through early next week.

850MB temperatures aoa 22C along with dry conditions will allow
temperatures to reach the 90 degree mark Saturday, and exceed the 90
degree mark Sunday and Monday, with mid 90s possible for much of the
cwa, especially through the urban corridor. Dew points in the upper
60s to low 70s will bring oppressive humidity and will allow heat
indices to rise into the upper 90s to low 100s Sunday and Monday.
EPS EFI values for max temperatures reach .9-.99 both days, with
shift of tail values near or above 1 through the urban corridor and
portions of the Tri-Cities and Thumb. This highlights a notable
displacement (upper 10%) of ensemble solutions when compared to M-
Climate data and reinforces that hot temperatures are inbound,
potentially challenging  prior records. Last, this heat wave will
also bring very warm overnight low and will provide no relief as
forecasted lows hold in low to mid 70s Sunday morning through Tuesday
morning. Another round of 90 degree temperatures are possible
Tuesday afternoon, but the introduction of rain chances lowers
confidence in forecast trends.

MARINE...

Small Craft Advisories take effect today for outer Saginaw Bay to
Harbor Beach, and for Lake St Clair and Lake Erie, associated with
wind and waves trailing the governing low pressure system as it exits
the region. An active shower and storm pattern continues through the
end of the week while gradually shifting farther north across the
Great Lakes while heat and humidity build across the region during
the weekend.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT this afternoon for LHZ421-441.

Lake St Clair...Small Craft Advisory until 10 AM EDT this morning for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EDT this morning for LEZ444.

&&

$$

AVIATION.....AA
DISCUSSION...AM
MARINE.......BT


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