914
FXUS63 KDTX 150950
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
550 AM EDT Tue Jul 15 2025

.KEY MESSAGES...

- Sunny and warm today with high temperatures around 90 degrees and
  heat indices in the low 90s.

- Shower and thunderstorm chances begin Wednesday and increase
  Wednsday night through Thursday with potential for heavy rainfall.

- A cold front sweeps through the area Thursday night followed by
  cooler and less humid air to start next weekend.

&&

.AVIATION...

Canadian wildfire smoke lingers across portions of Southeast
Michigan this morning offering additional periods of MVFR visibility.
HRRR/RAP smoke models show limited improvement in near-surface smoke
concentrations throughout most of the day. This is likely due to
persistent subsidence and weak surface flow which keeps cleaner air
at-bay until later this evening. Opted for prevailing MVFR HZ at all
terminals until this evening. Light surface winds organize out of
the south and should eventually slowly push the plume toward the
north. Smoke concentrations then improve which leads to an eventual
recovery in visibilities across the TAF sites. Weak winds expected
again overnight with increasing VFR cloud aloft (from south to
north), heading into the early morning hours on Wednesday.

For DTW/D21 Convection...Upstream convection late tonight into
Wednesday should largely weaken before reaching the airspace, but
expect ceilings to fill in through the mid-upper levels. VFR showers
are possible after 12Z Wednesday, thus TEMPO -SHRA.

THRESHOLD PROBABILITIES...

* Low for thunder after 12Z Wednesday.

&&

.PREV DISCUSSION...
Issued at 357 AM EDT Tue Jul 15 2025

DISCUSSION...

Weak high pressure is centered over Lower Mi to start the day and
begins more of an eastward move this afternoon and tonight. In the
meantime, it combines with a plume of deep dry air aloft to ensure
one more dry weather day across the region. Calm to light west wind
surface through mid levels backs and increases from the south, and is
expected to displace the forest fire smoke layer that had an
impressive impact on temperatures yesterday. Full sun then helps
readings reach guidance highs around 90 while surface Td lingering in
the 60s keeps humidity in the moderate range. Heat index projections
only tack on a couple degrees through peak heating.

Progression of the larger scale pattern gains traction tonight as
northern Ontario low pressure develops along the broad frontal zone
reaching from northern Quebec to the upper Midwest and then into the
central Plains. This system starts a weak process of low to mid
level moisture transport from the Ohio valley and pulls the surface
front back into Lower Mi late tonight and Wednesday morning. A
hybrid short wave/MCV also moves up from mid MS/TN valleys to
provide of boost of forcing, mainly south of the Mi border through
sunrise. The lack of anything resembling a low level jet otherwise
limits the northward reach of showers/storms in Lower Mi and reduces
effectiveness of the mid level theta-e gradient through Wednesday
morning. After that, the 15/00Z HREF advertises a more pronounced
flare-up of surface based convection across SE Mi during afternoon
peak heating as warm sector Td rises back into the 70s. The 70s Td
footprint also outlines coverage of PW rising into the 1.5 to 2 inch
range indicative of the moisture depth favorable for slow moving
convection capable of heavy rainfall with a few moisture laden
downbursts possible.

The Wednesday phase of events in the Great Lakes helps set the
larger scale moisture axis in place ahead of the Midwest frontal
system by Wednesday night. Convection ongoing upstream late tonight
runs the length of the front from western Lake Superior into the
Rockies. This supports the 15/00Z deterministic models that offer
broad agreement on similar cycles of surface based storms refiring
each afternoon as the frontal system moves closer to Lower Mi. Timing
is set for Wednesday afternoon activity across the Midwest to reach
SE Mi late Wednesday night into Thursday morning, and then flare up
again as the front moves through the region during Thursday.
Convective clusters arrive with nocturnal timing affecting lower
downstream instability but with an incrementally improved wind
profile. This is highlighted by model 500 mb wind increasing from sub
20 knots Wednesday afternoon to around 35 knots Thursday morning, in
line with the SPC marginal risk through 12Z Thursday.

Model consensus on the frontal passage Thursday night, before
midnight, is 6-12 hrs faster than the last few forecast cycles.
Surface high pressure is then building solidly into Lower Mi by
Friday morning with cooler and less humid air, but also giving way
to the next low pressure system more quickly during the weekend.

MARINE...

Light, mostly southerly winds, continue into Wednesday supporting
warm temperatures and increasing moisture. The next chance for
showers and thunderstorms will enter Wednesday through early Friday
as a series of upper-level disturbances and cold front pass over the
Great Lakes. This brings the chance for some localized stronger wind
gusts with any thunderstorm development, but otherwise winds remain
light given the weaker pressure gradient in place.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....KGK
DISCUSSION...BT
MARINE.......SF


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