548
FXUS63 KDTX 160759
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
359 AM EDT Wed Jul 16 2025

.KEY MESSAGES...

- Shower and thunderstorm chances increase midday with isolated
  strong to severe wind gusts and potential for heavy rainfall
  through this evening.

- Areas north of I-69 could see some additional storms late tonight.

- A cold front works through Thursday producing some additional
  morning showers/storms, then cooler and less humid air filters in
  through Friday.

- Additional storms possible Saturday with temperatures near seasonal
  normals.

&&

.DISCUSSION...

Clouds fill in aloft through the morning hours as Southeast Michigan
resides downstream of remnant nocturnal perturbation lifting in from
the Ohio Valley. This releases a stalled frontal boundary near the
MI/OH border, spilling north across the rest of southern Lower
Michigan as a warm front. The elevated portion was on the move as of
06Z as a cluster of showers/storms blossomed on KDTX radar near the
western I-94 corridor, demarcating the 925-850 mb portion of the
frontal slope. Forecast soundings indicate a somewhat unfavorable
column for persistence with this first wave as it outruns necessary
moisture.

Mid-level cooling, albeit limited, coupled with the advection of a
richer ThetaE environment from the south, leads to building
instability through the morning hours. Temperatures quickly rebound
after a mild night while dewpoints spike above 70F within the
expanding warm sector. This quickly translates to +1000 J/kg of
SBCAPE before noon, then ensemble mean SBCAPEs indicate further
rises this afternoon through diurnal heating (1250-1750 J/kg).
Although instability parameters should be more than sufficient for
scattered to perhaps numerous thundershowers, shear will be lacking.
Probabilities for 20+ knots of 0-6 km shear are quite low through
this evening. Severe thunderstorm coverage should therefore remain
more isolated in the absence of substantive dynamic support aloft,
but CAMs highlight broad coverage of single-cell storms through the
day. Heavy water-loading in the more robust updrafts could produce a
few microbursts capable of marginally severe wind gusts. Latest SPC
DY1 outlook maintains Marginal Risk across Southeast Michigan. PWATs
appear to spike over Metro Detroit which exhibits the highest
conditional QPF probabilities and resultant potential for isolated
urban/small-stream flooding (see Hydrology section for more info).

After an evening lull, a more convincing corridor of height falls
translates into Lower Michigan overnight, on the nose of a longer
wavelength trough axis. This shortwave accelerates across Iowa
before shearing into the upper Midwest. This provides meaningful
background ascent while an elevated mixed-layer tries to hold shape,
especially north of I-69. A more substantial wind field accompanies
this wavelet which increases potential for some linear organization
and a low-end nocturnal damaging wind threat, late tonight.

Active pattern continues Thursday morning as a cold front drops
through the Great Lakes, from the northwest. Timing has sped up a
bit which signals renewed convection is now more likely to flare up
within a less favorable environment. Progs indicate the frontal
boundary should clear east as early as 15Z, with weaker post-frontal
activity in-trail. CAMs are extremely bearish regarding storm/QPF
potential in the wake of the front, therefore made significant
revisions to automated NBM PoPs, lowered from Likely to Slight
Chance after 18Z Thursday. A bit breezier during the afternoon as
cooler Canadian air filters in. Comfortable Thursday night with lows
dipping into the 50s, outside of Metro Detroit.

Subjectively pleasant on Friday with highs largely in the 70s and
dewpoints in the 50s as a sub-700 mb anticyclonic gyre works east
across the Great Lakes. Energetic belt of zonal flow aloft persists
through the weekend and into early next week while surface high
pressure eventually moves into the Mid-Atlantic. This leads to a
return flow setup for the local area with rising dewpoints and 2 m
temperatures, although highs should hold near-normal. Potential
exists for showers and storms Saturday as several upstream wave
interactions take place, and MCS remnants flow into the region.

&&

.MARINE...

Increasing low level moisture today and daytime instability will
produce numerous showers and thunderstorms in the afternoon. Some of
the thunderstorms could be strong, producing localized wind gusts in
excess of 45 knots. Scattered-numerous showers and thunderstorms
likely persist Wednesday night, as low pressure and associated cold
front race east, passing through the Central Great Lakes Thursday
morning. North-northwest winds behind this system will likely top
out briefly in the 20-25 knot range over Lake Huron, which will
bring a chance of waves of 4 feet or greater to clip the nearshore
waters by Thursday evening. There may be just enough of an offshore
component to prevent small craft advisories however.

Winds veer around to the north-northeast Thursday evening, but
should be 15 knots or less by that time, with light and variable
winds for Friday as a large area of high pressure encompasses the
Great Lakes region.

&&

.HYDROLOGY...

Low pressure tracking into the Great Lakes/Ohio Valley brings
chances for scattered showers towards the Ohio border this morning
before scattered to numerous showers and storms develop this
afternoon. An increasingly humid airmass settles over the region
with surface dewpoints in the lower 70s and PWAT values of 1.75 to
2.00 inches. Overall setup is favorable for locally heavy rain with
any thunderstorm given ample moisture and a deep warm cloud layer
increasing precipitation efficiency. Very weak background wind field
will yield slow storm motions during the day with rainfall rates of 1-
2 in/hr expected. Some storms will lead to isolated areas of minor
flooding in low-lying/flood prone areas.

&&

.PREV DISCUSSION...
Issued at 1208 AM EDT Wed Jul 16 2025

AVIATION...

A weak shortwave slowly migrating northeast across MO/IL/IN will
lift across far southeast Michigan on Wednesday. This lead pocket of
energy aloft will help mid-level cloud spread into the area, but it
may not be enough to overcome the drier air in place over the area
late this evening. Thus confidence is waning as to whether or not
this first round of showers and storms will develop or maintain
itself later this morning. Later this afternoon, instability is
expected to build and should support widely scattered shower and
storms. Late Wednesday night, the delaying area of storms moving
across central Michigan may hold together enough to bring a few
storms to MBS/FNT.

For DTW/D21 Convection...Confidence is waning regarding the initial
round of showers and storms moving into the D21 airspace between 10-
15Z. Still expect scattered slow moving showers and storms around
during the afternoon and evening hours after 18Z.

THRESHOLD PROBABILITIES...

* Low to Moderate for thunderstorms after 18Z Wednesday.


&&

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

$$

DISCUSSION...KGK
MARINE.......SF
HYDROLOGY....KDK/KGK
AVIATION.....JA


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