Ann Arbor, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

608
FXUS63 KDTX 261021
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
621 AM EDT Sat Jul 26 2025

.KEY MESSAGES...

- Multiple rounds of showers and thunderstorms are expected today
into tonight. A few storms could generate damaging wind gusts
however torrential rainfall and localized areas of flooding is the
primary hazard with storms today.

- Heat and humidity build Sunday and Monday as high temperatures
return to the lower 90s with heat index near 100 through early next
week.

&&

.AVIATION...

An ongoing influx of deep layer moisture in advance of upstream
short wave impulses will result in increasing coverage of showers
during the late morning into the afternoon. The ascent tied to a
little more amplified wave will be strongest during the afternoon,
coinciding with peak daytime instability. This will be the period
where thunderstorm potential will be greatest. Forced ascent may
linger into tonight across far southern Lower Mi, along a mid level
moisture and instability gradient. This may provide another round of
convection to the metro Detroit terminals late this evening into the
early portion of the overnight. Cloud bases are likely to remain
highly variable through the day. MVFR and IFR based stratus which
has been developing across the region early this morning should
experience some increase in the cloud bases with diurnal mixing.

For DTW/D21 Convection...While precise timing still carries some
uncertainty, there continues to be the potential for either
scattered convection or a cluster of convection to impact the
airspace from mid afternoon into the early evening hours.

THRESHOLD PROBABILITIES...

* Moderate in ceilings aob 5000 feet today and tonight.

* Moderate in thunderstorms this afternoon and evening. Low tonight.

&&

.PREV DISCUSSION...
Issued at 303 AM EDT Sat Jul 26 2025

DISCUSSION...

Active pattern continues today as a series of convectively augmented
shortwaves are set to stream into southern lower MI from the
Midwest. In the near term, the stalled frontal boundary over
Lenawee/Monroe continues to support squattered (thunder)showers for
areas south of I-96 early this morning. This activity shifts
northward over the course of the morning as the first shortwave
impulse over northern IL at press time begins to push into MI
forcing the frontal boundary back north as a warm front. Modest
developing LLJ (~25-35kts) behind the front leads to rapid moisture
transport into SE MI as surface dewpoints quickly reach the lower
70s by late morning- closer to mid 70s likely in the south. In terms
of PW climatology, this airmass is near/above the daily record as 2-
2.25" values overspread the region.

Lead shortwave and accompanying showers begin to vacate to our east
late morning/midday as the second, stronger mid-level wave
(currently over northern MO/KS at press time) arrives over the
state. A sizable subset of CAMs have begun converging on this wave
providing the greatest storm coverage of the day as it tracks across
SE MI. However these solutions still vary quite a bit with the
wave`s timing reaching the westernmost CWA areas, ranging from as
early as 14-15Z to as late as 18-19Z, owing to differences in
handling the ongoing convective influence/modification. The later
the arrival window, the more diurnal destabilization is able to
occur to push SBCAPE values toward 1500 J/kg supporting better storm
coverage as well as more rigorous updrafts. Shear isn`t particularly
impressive though the LLJ does support 0-6km bulk values near 30kts
focused towards the Ohio border. These southern areas (south of M-
59) are under a Day 1 marginal risk from SPC mainly for damaging
wind gusts. That said, main hazard with convection will be
torrential rainfall and flooding potential given the moisture-rich
airmass combined with warm cloud layers between 13-15kft. This
secondary wave shifts east of the area during the early evening
timeframe likewise shifting the wider spread convection to our east
with lingering showers/storms turning more scattered in nature.

Finally a third trailing MCV augmented shortwave then is set to
slide across the region late evening. The favored track is
near/along the IN/OH/MI border however some solutions like the NAM
Nest advertise slightly farther north over southern lower MI. The
exact track will determine the northward extent of additional rain-
as it currently stands I-69 looks to be the northern edge. This
portion of the event however carries high uncertainty and overall low
predictability as how much convection is even able to develop with
this wave is highly dependent on the progression and robustness of
earlier day showers/storms under to the first two shortwaves.

Drier conditions take hold by Sunday morning as weak surface high
pressure establishes itself over the central Great Lakes. First half
of the new week is dominated by a broad mid-upper ridging over the
CONUS east of the Rockies. SE MI resides on the northern edge of the
heat dome bringing a renewed multi-day period of highs in the upper
80s and 90s, dewpoints above 70F, and heat indices well into the 90s
to near 100F. Caveat is being on the edge of the ridge opens the
door for ridge-running MCS`s to track near or over the area
potentially influencing both actual and feels-liek temps.

MARINE...

Weak high pressure is now off to the east in Ontario, with light
winds ranging from SW to E within the diffuse pressure pattern left
behind. Main focus for today is the northward shift of the warm
front, which shifts winds to the southwest and draws warm/unstable
air back into lower Michigan. Shower and thunderstorm coverage is
expected to increase and expand northward through the day as several
disturbances ripple along the frontal zone. A few strong to severe
storms will be possible this afternoon-evening, with the primary
concern being wind gusts in excess of 40 knots and isolated large
hail to an inch. The severe threat wanes after midnight, but heavy
rainfall may continue through Sunday morning until high pressure
ushers in a drier airmass briefly for Sunday. Periods of showers and
storms continue into early next week followed by a pattern shift mid-
week as Canadian high pressure fills in from the northwest.

HYDROLOGY...

The stalled front lifts back north today as warm front ushering hot
and humid conditions back over the entire region. The anomalously
moist airmass overspreads the region while still carrying PW around
2" in addition to warm cloud depths supporting efficient rainfall
rates. A series of waves augmented by ongoing convection over the
Plains are set to slide over southern lower MI throughout the day.
Scattered showers/storms are possible this morning through the late
evening with greatest coverage looking to occur during the afternoon-
early evening period. Overall predictability for timing, location,
and duration of storms are low owing to the complex set-up however
confidence is high for torrential rainfall threats under any storms
today due to this moisture-laden airmass. Rainfall rates in excess
of 2"/hr are likely under the strongest storms (even weaker storms
will be capable of rates at or above 1"/hr). Localized flooding is
expected especially in urban and low lying/flood prone areas. More
impactful flooding is possible should storms train over the same
locations.

&&

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

$$

AVIATION.....SC
DISCUSSION...KDK
MARINE.......MV
HYDROLOGY....KDK


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