Ann Arbor, Michigan 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

338
FXUS63 KDTX 252303
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
703 PM EDT Sat Jul 25 2026

.KEY MESSAGES...

- Heat and humidity build back into the region Sunday-Monday with
  highs around 90 degrees and heat indices in the low to mid 90s.

- Isolated strong to severe thunderstorms Sunday evening/night, with
  a more organized severe weather threat arriving late Monday.
  Damaging winds are the primary hazard both days.

&&

.AVIATION...

SE Mi remains in a diffuse pattern between Atlantic coast high
pressure and low pressure slowly organizing from the central Plains
into central Canada. This has VFR clouds around 5000 ft increasing
over the northern Great Lakes, well ahead of the surface warm front
analyzed north-south along the MS river valley. This front is not
projected to move much toward Lower Mi tonight leaving the
expectation for low VFR ceiling to persist along the SE Mi terminal
corridor tonight, although MVFR ceiling will be monitored as it
extends from the upper Midwest into the lower Ohio valley late
tonight and Sunday morning.

Coverage and timing of potential thunderstorm activity is the
weather focus for Sunday. Predictability remains low, however it
does appear that nocturnal convection occurs mainly over the
northern Great Lakes late tonight and Sunday morning. That leaves a
chance for weakly organized development to occur just about anywhere
in SE Mi within an uncapped profile and as daytime heating builds
from late morning through the afternoon. This level of uncertainty
still supports holding off on a defined mention of storms in this
terminal forecast issuance in favor of later updates.

D21/DTW Convection... There is a low chance of thunderstorms Sunday
afternoon and evening. Confidence in coverage and timing remain low.

.DTW THRESHOLD PROBABILITIES...

* Moderate for ceiling 5000 ft or less Sunday morning.

* Low for thunder Sunday afternoon and evening.

&&

.PREV DISCUSSION...
Issued at 325 PM EDT Sat Jul 25 2026

DISCUSSION...

Influence of high pressure is waning this afternoon as amplifying
central CONUS ridging builds across the Midwest. This mid-upper
pattern shift allows a ridge running wave train to drop into the
central Great Lakes through the remainder of the weekend and Monday
offering multiple chances for storms locally.

Expansive coverage of stratus crossing Lake Michigan demarcates the
lead edge of the first of these shortwaves which is set to cross SE
MI this evening. Dry resident airmass in place (12Z KDTX RAOB showed
0.72" of PW) precludes any rain chances with the main consequence
instead being the initiation of moisture advection into southern
lower MI through tonight. Lower level moisture is established by
Sunday morning tied to the arrival a second wave offering the
chances for scattered showers and isolated thunder first over the
Saginaw Valley. Chances then shift south of the course of the
morning as the shortwave and the left exit region of an upper
Midwestern jet streak shift southeast. Some afternoon-evening
redevelopment remains possible from peak heating though better
convective signal comes late evening-Sunday night when northern MI
convection drops south into/near the area. Any storms that do manage
to develop in the evening stand the best shot at becoming strong to
severe with ~1000J/kg of MLCAPE still available and shear 35-40kts.
While instability partially wanes by time of any northern MI
convection reaches the area, shear holds unchanged maintaining
organization and isolated severe potential. Primary hazards would be
damaging wind gusts and locally heavy rainfall with hail being a
lesser secondary threat. All of SE MI is under a Marginal Risk from
SPC.

Model signal early Monday still muddled with mid-range solutions
highly varied in the degree of lingering morning showers/storms
which affects the magnitude of available instability late day. That
said, confidence is still higher, relative to prior waves, for
Monday evening/night in organized severe potential as a mid-level
trough digs into the northern Great Lakes. In addition to the
stronger synoptic kinematics, attendant surface cold front dropping
through the state also provides more robust forcing mechanism
resulting in good model agreement for MCS development. Its exact
placement/track however is the main point of uncertainty with a wide
range of outcomes currently advertised in the model suite ranging
from west MI to eastern Lake Huron. Given the convective mode,
severe wind gusts are the primary hazard with a low but non-zero
chance for a QLCS tornado. All of SE MI remains under a Day 3 Slight
Risk from SPC.

Low pressure peels east of the region by Tuesday leaving cooler,
drier airmass in its place as 850mb temps fall to lower teens C with
sub 60F dewpoints. Resultant midweek highs hold slightly below
average in the lower 80s including some upper 70s possible
Wednesday. Surface high pressure sinking out of northern Ontario
promotes clearer skies supporting another period of pleasant
weather.

MARINE...

Light southerly winds draw warmer air and greater instability into
the central Great Lakes leading to increasing thunderstorm activity
on Sunday, including the chance for a strong to severe storm Sunday
night. The primary low pressure system then tracks across the
northern Great Lakes during Monday. Thunderstorm activity continues
to increase coverage and intensity with this system, especially
along the trailing cold front that brings a chance of strong to
severe thunderstorms as it moves through the region. Outside of
storms, wind and waves are low until the northerly wind shift post
front late Monday night into Tuesday when speeds likely reach 25 to
30 knots over southern Lake Huron. If the low deepens enough over
the Eastern Great Lakes Tuesday evening, a short period of gales
could even come into play. Winds slowly diminish on Wednesday as
large area of high pressure over the Western Great Lakes slowly
advances east, arriving on Thursday. This will assure dry conditions
for those days.

HYDROLOGY...

Several rounds of showers and thunderstorms are possible Sunday into
early next week. An increasingly humid and unstable airmass will
lead to rainfall rates over an inch per hour in some thunderstorms.
Recent dry weather and low soil saturation will help mitigate
widespread flooding concerns, although localized flash flooding of
low-lying, urban, and other flood-prone areas remains possible if
thunderstorms repeatedly impact the same locations.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...None.
Lake Huron...None.
Lake St Clair...None.
Michigan waters of Lake Erie...None.

&&

$$

AVIATION.....BT
DISCUSSION...KDK
MARINE.......SF
HYDROLOGY....MV


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