008
FXUS63 KDTX 021406
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1006 AM EDT Wed Jul 2 2025

.KEY MESSAGES...

- Afternoon/evening thunderstorms will be possible each day today
through Friday (Independence Day).

- A Marginal Risk for severe weather is in place today north of I-94
and Thursday south of M-59. Isolated wind gusts to 60 mph will be
the main concern.

- Seasonable temperatures expected today and Thursday with a warm up
this holiday weekend. Temperatures Saturday and Sunday may exceed 90
degrees.

&&

.UPDATE...

500 MB shortwave trough axis arriving over the Central Great Lakes
late today/early this evening with 0-6 KM shear increasing into the
30-35 knot range will be supportive of storms, as MLcapes reach at
and above 1000 J/kg, particularly across the Thumb region, closer to
the mid level cold pool. However, mid level dry air currently in
place, with a significant speed bump/cap around 10000 feet makes for
an uncertain forecast with respect to coverage, and considered
lowering inherited pops. However, it appears the 700 MB temps at
both GRB and APX are bit colder than model initialization, and with
radar activity noted tracking into Western U.P, not going to adjust
the forecast. Southeast Michigan remains in marginal risk, mainly in
the 4-10 PM window, with isolated precip loaded wind gusts up around
60 mph. None-the-less, with the low wet bulb zero heights, marginal
hail up to 1 inch in diameter possible as well. Will be watching the
surface dew pts through the day, to see if we can mix down
significantly in the afternoon, which would help further limit
activity.

&&

.PREV DISCUSSION...
Issued at 738 AM EDT Wed Jul 2 2025

AVIATION...

Dry boundary layer will lead to prevailing VFR conditions today and
tonight. Disorganized shortwave energy streaming within a low
amplitude trough will bring weak synoptic scale lift to Southeast
Michigan during the afternoon. Midlevel cooling within the 7.0 to
13.0 kft will lead to higher based cumulus. Will maintain a Prob30
grouping for thunderstorms and KFNT and KMBS for continuity.

For DTW/D21 Convection...Thunderstorm chances this afternoon will be
greater north of the I 96.

THRESHOLD PROBABILITIES...

* Low for ceiling 5000 ft or less this afternoon.

* Low for thunderstorms this evening.

PREV DISCUSSION...
Issued at 405 AM EDT Wed Jul 2 2025

DISCUSSION...

Clear skies observed on satellite across the Great Lakes this
morning ensure a sunny start to the day for SE Michigan with
overnight lows in the low 60s right around normal for early July
standards. With the exception of the nocturnal stable layer, expect
this morning`s RAOB to look very similar to the 00z observation with
an inversion centered around 7.0 kft agl and deep layer stability
above that. Throughout the day, vertically stacked low pressure near
Hudson Bay will ease south to cool mid-levels especially over the
Tri Cities and Thumb regions. This ultimately leads to the
development of a narrow ribbon of instability and mid-level lapse
rates of 6-6.5 C/km that will be engaged by multiple weak shortwaves
this afternoon and evening. Scattered showers and thunderstorms will
develop in response to these features, with the greatest coverage
north of I-69. Given weak mid-level flow (less than 30 knots),
updrafts will struggle to organize on a widespread basis although
well-mixed/dry boundary layer conditions could lead to a few
instances of gusty winds as storms collapse. SPC has designated a
Marginal Risk of severe weather in the SWODY1.

The Hudson Bay low dives southeast overnight and drives a higher
amplitude trough and upper level jet into Lake Huron by Thursday
morning. At the surface, high pressure fills in from Canada to
establish a low level deformation axis overhead that will focus
shower/thunderstorm potential more toward southwest lower MI
Thursday afternoon-evening. Should see a sharp delineation to the
diurnal cumulus field which will be a proxy for surface-based
instability and thus thunderstorm potential. Temperatures will be a
few degrees cooler to the north/east of this boundary, but
ultimately all areas will see daytime highs in the 80s on Thursday.
With the stronger synoptic wind field in place (35-60 knots spanning
SE Michigan), any thunderstorms that do form could become organized
but coverage does not look all that high in the latest hi-res
output. SPC has also designated a Marginal Risk of severe weather in
the SWODY2.

Friday marks the beginning of a pattern transition to a warmer and
more humid airmass as the ridge over the Intermountain West begins
to fold into SE Michigan. Throughout the day Friday, this ridge
builds to ~594 dam while veering wind profiles locally suggest the
beginning of warm advection into the area. Building heights aloft
help strengthen the surface anticyclonic circulation, which will
have potential to completely clear out instability from SE Michigan
for Friday. NBM PoPs highlight the more bearish solutions (00z Euro)
that clear out the instability completely to support a dry
Independence Day. However, there still are bullish solutions (00z
GFS/NAM) that draw the warm front back into the area by Friday
afternoon. The drier Euro solution would result in warmer daytime
highs for the holiday as well, in the mid to upper 80s, which would
be tempered if convective cloud can develop.

The ridge will push fully overhead this weekend which results in
another round of hot and humid conditions for SE Michigan. A dry
forecast for Saturday can be attributed to the strong subsidence
signal near the ridge axis. Temperatures both Saturday and Sunday
will have potential to exceed 90 degrees while heat indices reach
the mid-90s.

MARINE...

A ridge of high pressure extends from the Midwest into the Great
Lakes, promoting stable conditions and southwest wind around 10 to
15 kt early today. Chances for scattered showers and thunderstorms
increase through the afternoon as a weak cold front approaches from
the north by this evening. Most showers and storms will be focused
across Lake Huron, and isolated storms will be capable of producing
winds in excess of 40 kt and hail. Post-frontal wind organizes out
of the northwest on Thursday, remaining light. High pressure builds
directly across the region Thursday night to maintain light wind and
waves into Friday. A warm front then lifts across the region on
Saturday, setting up a breezy southwest flow that brings in warmer,
more humid, and unsettled conditions for the weekend.

&&

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

$$

UPDATE.......SF
AVIATION.....CB
DISCUSSION...MV
MARINE.......TF


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