882
FXUS63 KDTX 171748
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
148 PM EDT Tue Jun 17 2025

.KEY MESSAGES...

- Hot and humid today through mid-week.

- Small chances for showers and thunderstorms later today into
  Wednesday morning.

- Slight to Enhanced Risk for severe storms Wednesday afternoon into
  the evening. All hazards are in play including damaging winds,
  large hail, heavy rain and a few tornadoes will be possible.

- Storm chances Thursday and Friday into Saturday. Even hotter and
  humid conditions over the weekend as temperatures push 90 degrees
  and above.

&&

.AVIATION...

Expanding coverage of lower VFR cumulus continues this afternoon as
moderate SW flow brings warm and increasingly humid air into the
Great Lakes. This occurs ahead of low pressure in northern Ontario
that also pulls a cold front into Lower Mi which is expected to
stall near the FNT to MBS area tonight. Isolated thunderstorm
potential lingers late this afternoon and early evening toward the
PTK to DTW area then shifts toward FNT and MBS along and north of
the cold front later tonight. Borderline MVFR stratus is likely
along and near the stalled front and also in the warm sector late
tonight and Wednesday morning.

For DTW/D21 Convection...There is a slight chance (~25%) for an
isolated thunderstorm favored in the evening hours.

THRESHOLD PROBABILITIES...

* Moderate for ceiling aob 5 kft this afternoon through Wednesday
  morning.

* Low for thunderstorms late today and this evening.

&&

.PREV DISCUSSION...
Issued at 457 AM EDT Tue Jun 17 2025

DISCUSSION...

Deeper southwest flow kicks in today and will inject more warm and
moist air into Michigan. Temperatures at 850 mb climb to around 17C,
which will support a rather warm day with high temperatures into the
upper 80s. The extra moisture will also make for a very muggy day as
mid to upper 60s dewpoints lift into southeast Michigan. A mid/upper
wave with associated surface low pressure will be tracking northeast
out of Lake Superior across Ontario throughout today. This will draw
a cold front across Lake Michigan this morning and into central
lower Michigan this afternoon and evening. Instability ahead of this
front will be formidable SBCAPE to around 1000 J/kg, but deep layer
shear will be lacking greatly. Many CAMs are not generating much in
the way of convection through this afternoon as the front approaches
southeast Michigan. Will maintain the inherited ~25 pct PoPs given
the available instability and presence of the front. Timing is
focused across Saginaw Valley/Thumb and perhaps down to the I-69
corridor this afternoon into the early evening. Confidence is not
high for this activity. Any convection that is able to develop would
be more pulse type convection given the lack of shear and any strong
updrafts that can gain traction would be capable of isolated strong
winds.

Cold front is expected to stall out across southern lower Michigan
late this evening providing a focus for the next round of
convection. The activity late this evening/tonight will have better
PV advection driving a concentrated area of showers and
thunderstorms into southwest lower Michigan that may eventually
follow along the front into southeast Michigan. Models maintain some
instability while deep layer shear becomes better tonight. PoPs of
25 to 30 pct look good for now. Expectation is for this activity to
be sub-severe, but may require some monitoring.

Greatest focus remains on Wednesday into Wednesday night and the
potential for severe weather including damaging winds, large hail,
heavy rain, and tornadoes. Frontal boundary will again be the focus
for convection through Wednesday as a potent shortwave and a
deepening surface low tracks along the front through central Lower
Michigan some time Wednesday evening. There remains some differences
in timing of the low and placement of the frontal boundaries, but
several models are converging on the more bullish outcome in regards
to severe weather. The stalled frontal boundary will lift northward
as a warm front preceding the low during the day. A very moist
(dewpoints to 70 degrees/PWATs > 1.75 inches), unstable (MLCAPE 1000-
1500 J/kg/SBCAPE 2000+ per RAP), and favorably sheared environment
(40-50 knots of 0-6km bulk shear/20-30 knots of low level
shear/curved low level hodographs) will be in place in the warm
sector. The 00Z suite of CAMs remain split on Wednesday afternoon
activity along the warm front as the nose of the 50-60 knot LLJ
impinges on the CWA. Any activity that can initiate along the warm
front will be worth monitoring for severe potential. The greatest
severe threat lies late Wednesday afternoon and evening as the
surface low tracks across central Michigan with the anticipated line
of strong to severe thunderstorms on the prefrontal trough if
instability remains available into the evening. All hazards will be
in play with current timing of greatest threat window based on CAM
solutions some time between 23Z and 04Z. Damaging wind impacts, QLCS
tornadoes, and heavy rainfall will be the greatest threats with
Wednesday evening activity.

Thunderstorm potential continues on Thursday as ascent remains
present with the arrival of the main longer wave trough. Then a
brief break in precipitation chances during the day Friday before
ridge riding MCS potential comes into play Friday night in Saturday,
though trends have been more to the north with latest guidance.
Strong ridge of high pressure then builds into region resulting in
hot and very muggy conditions with high pushing above 90 degrees and
above for the weekend.

MARINE...

A low pressure system is tracking from northern Minnesota across the
northern Great Lakes this morning, pulling a warm front up through
the region. This will lead to southerly winds today generally
holding below 20 knots. The offshore flow should also minimize any
increased wave potential. A second low will pass over lower MI an d
Lake Huron on Wednesday bringing the potential for a round of strong
to severe thunderstorms across the region Wednesday afternoon into
the overnight. Active pattern could continue through the end of the
week with a cold front stalling across northern MI Thursday and
another low Friday night or Saturday.

HYDROLOGY...

Gulf moisture feed pushing PW values near daily records offers heavy
rain/flooding potential with storms Wednesday and Wednesday evening.
Soundings show warm cloud depths of 12-15kft throughout the day
increasing precip efficiency with any preceding showers/storms along
the front daytime Wednesday as well as convection with the low
itself late day. One additional point of concern that will need to
be watched in coming model cycles is some signal amongst model
solutions supporting training convection during the day along the
frontal boundary before the arrival of the low which could boost
overall QPF. Average rainfall totals over the course of Wednesday
will be 0.75-1.50 inches with locally higher totals possible.
Stronger storms and/or repeated rounds of thunderstorms will be
capable of a quick 1-2 inches in a 1-3 hour window. This brings with
it flooding concerns, especially if higher intensity rainfall
impacts urban areas.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
DISCUSSION...AA
MARINE.......DRK
HYDROLOGY....AA


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