404
FXUS63 KDTX 241058
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
658 AM EDT Sat May 24 2025

.KEY MESSAGES...

- A few sprinkles with perhaps a couple isolated showers over the
  Thumb in store for today and Sunday with gradual warming, into the
  low 60s.

- Warming and drying trend continues into Memorial Day and early next
  week.

- Chance for more widespread rain arrives Tuesday PM into Wednesday.

&&

.AVIATION...

High pressure extending from central Canada into the Midwest
maintains a light NW wind and a cool air mass across Lower Mi today
and tonight. The cool air and daytime instability support a lower
cloud component again today but which is more firmly in low end VFR
outside of a few MVFR pockets this morning. High pressure drifting
closer to Lower Mi maintains light NW wind but aids in a cloud
decrease tonight into Sunday morning.

For DTW/D21 Convection... No thunderstorms today or tonight.

THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet this morning. High this
  afternoon. Low tonight.

&&

.PREV DISCUSSION...
Issued at 350 AM EDT Sat May 24 2025

DISCUSSION...

Effectively dissolved nocturnal cloud field yields a clear and
chilly sunrise for most this morning as the large-scale pattern
begins to reorient, albeit rather slowly. Lower Michigan will reside
along the interface between the subtropical jet and an amorphous
upper low encompassing portions of The Northeast, the Great Lakes,
and Ontario/Quebec. Expectation is for a retreating CVA response
(toward the north) during the late morning and mid-day hours as mid-
level geopotential heights build in from the south. While this
ensures a period of active mid-level subsidence, a shallow cloud-
bearing mixed-layer should offer sufficient lapse rates to generate
pockets of weak ascent/sprinkles. Forecast soundings reveal a dry
boundary-layer which could result in more virga than light rainwater
as hydrometeors descend toward the surface. Given how Friday
unfolded, the latest consensus CAM simulated 1 km dBZ field, and
evidence of non-zero QPF chances per HREF/DESI, did make PoP
revisions. Opted to raise PoPs to Slight Chance northeast of a line
from Caro to Port Huron where the vorticity ribbon overlaps longest,
and added sprinkle mentions southwest of the line, down to the I-75
corridor. Decent thermal gradient arises from southwest to northeast
this afternoon with 850 mb temperatures of 3-4C near the Ohio Border
and only 1-2C over The Thumb. This translates to highs just shy of
60F for The Thumb, and low to mid 60s elsewhere.

A secondary mid-level circulation evident in GOES vapor imagery over
western Ontario will link up with the southern stream jet and eject
southeast across Lower Michigan on Sunday. The VortMax quickly gets
sheared apart by the more dynamic jet flow which lends low
confidence in a true convective response, but should still note
ensemble agreement in +100 J/kg of SBCAPE (20-40 percent chance).
With equilibrium levels rather shallow, and rumble of thunder will
be isolated and infrequent. Went with another combination of Slight
Chance PoPs for the northeast portion of the forecast area and
sprinkle mentions further south. Incremental warming Sunday with
highs in the low to mid 60s across Southeast Michigan.

Ridge amplification extends into Lower Michigan Memorial Day
ensuring drier conditions, but 850 mb temperatures will still run a
bit cool at 5-7C (25th percentile is 6C). This corresponds with
highs approaching 70F, which is still several degrees below
climatological normals. Diffuse surface high pressure field extends
across the region Monday into Tuesday morning keep winds light with
an easterly component beneath diurnal cumulus clouds. A shortwave
trough over the Desert Southwest phases with an orphaned upper low
over The Dakotas Tuesday. This affords some potential for higher
quality moisture advection up through the Ohio Valley and into
southern Lower mid-week. Still a lot of moving pieces that need to
properly fall into place to equate to higher confidence in showers
for the local area. NBM Chance PoPs still seem appropriate at this
juncture. Temperatures return to seasonal normals next week with
cloudier periods leading to slightly cooler days Tuesday and
Wednesday but still near the 70F mark.

MARINE...

A low pressure system will exit north of Lake Ontario today which
will continue to reinforce northwest flow across the Great Lakes.
High pressure then begins to fill in across the Great Lakes this
weekend, centering over the region on Monday. This will support
light winds and some extended periods of dry weather. Light
northwest flow holds through early Monday, with veering to the
northeast as the high pressure system arrives.

&&

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

$$

AVIATION.....BT
DISCUSSION...KGK
MARINE.......AM


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