921
FXUS63 KDTX 200401
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1201 AM EDT Sun Apr 20 2025

.KEY MESSAGES...

- Cooler and drier through the weekend.

- Shower and thunderstorm chances Sunday night and Monday.

- Windy conditions Monday afternoon and evening with gusts in excess
 of 35 mph possible.

&&

.AVIATION...

Surface ridge makes inroads across Lower Michigan tonight ensuring
dry conditions for another 18 hours. Winds veer from northerly to
easterly by sunrise with decreasing speeds. Stable lower column
environment should result in cloud-free conditions below 5 kft AGL.
VFR high cirrus will thin-out as the jet axis gets reoriented due to
quick amplification of the upper-level longwave ridge over the Great
Lakes. High pressure gets forced out with time, into Canada (ON/QB),
as a fast moving surface low lifts across the eastern Plains and
into the Midwest Sunday evening. VFR conditions with showers develop
toward the end of the TAF period with the system`s warm front
lifting in, but moisture quality is poor, thus not worth a rain
mention just yet.

.DTW THRESHOLD PROBABILITIES...

* Low for ceiling at or below 5000 feet Sunday evening.

&&

.PREV DISCUSSION...
Issued at 337 PM EDT Sat Apr 19 2025

DISCUSSION...

Cold air advection following the front earlier today has brought
temperatures down compared to yesterday with mid 60s to low/mid 50s
from south to north respectively here at press time. With the front
draped across western Lake Erie there will be a low chance for rain
showers through the remainder of the afternoon near the southern
border.

High pressure becomes further established this evening into tomorrow
resulting in dry conditions. Temperatures at 850 mb fall to around
0C across the northern half of the CWA overnight. Light northerly
winds and decreasing coverage of clouds will allow temperatures to
fall into the low 30s across the Thumb and Saginaw Valley and into
the low 40s across the Detroit Metro to southern border areas. Cool
east to northeast onshore flow will maintain the slightly below
average temperatures for tomorrow with most areas holding in the 50s
for the afternoon with the exception of the Thumb shorelines that can
expect high temperatures in the 40s.

Strengthening low pressure system organizes out of the southern
plains along an elongated frontal zone and lifts into the Midwest
tomorrow into Monday. Associated warm front reaches into Lower MI
late Sunday evening. There will be a low chance for some showers
along the frontal slope during the afternoon Sunday, but the likely
rainfall with a chance for thunderstorms is more likely Sunday night
into Monday morning as the occluded system lifts into the western
Great Lakes. Lack of surface instability will preclude severe mention
at this time. QPF looks on the lighter end to a quarter inch or
less. Quality of theta-e with a few hundred joules of MUCAPE will
support the thunder chances. Southeast Michigan would spend a brief
period of time in the systems warm sector if it makes it up here
Monday morning before they systems cold front swings through.
Increasing gradient flow and cold advection behind this front will
support windy conditions with gusts of 35 mph or greater possible
Monday afternoon and evening. High pressure fills in behind front
easing the gradient late Monday evening. Lack of strong cold
advection will bring near average to above average temperatures for
the early to late week period.

MARINE...

This morning`s cold front has since settled to the southeast of
local waters, leading to a general west-northwest flow pattern
across the central Great Lakes. The cooler airmass is notably drier
with precipitation holding to the southeast. Benign marine
conditions carry into Sunday with winds veering toward the east-
southeast as the high pressure center drifts overhead tonight. Next
chance for impactful weather arrives early Monday morning as low
pressure lifts through the upper Midwest toward Lake Superior. This
system will be responsible for elevated showers and thunderstorms
impacting the area early Monday morning, with potential for activity
to linger through mid-day. This system draws an occluding front
across the Great Lakes Monday afternoon, ultimately leading to
colder/well-mixed profiles in the evening that will bring gusty
winds to the lake surface. With water temperatures being a couple of
degrees warmer over Saginaw Bay, and winds being southwest in
direction, locally enhanced gusts may approach gale force Monday
evening. At the very least, Small Craft Advisories will be needed on
Monday for the nearshore zones.

&&

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

$$

AVIATION.....KGK
DISCUSSION...AA
MARINE.......MV


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