Expert Forecast Opinion

041
FXUS63 KDTX 211004
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
604 AM EDT Mon Apr 21 2025

.KEY MESSAGES...

- Potential for showers to develop through the early afternoon, with
a slight chance of thunderstorms during this time.

- Turning windy this afternoon and evening with southwest gusts
of 35 to 45 mph.

- Warmer conditions through the midweek period.

&&

.AVIATION...

Surface warm front lifts partially into SE MI this morning as parent
low pressure reaches northern Lake Michigan maintaining scattered
shower chances into mid-morning (~14-16Z). Can`t rule out some
embedded thunder though overall potential and coverage are lower
relative to earlier this morning so have let the TEMPO mention drop
out from running forecast. Ceilings lower towards low VFR-high MVFR
early this morning with these showers. Some scattering looks
probable over the southern terminals behind this front based on
upstream satellite obs over IL/IN however this will be short lived
as the attendant cold front quickly sweeps through late morning-
early afternoon. Front brings renewed low cloud with additional
periods of MVFR cigs as well as much stronger southwest winds as
gusts reach around 35kts across the region. Winds steadily weaken
overnight with cloud coverage dissipating towards clear or mostly
clear.

For DTW...An isolated thunderstorm chance lingers for the first few
hours of the new forecast period however overall potential and
coverage expected to be lower than earlier this morning. Shower
chances end with the arrival the cold front late morning ushering in
strong southwest (210-240deg) winds for afternoon-evening as gusts
reach near 35kts.

.DTW THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 feet by mid-morning into this
evening (few hour period late morning for clouds to briefly
scatter between fronts). Low tonight.

* Low for thunderstorms between 12Z to 16Z this morning.

&&

.PREV DISCUSSION...
Issued at 357 AM EDT Mon Apr 21 2025

DISCUSSION...

1003 mb surface low positioned over southern WI early this morning
will track to near eastern Lake Superior by evening. Narrow axis of
deeper moisture anchored along the inbound associated warm frontal
boundary on pace to sweep across southeast Michigan through the
morning period. Ascent remains sufficient to support pockets of
shower development, with a few rumbles of thunder plausible given
presence of weak elevated instability. Early day warm frontal timing
affords a short window /15z-18z/ of low level warm/moist advection,
before the trailing cold/occluding front sweeps through mid-late
afternoon. This will bring temperatures into the 60s. Meaningful
surface destabilization will be lacking to support a greater
secondary convective response, but isolated sub-severe convection
remains possible during this time. Notable increase in gust
magnitude occurs within the immediate wake of this fropa, backed by
a firm southwest gradient in excess of 20 knots and solid a 30-35
knots comfortably within the the mixed layer. Greatest mixing
potential occurs as a few breaks emerge in the cloud initially
within the post-frontal environment, but then becomes increasingly
compromised as lower cloud increases coverage diurnally. This
appears to place a ceiling on prospective gust potential overall to
around 45 mph. Gusts of 35 to 45 mph will remain common through the
evening hours under sustained cold air advection, despite persist
low stratus.

Lower amplitude westerly flow to govern conditions throughout the
mid week period. General mid level subsidence atop pervasive surface
ridging ensures benign conditions Tuesday, as the resident thermal
profile favors temperatures edged on the warmer side of average.
Weak warm frontal boundary lifts into the region Tue night,
responding to some increase in southerly flow upstream as weak
shortwave energy traverses the central conus. A modest increase in
both moisture quality and ascent in the vicinity of this boundary
will provide a chance for shower development overnight and possibly
into early Wednesday. The onshore flow north of the boundary will
maintain notably cooler conditions across the eastern thumb, while
southern areas push toward 70 degrees Wednesday. Moderating thermal
profile takes an additional upward step Thursday as upper heights
build. Prevailing low level southeast flow may offer some
Resistance, but projected highs now targeting the low to mid 70s for
all locations but the eastern thumb.

MARINE...

Low pressure currently over Wisconsin will lift northeast toward the
Straits throughout the day. Several rounds of showers and a few
embedded thunderstorms will persist through the morning hours prior
to the passage of an occluded front this afternoon. Strong warm
advection with this system keeps majority of the waterways stable,
although the land-lake interface presents typical concerns for land-
based gusts to reach the shoreline. In this case, a short-fused Gale
Warning may be necessary if observations warrant. Potential for a
period of marginal gales will exist across Saginaw Bay late this
afternoon through the evening hours. A Gale Warning now exists for
this corridor, while High-end Small Craft Advisories continue
highlight the short duration with sporadic gusts to gales elsewhere.
A more favorable setup for gales exists downwind of the Straits into
northern Lake Huron early Tuesday morning where colder air
temperatures and northwest flow funnel along the fetch. High
pressure builds in on Tuesday to support a more benign mid-week
pattern.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Warning from 8 PM this evening to 10 AM EDT Tuesday for LHZ361-
362.

Small Craft Advisory from 8 AM this morning to 2 PM EDT this
afternoon for LHZ421-422.

Small Craft Advisory from 10 PM this evening to 10 AM EDT Tuesday
for LHZ421-422.

Gale Warning from 2 PM this afternoon to 10 PM EDT this evening for
LHZ421-422.

Small Craft Advisory until 10 AM EDT Tuesday for LHZ441>443.

Lake St Clair...Small Craft Advisory from 10 AM this morning to 4 AM EDT Tuesday
for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 10 AM this morning to 4 AM EDT Tuesday
for LEZ444.

&&

$$

AVIATION.....KDK
DISCUSSION...MR
MARINE.......MV/MR

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