Marine Thunderstorm Winds in Lake St. Clair, May 19, 2026

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
232 PM EDT Tue May 19 2026

.KEY MESSAGES...

-  Severe thunderstorm watch is in effect for the eastern two thirds
of the CWA until 7 PM

- Dry and cool Wednesday through Friday morning.

- Rain returns by Friday evening and continues into Saturday.

&&

.DISCUSSION...

Pressure fields clearly show the prefrontal trough tracking through
western sections of the CWA. This trough will serve as the focus for
continued convection. Southwest gradient winds have been gusting 30
to 40 mph this afternoon, indicative of some decent wind fields.
With temperatures reaching the mid-80s and dew points in the mid-to-
upper 60s, MLCAPEs have reached 1500+ J/kg south of M-59. Per latest
SPC mesoscale analysis and DTW ACARS data, the CIN/cap has eroded
completely. Thus, further shower and thunderstorm development is
expected through the rest of the afternoon. A severe thunderstorm
watch is in effect for the eastern two-thirds of the CWA until 7 PM,
but there is a good chance it may be canceled earlier.

Localized/scattered damaging wind gusts should be the dominant
hazard, given the mainly unidirectional low-level flow and good
downdraft capes. However, because of the earlier start to activity
and weak convergence along the prefrontal trough, it may be tough to
sustain updrafts to support organized severe storms (barring any
interactions with outflow boundaries).

The actual cold front still needs to move through during the evening
hours, and additional storms will be possible with any leftover
instability. However, expect this prefrontal activity to deplete
much of the fuel for the main front.

Upper-level confluent flow and sprawling high pressure (1032 MB)
will be in place tomorrow through Friday morning over the Great
Lakes region, supporting dry and cool weather.

Rain showers will return by Friday evening, however. Longwave
troughing over the Rockies will capture and send a subtropical
shortwave and moisture-laden warm front into southern Lower Michigan
by Friday night. 850 MB dew points are progged to reach into the
lower teens (Celsius) on Saturday. EPS probabilities for 24-hour
rainfall exceeding half an inch are in the 60-70 percent range for
the bulk of southeast Michigan.

&&

.MARINE...

Small Craft Advisories remain in place into this evening as
southwest winds gust around 25 knots along the land/marine
interface. The development of strong to severe thunderstorms is
increasingly likely this afternoon into the evening, favored across
southern Lake Huron and locations south. A Severe Thunderstorm Watch
is now in effect until 7PM EDT. Wind gusts aoa 45 knots will be the
primary hazard for severe weather development. Passage of the cold
front will end the severe weather threat, veering winds from the
southwest to northwest through the evening. High pressure builds
behind the front, bringing lighter winds through the midweek period.

&&

.PREV DISCUSSION...
Issued at 204 PM EDT Tue May 19 2026

AVIATION...

Another hot and humid day (by mid-May standards) lends potential for
diurnal convection this afternoon and early evening. To the west of
the terminals, initial updrafts are testing what little remains of
the capping inversion layer, characterized by shallow updrafts and
limited glaciation/lightning. Meanwhile, sufficient daytime
insolation should lead to surface-based instability within the next
couple of hours marking an expansion in convective coverage across
some of the terminals. Confidence is highest from PTK south, but
uncertainty in overall coverage/intensity of thunderstorms remains.
FNT will be right on the edge of the pre-frontal troughing so opted
for a VCTS mention as opposed to a TEMPO for thunder the rest of the
PM hours. Visibilities will drop to IFR in the heaviest downpours.
Non-convective gusts have stayed elevated given the ambient wind
fields, but expect enhancements within water-loaded downdrafts.
Nocturnal stabilization emerges overnight as gusts drop-off, and
gradient winds gradually veer toward the north throughout the
overnight hours. Post-frontal northerly flow draws a plume of low-
level moisture through Southeast Michigan late tonight into
Wednesday morning favoring MVFR ceilings.

D21/DTW Convection...Window for scattered convection is focused
between 20Z and 23Z this afternoon/evening, although initial storms
could drift eastward a bit sooner. Storm motion will be southwest to
northeast around 40 kt while the corridors of storms migrate west to
east. IFR visibility reductions possible in heaviest downpours.

DTW THRESHOLD PROBABILITIES...

* Medium for thunderstorms 20-23Z today.

* Medium for ceilings at or below 5000 ft through this evening, then
  high early Wednesday.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ421-422-
     441>443.

     Dense Fog Advisory until 4 PM EDT this afternoon for LHZ361>363-
     462>464.

Lake St Clair...Small Craft Advisory until 10 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 10 PM EDT this evening for LEZ444.

&&

DISCUSSION...SF
MARINE.......SF
AVIATION.....KGK

You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.

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