991
FXUS63 KDTX 222300
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
700 PM EDT Thu May 22 2025

.KEY MESSAGES...

- Scattered rain showers and drizzle taper off tonight.

- Chances for isolated to scattered afternoon showers this weekend
though most areas likely stay dry.

- Daytime temps rebound slightly into the 60s this weekend. These
seasonably cool temperatures likely persist through the first half
of next week.

&&

.AVIATION...

Lingering pockets of MVFR cloud and accompanying brief showers/
drizzle will exit late this evening, leaving a higher based VFR
cloud for the overnight period. Potential exists for a brief window
of clearing ahead of an approaching mid level low. This system will
bring renewed expansion of lower cloud mid-late morning Friday.
Ceiling heights will drop back into MVFR during this time. High
coverage of MVFR to low VFR stratus/stratocu will persist through
the latter half of the day. Prevailing wind from the northwest
through the period, turning intermittently gusty Friday.

For DTW/D21 Convection... No thunderstorms expected through the
period.

THRESHOLD PROBABILITIES...

* High for ceilings at or below 5000 through this evening. Medium
  overnight, then high again Friday.

&&

.PREV DISCUSSION...
Issued at 257 PM EDT Thu May 22 2025

DISCUSSION...

A mixture of scattered light showers, drizzle, and mist continues
into the evening as stacked low pressure remains in place over
southern Ontario. Drier air currently over the northwestern Great
Lakes, seen on water vapor imagery as well as evident on visible
satellite, is wrapped into southeastern Michigan late this
evening/tonight resulting in steady top-down column desaturation.
Loss of moisture should allow for a fairly rapid tapering off of
lingering showers across the region. Some clearing skies possible
late tonight mainly over the southern CWA as the main surge of drier
air pushes into northern IN/OH; however with continuing cool
cyclonic flow below the upper trough still in place overhead, low
moisture is not expected to be fully scoured out resulting
persistent cloud cover through Friday. Another mid-level wave drops
out of the southern James Bay over Lake Huron daytime Friday
steepening lapse rates as the mid-levels cool offering isolated to
scattered showers the latter half of the day- best chances focused
towards the Thumb.

Shortwaves finally push east of the region Friday night-Saturday as
they merge with the remnants of the Nor`easter, though low amplitude
upper troughing holds across the Great Lakes. Another shot at
afternoon pop-up isolated/widely scattered showers comes Saturday as
a lobe of vorticity embedded with mid-upper flow provides renewed
steepening of lapse rates below weak upper divergence. Similar story
for Sunday as yet another vort max tracks over the central Great
Lakes. Some temperature recovery (ie back into the 60s) can be
expected this weekend as flattening upper flow supports modest
height rises and more breaks in cloud cover weakening lingering
thermal troughing and allowing 850mb temps to climb from -1-0C Sat
AM to 2-3C by Sunday PM. Any further moderation is stalled this
coming work week as broad upper troughing redevelops over the
eastern CONUS maintaining seasonably cool conditions.

MARINE...

A low pressure system will continue to meander across Lake Erie and
Lake Ontario through Friday, before phasing with a second low
pressure system over New England. This will maintain northwest flow
to end the week. The slight backing of wind direction through this
evening in conjunction with a weakening pressure gradient will relax
wave heights across the Lake Huron shoreline by late tonight. This
will allow ongoing Small Craft Advisories to end late tonight.
Otherwise, on and off rain showers will continue through the week.

&&

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

Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&

$$

AVIATION.....MR
DISCUSSION...KDK
MARINE.......AM


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