128
FXUS63 KDTX 111726
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
126 PM EDT Sat May 11 2024

.KEY MESSAGES...

- Widely scattered to numerous showers are expected through the
  afternoon and early evening hours, with best coverage expected
  across the Thumb.

- Another chance of showers and thunderstorms comes Monday as a cold
front drops through the region. This front looks to stall overhead
leading to persistent rain chances into early Tuesday.

&&

.AVIATION...

Widely scattered to numerous rain showers will continue through the
afternoon and early evening hours in response to the departing low
pressure system presently located over the Thumb. A rumble of
thunder is possible but coverage and duration remains too limited
for inclusion in the forecast. Cloud ceilings will attempt to lift
towards low-end vfr through the afternoon, however periods of mvfr
cigs are favored with the rain chances.

The cloud shield will gradually shift northeast tonight as low
pressure continues to travel east. This persistent cloud shield will
linger through the late evening to early morning hours over the
Thumb, and it will be a close call if the western edge of the shield
holds on across the terminals beyond Midnight. Most model guidance
supports the cloud coverage shifting just northeast of all terminals,
which is represented on the outgoing TAFS. Otherwise, breezy
westerly flow with gusts around 25 knots are expected during daylight
hours.

For DTW/D21 Convection...  Another round of showers are expected
with peak heating this afternoon into early evening. Thunderstorm
chances remain very limited.

DTW THRESHOLD PROBABILITIES...

* Very low for an isolated thunderstorm this afternoon into the early
  evening.

* High for ceiling 5000 ft or less today and tonight.

* Medium confidence in reaching westerly crosswind threshold this
  afternoon.

&&

.PREV DISCUSSION...
Issued at 254 AM EDT Sat May 11 2024

DISCUSSION...

Compact shortwave is digging into southern MI early this morning
with associated shower activity on the CWA`s doorstep at press time.
Fairly organized/coherent band of showers works across SE MI through
the first half of the morning before fully shifting east after ~14Z
with a narrow mid-level dry slot following as the low undergoes
occlusion. Still can`t rule out a rumble of thunder or two within
these showers given the strength of the parent vort max and weak
(<500 J/kg) of elevated instability- some lightning noted overnight
as it crossed Lake Michigan/west-central MI. Lull in precip is
shortlived as the now vertically stacked low wobbles toward the
Ontario peninsula. Both high-res and coarser model solutions have
trended more north and east with the low center compared to
yesterday where they advertised it sliding directly overhead. As a
result, while timing is still extremely favorable tap into peak
diurnal heating, greatest upper support will reside over the Thumb
down to roughly the M-59 corridor. These areas have the best
potential to see scattered, to perhaps briefly numerous, shower
development through the afternoon-evening. Conversely, areas to the
south likely will see coverage more limited to widely scattered to
isolated. A thunderstorm or two also possible among latter day
activity has daytime heating supports SBCAPE between 400-600 J/kg.

Troughing vacates early Sunday as low amplitude ridging takes its
place over the central Great Lakes. West-southwest return flow
beneath this ridge leads to robust WAA in southern lower MI as 850mb
temps climb from ~1-2C Sunday morning to ~12C Sunday evening. While
ridging influence will promote a generally drier day, worth noting
there is some signal amongst the high-res guidance for an area light
showers work into SE MI on the nose of the aforementioned warmer,
richer theta-e airmass as a subtle PV anomaly rides over the ridge.
Given the lower amplitude nature of the ridge, this feature is
plausible so have added slight chance PoPs (15-20%) late Sunday
morning/afternoon focused over the Tri-Cities/Thumb into the
northern Metro Detroit area. Otherwise above normal temps make their
return with highs Sunday in the upper 60s to around 70 further
increasing to low to mid 70s Monday.

A northern stream trough sags into the Great Lakes Monday allowing
an attendant surface cold front to likewise drop into the
western/central Great Lakes. This front continues to look to stall
over the area by midday Monday becoming the focal point for periods
of showers and thunderstorms throughout much of Monday. Southern
stream partially phases resulting in low pressure ejecting out of
the Plains toward the Ohio Valley Monday night-Tuesday. This has the
potential bring a renewed surge of moisture/lift to southern SE MI
Tuesday to support increasing coverage of showers daytime Tuesday...
if the track is far enough north. Mid-range solutions are split on
this more northerly track or a more southerly track closer to the
Tennessee valley keeping the bulk of activity south of the state
border. Regardless of which camp pans out, this low fully dislodges
the stalled front allowing high pressure and drier, more seasonably
average temperatures to return for the midweek period.

MARINE...

Southerly gradient winds trend higher today as a low pressure system
drops through northern Lower Michigan. An attendant cold front gets
pushed across Lake Huron helping afternoon gusts to reach Small
Craft Advisory criteria (25+ knots) over the Saginaw Bay as well as
Lakes St Clair and MI waters of Erie given the warmer water temps in
these areas. Some thunderstorms are also possible with this system,
mainly over southern Lake Huron during the afternoon which could
result in periods of locally stronger winds/waves. High pressure
briefly builds in Sunday morning providing favorable marine
conditions before a secondary low approaches later on Sunday. This
second system offers potential for enhanced southwest flow over
Saginaw Bay, and possibly Small Craft Advisory criteria gusts.
Showers and storms arrive late Sunday evening and overnight. A
stationary front then settles over the Great Lake early next week
offering additional opportunities for thunderstorms.

&&

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

Lake St Clair...Small Craft Advisory until 8 PM EDT this evening for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory until 8 PM EDT this evening for LEZ444.

&&

$$

AVIATION.....AM
DISCUSSION...KDK
MARINE.......KGK/KDK


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