819
FXUS63 KDTX 110654
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
254 AM EDT Sat May 11 2024

.KEY MESSAGES...

- Cooler temperatures (50s to low 60s) continue today before
returning to at or above normal Sunday into Monday.

- Compact low pressure system tracking across the central Great
Lakes brings showers through this morning before a brief midday lull
as additional showers and thunderstorms then redevelop this
afternoon/evening. Severe weather is not expected.

- 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.

&&

.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.

&&

.PREV DISCUSSION...
Issued at 1152 PM EDT Fri May 10 2024

AVIATION...

A compact and strong low pressure system tracking through the
western Great Lakes arrives late tonight into Saturday morning.
Widespread line of MVFR showers and a slight chance of an embedded
in the 8-13z window. The chance for thunderstorms is too low and
short lived to put in tafs at this time. Borderline MVFR/VFR CIGS
during the day hold through Saturday evening. Westerly winds
increasing behind the low, with gusts of 25+ knots likely by early
afternoon. Additional scattered showers develop during the day with
the steepening low level lapse rates and cold advection.

For DTW/D21 Convection... A stray thunderstorm is possible within
the band of showers Saturday morning due to the steep mid level
lapse rates. Westerly winds increasing during the day, with gusts
reaching at least 25 knots.

DTW THRESHOLD PROBABILITIES...

* Very low for an isolated thunderstorm Saturday morning.

* High for cigs aob 5000 ft after 9z Saturday.

* Medium confidence in reaching westerly crosswind threshold Saturday
  afternoon.


&&

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

Lake St Clair...Small Craft Advisory from noon today to 8 PM EDT this evening for
     LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from noon today to 8 PM EDT this evening for
     LEZ444.

&&

$$

DISCUSSION...KDK
MARINE.......KGK/KDK
AVIATION.....SF


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