018
FXUS63 KDTX 091800
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
200 PM EDT Sun Jun 9 2024

.KEY MESSAGES...

- Afternoon showers will mainly develop over The Thumb region with
  lighter rates further south and east.

- Gusts peak near 30 mph today before subsiding overnight.

- High pressure brings dry conditions for the first half of the
  week.

- Cool on Monday followed by a warming trend back into the mid to
  upper 80s by latter half of the week.

&&

.AVIATION...

Diurnal cloud response underway as a deep mixed-layer develops this
afternoon. Not only does this support the expansion of high-based
VFR cumulus, but 30+ knot flow within the low-levels will continue
to mix down producing similar peak wind gusts. Winds generally hold
from 260-280 degrees until a weak frontal boundary crosses from
northwest to southeast over the next 3-4 hours. Some showers have
accompanied the FROPA, but most of this activity should remain over
The Thumb and points east of the terminals. Winds behind the front
veer toward 310 degrees while maintaining some gustiness until this
evening, but speeds should decline enough to hold below crosswind
thresholds (for DTW). Clouds linger tonight as low-level cold
advection helps to cool and moisten the column leading to lowering
of cloud bases with time. A period of high-end MVFR ceilings remains
possible after midnight. Low clouds mix out late Monday morning with
weak energy aloft touching off a period of VFR mid and high clouds
during the midday timeframe.

For DTW/D21 Convection...Thunderstorms are not expected through the
TAF period.

 DTW THRESHOLD PROBABILITIES...

* Low in ceilings at or below 5000 feet this afternoon.

* Low in exceeding crosswind threshold.

&&

.PREV DISCUSSION...
Issued at 350 AM EDT Sun Jun 9 2024

DISCUSSION...

Subsidence inversion has developed in the wake of the cutoff
mid/upper level low that will continue to drift east into Quebec
today. Post rainfall moisture boost is trapped under this inversion
supporting the development of low clouds. Expect lower clouds to
gradually scatter out post sunrise. The central Great Lakes will be
under northwest mid/upper level flow on the western side of the
Canadian trough, which will usher in another disturbance this
afternoon. Overall moisture will be lacking a bit, but just enough
daytime instability should be able to support a few stray showers.
Greatest PoPs (~20)% will be favored across the Thumb. The 850-925mb
layer flow will ramp up to 30 knots or greater by this afternoon.
Mixing depths are forecast to climb to nearly 10 kft for some
locations with high low level lapse rates to 10 C/km. This should
easily mix down wind gusts to 30 mph or greater with perhaps a few
isolated gusts approaching 40 mph. The peak of these westerly wind
gusts will fall between 11 am and 6 pm. Wind speeds will begin to
decline this evening in the wake of a cold front while turning out
of the northwest. This will usher in a cooler airmass tonight and
bring overnight lows ranging from the mid/upper 40s to low 50s.
Long northwest fetch across Lake Huron will maintain at least low
precipitation chances in the form of sprinkles/light rain for the
Lake Huron shorelines with continued mid-level shortwave support
dropping out of Ontario early tonight.

High amplitude ridging builds across the plains and Midwest with a
surface high pressure spreading across the Great Lakes early to mid-
week. This will bring dry weather for the bulk of this period. It
will be a cool start to the work week though as temperatures of 4-6C
at 850 mb settle across the region for Monday afternoon. The result
will be a day of below normal temperatures with daytime highs down
in the low to upper 60s for the bulk of southeast Michigan. We start
to get some return flow on Tuesday as the ridge axis moves over the
central Lakes. This will increase temperatures on Tuesday back into
the 70s for daytime highs. This also marks the start of a warming
trend that will carry into the late week as the ridge tracks
eastward and progressive zonal flow ushers in much warmer air into
the region from the west. Temperatures at 850 mb into the mid teens
C will support highs approaching 90 degrees across metro Detroit by
Thursday.

Moisture transport increases Wednesday into late week bringing
higher dewpoints more solidly into the 50s by Thursday. This sets the
stage for the next chance for precipitation during the Thursday-
Friday period as the west to East mid/upper level jet helps push a
cold front into the Great Lakes. Timing uncertainty exists as
activity will largely depend on how convection evolves upstream in
the plains.

MARINE...

Friday`s low finishes vacating the area early this morning setting
up northwesterly flow in its wake. Lingering, deepening low pressure
over Quebec tightens the local gradient resulting in an uptick of
winds early this afternoon into tonight with gusts generally topping
out around 25kts. Potential exceptions remain northern Lake Huron
(due to favorable fetch) and Saginaw Bay (due to warmer waters)
where peak gusts could reach around 30kts this afternoon-evening.
Small craft advisories are in effect for the Saginaw Bay and
southern Great Lakes due to these wind gusts with the remainder of
Thumb under advisories tonight into Monday as northerly winds push
higher wave action into the nearshore waters. High pressure then
builds over the Great Lakes Monday relaxing winds and supporting dry
conditions for the first half of next work week.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT this evening for LHZ422.

     Small Craft Advisory until 4 PM EDT Monday for LHZ421.

     Small Craft Advisory from 2 AM to 10 PM EDT Monday for LHZ441>443.

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.

&&

$$

AVIATION.....KGK
DISCUSSION...AA
MARINE.......KDK


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