292
FXUS63 KDTX 081641
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1141 AM EST Fri Nov 8 2024

.KEY MESSAGES...

- Dry and breezy today with temperatures at or slightly above early
November normals through Saturday.

- Rain arrives early Sunday morning as a large low pressure system
moves across the Midwest with warming temperatures.

- A more seasonable airmass settles in for the first half of next
week.

&&

.AVIATION...

A shallow moist layer near the top of the inversion will support a
few MVFR based diurnal clouds through the early afternoon. Expect
there to be some erosion of these clouds during the course of the
afternoon with subtle boundary layer growth. 20 knot winds within
the shallow daytime mixed layer will sustain some level of gustiness
to the winds this afternoon. The onset of nocturnal cooling around
22-23Z will lead to a notable drop in the winds. High pressure will
move east across Lower Mi tonight into Saturday morning. This will
result in a veering of the low level wind fields from WNW this
afternoon to ENE by Saturday morning. Additional moisture flux off
the lakes may support some additional MVFR clouds late tonight into
the first half of Saturday.

DTW THRESHOLD PROBABILITIES...

*  None

&&

.PREV DISCUSSION...
Issued at 357 AM EST Fri Nov 8 2024

DISCUSSION...

Mainly clear skies with temperatures starting out in the 40s
precedes synoptic-scale eastern Plains ridging that will deflect a
deepening longwave trough and its associated jet max toward the
east. The encroaching ridge reinforces static stability through much
of the column as evidence by 08.00Z KDTX RAOB and upstream
soundings. Forecast soundings do hint at a brief period of glancing
mid- and upper-level cyclonically induced ascent, but antecedent
dryness limits the overall affect to some midday cirrus generation.
Within the boundary layer environment, expect a sparse diurnal
cumulus response in addition to mechanical mixing. Enhanced westerly
H9-H8 flow trends lower with time today as the mixed-layer deepens.
Should see an early afternoon peak with gusts in the mid 20 mph
range (perhaps upper 20s further north), and revised winds upward,
appropriately. Temperature-wise, the warmest potential temperatures
aloft lie near the H7 level (INVOF subsidence induced warming),
therefore boundary-layer mixing depths peak near the H8 level where
temperatures are in the 6-8C range. This translates to highs today
in the mid-upper 50s, and near 60F from Metro Detroit toward the
Ohio border. Clear skies return overnight as the 1030 mb surface
high translates over the Upper Midwest and Upper Peninsula which
flips gradient flow easterly into Saturday. Veering winds will
promote cold advection with overnight lows dropping below freezing
along/north of I-69, except along the lakeshore where potential lake-
augment low clouds form.

Temperatures rebound efficiently off morning lows Saturday as winds
continue to veer, becoming southeasterly as return flow ensues
behind the departing surface ridge. Colder low-level environment
leads to lower dewpoint depressions and increasing cloud fraction
Saturday while dry weather persists for one more day. A large
occluded low emerging from rapid lee-cyclogenesis lifts northeast
across The Plains and into the Upper Midwest late Saturday night and
into Sunday. Expected a well-defined comma head precipitation shield
to overspread Southeast Michigan early Sunday morning bringing
steady rainfall through midday, before a transition to lighter
showers through the rest of the daylight hours. Breezy conditions
will accompany the rainfall with stronger winds later in the day as
the system`s cold front works through.

More seasonable conditions expected Monday and Tuesday in the wake
of the low with ample cloud cover and occasional light showers. A
clipper system works across central Ontario Monday night driving a
secondary cold front through Lower Michigan, albeit with less
precipitation. High pressure builds rapidly into the region mid-week
flipping to warm advection and southeast flow while unsettled
conditions trail. An energetic and perturbed jet stream sends
additional shortwaves into the region for the second half of next
week.

MARINE...

Tightened gradient over the central Great Lakes holds through the
morning before departing James Bay low pressure allows upper Midwest
high pressure to build into the Great Lakes late day. During this
timeframe, gusts of 20-25kts remain possible across the region with
25-30kts over the northern half of Lake Huron. A cold front glances
the region this afternoon shifting winds to the northwest though
still largely maintaining their strengths. This shift likely results
in higher wave action along the Thumb nearshore waters requiring
another Small Craft Advisory late today into tonight. High pressure
then begins to become established this evening resulting in a steady
weakening trend in winds. Said high drifts overhead Saturday
offering a relatively brief period of light winds. Unsettled weather
returns by Sunday as low pressure lifts out of the Plains and
through the Great Lakes.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 AM EST Saturday for LHZ421-441>443.

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

$$

AVIATION.....SC
DISCUSSION...KGK
MARINE.......KDK


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