377
FXUS63 KDTX 090859
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
359 AM EST Sat Nov 9 2024

.KEY MESSAGES...

- Dry conditions with temperatures slightly above early November
normals today.

- Rain arrives after 4 AM Sunday as a large low pressure system
moves across the Midwest with warming temperatures into the low 60s.

- A more seasonable airmass settles in for the first half of next
week as drier conditions return.

&&

.DISCUSSION...

Seasonably cool temperatures at daybreak rebound efficiently this
morning as surface flow veers southeasterly with time in response to
anticyclonically curved trajectories emanating from surface high
pressure. The surface ridge will continue to depart toward the east
across southern Ontario, eventually arriving at Lake Ontario and
Upstate New York by late afternoon. Thermal progs indicate warming
in the lower troposphere marked by H8 temps climbing from the low
single digits (Celsius) this morning to the upper single digits
later in the day. With the exception of the southern Lake Huron
shoreline, relatively clear skies are expected within the lowest 20
kft until the next low pressure system approaches.

The composite ridge axis responsible for ongoing subsidence will
flatten as it translates east across the state today which
eventually directs a latitudinally-oriented confluence zone atop the
Upper Midwest. This helps usher in a warmer (highs in the low to mid
60s) and more humid airmass (PWATs above 1 inch), preceding the
arrival of a deep occluded low. The cutoff cyclonic wave will drag
its occluded front and encompassing precipitation shield into
Southeast Michigan after 09Z. Most of the rain, including the
maximum areal coverage will occur from 12Z to 15Z resulting in
between a quarter inch to half an inch of rain. Areas closer to the
Ohio border coincide with PWATs close to 1.50 inches, and therefore
heavier rainfall rates. The system`s dry slot likely traverses
Southeast Michigan between 18Z and 21Z leading to a lighter and more
isolated showers before an accompanying cold front brings breezy and
potential for renewed showery conditions later in the day.

Brief warm advection/ridging occurs behind the low Monday, but will
quickly be overtaken by the next VortMax and clipper low working
across central Ontario Monday night. This forces another cold front
through the region, albeit with higher likelihood for rain-free
conditions. High pressure builds aggressive into the area behind the
front Tuesday, persisting into Wednesday until an energetic and
perturbed jet sends additional shortwave disturbances over north-
central CONUS the second half of next week. This ensures several
opportunities for additional rainfall Wednesday night and/or
Thursday, depending on the movement of the jet stream.

&&

.MARINE...

A high pressure system will quickly move over the Great Lakes
through the morning and afternoon hours before washing out across
New England this evening. This will support lighter winds while wind
direction veers from ENE to SE during the morning to afternoon
timeframe. A low pressure system then remains on track to move from
the central Plains into the northern Great Lakes by tomorrow
afternoon and evening. This will further back wind direction from
the SE to the SW through the day tomorrow while bringing widespread
rain showers.

Lingering showers will be possible Monday into early Tuesday
morning, favored over Lake Huron, as high pressure starts to fill
back in from the west. This approaching high pressure will
strengthen the pressure gradient over the lakes while bringing a
glancing push of cooler Canadian air. There will be a small window
for elevated wind speeds and gusts as the gradient tightens, which
brings the renewed chance to see Small Craft Advisories for portions
or all of the Saginaw Bay and Lake Huron shoreline. High pressure
then then moves over the region late Tuesday morning, relaxing winds
and ending all rain chances.

&&

.PREV DISCUSSION...
Issued at 1141 PM EST Fri Nov 8 2024

AVIATION...

The center of surface high pressure will drift across the Lake Huron
basin to the eastern Great Lakes early Saturday. A dry ambient air
mass and strong static stability between 2.5 and 10.0 kft agl will
maintain VFR conditions throughout the taf period. A light northerly
wind at taf issuance time will steadily veer to the northeast
tonight and eventually southeast by Saturday evening. Will be
watching for some patches of lower boundary layer cloud advecting
off of the Great Lakes in easterly flow trajectory, but very
difficult to pin down timing, coverage, and duration. Upper level
diffluence ahead of closed upper level low pressure will bring a
veil of lowering high cloud to the area late Saturday. Widespread
rain is expected to hold off until after 06Z 11/10.

DTW THRESHOLD PROBABILITIES...

*  None


&&

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

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

$$

DISCUSSION...KGK
MARINE.......AM
AVIATION.....CB


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