407
FXUS63 KDTX 250838
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
338 AM EST Mon Nov 25 2024

.KEY MESSAGES...

- Low pressure tracking through the area will bring a high
likelihood of showers today and early tonight.

- The potential exists for an area of light snow to move across
the area Wednesday night and Thursday morning.

- Temperatures will dip well below average starting on Friday. These
colder conditions will persist through the remainder of the holiday
weekend.

- The colder conditions will bring a favorable environment for lake
effect snow showers to develop at times through the weekend.

&&

.DISCUSSION...

Early morning surface analysis shows low pressure tracking across
western Illinois, with a warm frontal zone stretching eastward into
northern IN/OH. Corridor of moist isentropic ascent emanating north
of these features maintained within the broader region of elevated
warm air advection, resulting in some pockets of shower activity
across lower Michigan. This underlying pattern remains unchanged
going forward today, as the inbound wave and warm frontal zone
contribute to an increasing field of upward vertical motion to offer
a scattered to numerous coverage of showers at times during the
daylight period. The advective process yields a modest recovery in
surface temperatures once low level flow veers toward a southerly
component this afternoon, netting a slight upward adjustment in
highs relative to recent days. Higher probability for rain showers
maintained into the evening window, with a focus provided by strong
height falls engaging ongoing cold air advection within the
immediate wake of the departing low.

Notably colder profile entrenched Tuesday within deep layer westerly
flow. Little recovery off morning lows expected as low level thermal
troughing takes residence - temperatures stalled mainly in the 30s.
Area to remain encased in low stratus as ongoing lake moisture flux
solidifies a standard moist plume downstream. Overall moisture depth
likely proves insufficient to support a greater downstream response
for lake effect in this environment. There is a signal for a
secondary period of synoptic scale moisture advection to rotate
across central lower mi late in the day. Potential would exist for
convective depth to grow sufficiently to generate a few pockets of
light snow showers or flurries across northern areas during this
time.

Behavior of a strong PV anomaly set to surge ashore across the west
coast over the next 24 hours will become the main player in pattern
evolution and corresponding sensible wx changes regionally and
locally as it ejects out of the plains within the Wednesday/Thursday
periods. A robust dynamic response expected along the immediate
northern flank of this system, as favorable upper jet forcing
intersects a moist and conditional unstable profile with some
evidence of frontal forcing. Key features still outside the window
for appropriate sampling from the upper air network, so unsurprising
that the collective of ensemble guidance maintain a varying solution
to the potential northward expanse of the governing forcing field
and resulting precipitation swath. In general, potential exists for
this axis to lift into a portion of lower Michigan during this time,
thus presenting a favorable environment for some accumulating snow
mainly Wednesday night into Thursday morning. It remains worth
noting that a subset of ensemble members, particularly within the
GEFS camp, maintain a more southerly track and support mainly dry
conditions. Outgoing forecast holds at a middle ground, highlighting
the chance for a mix of rain/melting snow starting late Wednesday
and trending to all snow with time, with greater potential with
southward extent.

Much below average temperatures will mark conditions for the
remainder of the holiday weekend. Highs at or below freezing during
this time, with lows in the teens in the coldest locations. Active
lake effect environment in cold west to northwest flow will bring
opportunities for local snow shower production within the background
of broader cyclonic flow. The high amplitude upper troughing in
residence will keep this pattern in place well into the first week
of December.

&&

.MARINE...

Low pressure strengthens as it lifts northeast into the Great Lakes
today, settling over Lake Huron late this evening. The low brings a
warm and stable airmass into the region, which will prevent strong
low level jet winds from mixing to the surface. The most notable
impact from this system will be continuous rain showers through the
day. Southerly winds veer to the west tonight as the low draws a
cold front across the Great Lakes, ushering in a colder airmass that
will transition precipitation type to a rain snow mix for Tuesday.
The cold advection will also deepen the boundary layer to support
gusty westerly flow. There has been a modest upward trend in gust
potential during this period as the stronger low level jet winds lag
behind and overlap with the cold advection. Still, peak winds at the
top of the boundary layer of only 35-40 knots will struggle to
generate widespread gales at the surface (would require nearly
perfect momentum transport). Additionally, west flow typically is
not a favorable flow regime for overachievement on the west side of
Lake Huron/Lake Erie. Thus have opted to hold off on a Gale Watch
for now. Unsettled weather continues into mid-week as another low
pressure system begins to develop upstream.

&&

.PREV DISCUSSION...
Issued at 1139 PM EST Sun Nov 24 2024

AVIATION...

Warm air advection has eroded the low level inversion which has
allowed the low stratus deck to clear across most of the area, with
the exception of Central Lower Mi. Low clouds will redevelop and
expand back across Se Mi during the morning Monday in advance of an
approaching warm front. This warm front is associated with low
pressure, which is forecast to track across the Saginaw Valley
Monday afternoon. Ample low level moisture associated with this
system will result in falling ceilings during the course of the
morning Monday, with prevailing IFR and some LIFR conditions in
light rain expected by Monday afternoon. As the low exits to the
northeast into Lake Huron Monday evening, much colder air will
advance into the area from the west. This will result in increasing
westerly winds and a gradual lifting of the cloud bases.

DTW THRESHOLD PROBABILITIES...

*  High in ceilings at or below 5000 ft Monday and Monday night.

*  High for ptype of rain Monday.

*  Low in crosswind thresholds being exceeded Monday night.


&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory from 1 AM Tuesday to 4 AM EST Wednesday for
     LHZ421-422-441>443.

Lake St Clair...Small Craft Advisory from 1 AM to 10 PM EST Tuesday for LCZ460.

Michigan waters of Lake Erie...Small Craft Advisory from 1 AM to 10 PM EST Tuesday for LEZ444.

&&

$$

DISCUSSION...MR
MARINE.......MV
AVIATION.....SC

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