Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 011101

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
601 AM EST Mon Mar 1 2021


Morning satellite trends showing a fair amount of breaks in the
clouds with a continued decrease in coverage as cold, dry air pushes
through southeast Michigan. The result will be a mix of MVFR/VFR
conditions this morning. Clouds then increase in coverage during the
afternoon as the lakes remain somewhat activated by a reinforcing
shot of cold air along with daytime heating. These streaming stratocu
will continue to be borderline MVFR/VFR and have potential to
produce some flurries as steep boundary layer lapse rates develop
during the day. Given the amount of dry air and anticipated limited
coverage, will leave mention out of TAFs at this time. Northwest
winds remain gusty today as mixing depths increase to around 3kft and
lead to gusts around 25 knots.

For DTW...Northwest winds (280-310) will be gusting to near 30 knots
this afternoon and likely exceed crosswind threshold by around 16Z
and continue until about 23/00Z when winds begin to gradually
decrease through the remainder of the evening. Cold, dry air will
bring SCT/BKN coverage of low clouds at 2-4 kft this morning before
afternoon redevelopment leads to greater coverage of borderline
MVFR/low VFR ceilings. Low chance a few stray flurries affect the
terminal this afternoon, but too low of a chance to mention in TAFs
at this time.


* Moderate to high for exceeding crosswind threshold from 280-300
  late this afternoon.

* Moderate for ceiling 5000 ft or less this afternoon.


Issued at 301 AM EST Mon Mar 1 2021


An amplifying mid level trough axis, an extension of the polar low
over northern Canada, will rotate from nrn Ontario and Lake Superior
early this morning before reaching southern Quebec as a closed
circulation by evening. This track will keep the core of the arctic
air north and east of Se Mi. It will still however deliver a fairly
robust shot of arctic air into the srn Great Lakes today; 850mb
temps into the negative teens by late afternoon. The strongest push
of cold air will occur between 15Z and 19Z with the passage of the
arctic cold front. The depth of the cold air advection and early
March diurnal heating will boost mixing depths. The RAP is
suggestive of mixing depths up to 6k feet with 25 to 30 knots in the
mixed layer. This will support frequent wind gusts in the 25 to 35
MPH range throughout the late morning and afternoon. Temps are
likely to make some rebound into the low to mid 30s across metro
Detroit and points south before dropping into the 20s later in the
afternoon. Rap and NAM soundings suggest the earlier arrival of the
cold air to the north will lead to an overall gradual drop in temps
through the 20s during the day.

While the cold air advection is already producing a decent moisture
flux off the lakes, ongoing dry air advection looks to limit the
snow shower potential across Se Mi today. Some DCVA and upper jet
support now leading to a region of light snow across central
Minnesota is forecast to weaken considerably as it approaches srn
Lower Mi by early afternoon. Per model soundings, there looks to be
just enough moisture atop the mixed layer to support some scattered
light snow showers and/or flurries today; the greatest coverage of
which looks to be across the thumb with getter influence from
northern Lake Michigan in the northwest flow.

Strongly confluent mid level flow will then take hold across Lower
Mi this evening into the overnight as the mid level low quickly
moves from southern Quebec to New England. This will drive surface
high pressure across the northern Ohio Valley and far southern Lower
Mi. It will take well into the night before the gradient flow
weakens enough to support decent radiational cooling. So min temps in
the upper single digits to mid teens looks reasonable despite the
degree of cold air overhead.

The surface high will be suppressed to the south on Tuesday as a mid
level short wave impulse and associated surface low tracks into
northern Ontario. This will strengthen the southwest flow across the
Great Lakes and support a decent warm air advection regime. The
warming in the 900 to 800mb layer will be enough to limit mixing
depths. Nonetheless, Tuesday highs should make a run a 40 degrees
under breezy conditions. The passage of the aforementioned short
wave to the north will drive a back door cold front into srn Lower
Mi on Wednesday. Location of these features this time of year are
always challenging as they tend to accelerate down Lake Huron.
Based on model consensus, forecast high across the south will remain
well in the 40s on Wed, with cooler conditions across the thumb.
Very limited moisture will at least sustain a dry forecast. High
pressure will sustain dry conditions into the weekend. Long wave
trough amplification across eastern Canada late in the week will
support temps slightly on the cool side of early March averages late
in the week and through the weekend.


Cold advection is underway across the central Great Lakes this
morning. Northwest gales or near-gales are likely to continue
through the morning across northern and central Lake Huron while
gusts up to 20 to 30 kt elsewhere generally weaken for a brief
period this morning. Another strong cold front drops across the
region today and brings in a fresh surge of arctic air. The ensuing
cold advection reinforces steep near-surface lapse rates and brings
another period of gales this afternoon and evening for
northern/central Lake Huron, as well as snow showers and freezing
spray. The Gale Warning remains in effect until late this evening.
Small Craft Advisories are also in effect along the Lake Huron
nearshore zones around the Thumb for waves building into the 4 to 6
foot range. High pressure then slides across the southern Great
Lakes Tuesday morning which swings winds around to the southwest.
Another period of near-gale gusts is possible Tuesday evening ahead
of the next low set to track into the northern Great Lakes Tuesday


Lake Huron...Small Craft Advisory until 9 PM EST Tuesday for LHZ421-441.

     Small Craft Advisory until 4 AM EST Tuesday for LHZ442-443.

     Gale Warning until 10 PM EST this evening for LHZ361>363.

Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.



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