Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 180340
AFDDTX

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1140 PM EDT Sun Mar 17 2024

.KEY MESSAGES...

- Below average temperatures into Monday with scattered flurries
  and snow showers.

- Reinforcing shot of arctic air for Wednesday and Thursday with
  some potential of accumulating snow by week`s end.

&&

.AVIATION...

A trough axis and region of deeper moisture will advance across Se
Mi from the north this morning. This will sustain flurries and some
light snow showers this morning. Inversion heights remain high
based, so ceilings will remain predominately VFR. There may however
be a few brief intervals of MVFR in any higher intensity snow
showers. Increased convective depth through diurnal heating late
this morning and afternoon will deepening the convective depths and
will support some increase in the coverage of snow showers.
Convective depths are not expected to be as great as Sunday
afternoon, so snow showers are not expected to be as intense. The
deepening of the mixed layer will also increase WNW wind speeds a
bit, supporting some gusts over 20 knots.

.DTW THRESHOLD PROBABILITIES...

* High in precip type being snow tonight and Monday.

* Moderate in ceilings aob 5000 tonight and Monday.

&&

.PREV DISCUSSION...
Issued at 314 PM EDT Sun Mar 17 2024

DISCUSSION...

Localized forcing in advance of compact shortwave disturbance now
crossing central Lake Michigan will expand east through the forecast
area during peak heating/instability late this afternoon. This will
lead to an expansion of scattered snow shower activity (compared to
the more isolated light snow shower/flurry activity for much of the
day) which should hold into early evening before fading quickly
after sunset.

A surface trough will then clip the area overnight tonight with the
main forcing (and snow shower activity positioned to the northeast
over Ontario/Lake Huron into parts of the Thumb). Cold air advection
in behind this feature will also maintain the chilly early spring
conditions with low temperatures in the mid 20s late tonight and high
temperatures in the mid to upper 30s again on Monday. At this time,
flurry/scattered snow shower activity looks to be more isolated in
nature on Monday. That said, will add low (slight chance) pops or at
least scattered flurry mention for the afternoon as diurnal cycle
acts to enhance the lake effect streamers that will be in place to
the northwest within this next reinforcing shot of cold northwest
flow.

A more organized clipper shortwave with an attending surface low
pressure system will then progress into the area late Monday night
into Tuesday as cold, northwesterly upper flow persists. While most
coarser model data keep most of the forcing with this system to the
north, first glance at HiRes models suggest flurries/snow showers
will be possible with isentropic ascent within area of warm air
advection pivoting around the base of this low pressure with some
chance of deformation clipping the northern forecast area as well as
the wave digs into the central Great Lakes. This sequence will occur
from late Monday night into mainly the first half of Tuesday. Given
the track of the center of this system to the north, a brief
moderation in temperatures is expect with highs in the 40s most
locations on Tuesday.

A much colder airmass descents through southeast from central Canada
into Ontario and Quebec and to a degree the Great Lakes. While the
coldest core of this airmass (-25C/-30C at H85) will remain north of
the Great Lakes, expect a return to high temperatures in the 30s to
around 40 Wednesday and lower/mid 30s Thursday. Meanwhile, 20s will
be common for low temperatures with teens even likely early Thursday
morning. This will be a quiet period in terms of the weather though
as sprawling surface high pressure builds into the region.

A shortwave of Pacific origin (currently over the north central
Pacific south of the Aleutian chain per GOES West Full Disk imagery)
will eventually track along the tight baroclinic zone left in place
by this passing arctic airmass. Medium range models are actually in
surprisingly good agreement on setting up an FGEN forcing type event
somewhere in the general vicinity as this wave encroaches Thursday
night into Friday.

If there is a notable system to track during the upcoming week, this
will be the one as a favorable track would bring the potential for
widespread measurable snow accumulation. Despite higher than average
confidence in having a system in the general area, the confidence in
the precise north to south positioning of what will be a relatively
narrow west to east band of enhanced precipitation remains low.

MARINE...

Cold air advection in the wake of the exiting low now positioned
over Quebec will lead to unstable conditions. Gusty winds will get a
boost tonight behind another cold front becoming northwesterly to
around 25 knots.  These winds and increased cold air advection will
help drive wave heights up through Monday thus a Small Craft
Advisory is in effect for Saginaw Bay and most of the nearshore
waters of Lake Huron. Area of high pressure slides in Monday night
and Tuesday leading to improved conditions but a clipper will then
dive southeast through the region Tuesday night and Wednesday
bringing a potentially colder airmass and stronger winds which may
reach gale force.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Small Craft Advisory until 4 PM EDT Monday for LHZ421-422-441.

     Small Craft Advisory from 10 AM to 4 PM EDT Monday for LHZ442.

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

$$

AVIATION.....SC
DISCUSSION...DG
MARINE.......DG


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