000
FXUS63 KDTX 182308
AFDDTX
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
708 PM EDT Mon Mar 18 2024
.KEY MESSAGES...
- Reinforcing shot of arctic air for Wednesday and Thursday with
scattered snow flurries.
- Increasing likelihood for accumulating snowfall for Southeast
Michigan late Thursday night into Friday.
&&
.AVIATION...
The region of flurries/light snow showers will exit to the east of
metro Detroit around or shortly after 00Z as the axis of deep layer
moisture overhead departs. While the loss in diurnal heating will
offer some potential for partial clearing, westerly flow off Lake
Michigan will sustain occasional VFR based strato cu into the
overnight. The low level flow will back toward the southwest
overnight in advance of a cold front forecast to move into the
western Great Lakes. The low level airmass being advected into Se Mi
within this flow will be very dry. This will likely scour out much
if not all of the lower end VFR based clouds, leaving only higher
based mid clouds. The southwest gradient will quickly increase
during the morning. Model soundings also indicate steepening low
level lapse rates, aided by diurnal heating, with 25 to 30 knots
winds within the mixed layer. This will support ample gustiness to
the sfc winds during the daytime Tuesday. The sfc cold front is
forecast to track across the area late Tues afternoon, leading to a
veering of the winds to the west.
.DTW THRESHOLD PROBABILITIES...
* Moderate in ceilings aob 5000 feet this evening. Low overnight.
* Low in crosswind thresholds being exceeded Tuesday afternoon.
&&
.PREV DISCUSSION...
Issued at 302 PM EDT Mon Mar 18 2024
DISCUSSION...
Scattered flurries or snow showers will end this evening as weak
forcing settles south and diurnal instability ebbs, but additional
activity will be possible late tonight into Tuesday as isentropic
lift increases in advance of approaching clipper low pressure. This
will be focused mainly over the Thumb into Lake Huron on points
north and east with minor accumulations not out of the question.
Further south, expect only a few flurries at most. With this low
pressure taking a northern track, relatively mild southwesterly
winds will bring temperatures back into the mid 40s by afternoon.
Arctic high pressure will then settle back into the area midweek in
the wake of the next passing cold front Tuesday night to Wednesday.
Isolated to scattered flurries will be possible again with this next
reinforcing shot of colder air late Tuesday night into Wednesday
with dry weather expected Thursday as the high pressure begins to
build into the area. High temperatures will be below average during
this period with highs generally in the 30s.
A more significant Pacific shortwave is still expected to encroach
on the area late Thursday night into Friday. Some model differences
are beginning to emerge in terms of how amplified this system will
become (particularly in the H7-H85 layer) as it translates from the
northern plains into the southern Great Lakes and northern Ohio
Valley and interacts to a degree with base of Polar Vortex along the
southern shore of Hudson Bay as it wobbles south. Both timing and
north/south positioning of the main areas of lift will be impacted
by the eventual configuration of this system.
Assuming models trend to an increasingly amplified system (or at
least maintain the degree of amplification depicted in the more
aggressive 12z models), would expect a slightly slower progression
of snow into the area (mainly into Friday) and also a more northern
pivot of the best warm frontal forcing to the east and northeast of
the low pressure center. While this fluctuation in the degree of
system amplification complicates the forecast and lower confidence
in the location of best forcing (hence best snowfall rates), it does
still appear that widespread accumulating snow will occur. A later
start time into Friday of the best rates will likely cut into totals
somewhat given the late March timing, but 1-2 inches seem plausible
and the possibly for more than that cannot be ruled out.
The southern periphery of a bitterly cold arctic airmass settles
back into the area in the wake of this system so expect upper 30s to
lower 40s for high temperatures from north to south across the
forecast area during the upcoming weekend. With the arctic high
positioned to the north, dry weather is expected. A more active
pattern re-establishes early next week (possible as early as late
Sunday) as the next storm system spins up to the west and tracks
into the region. A plethora of solutions exist at the Day 7 time
frame as to how this system may evolve. Confidence in details, as
would be expected, is quite low at this time.
MARINE...
Northern edge of Mississippi river valley high pressure briefly
builds into the central Great Lakes tonight allowing for a very
shortlived respite in winds and waves. Developing southwest flow
quickly ramps up by early Tuesday morning ahead of a clipper system
likely requiring the (re)issuance of small craft advisories in the
Saginaw Bay and the MI waters of Erie. Aforementioned clipper drops
through the area daytime Tuesday bringing another round of snow
showers as well as drawing an arctic airmass into the Great Lakes.
Deepening low pressure over the Northeast in concert with this
colder airmass offers a window for potential NW low-end gales over
the northern half of Lake Huron daytime Wednesday. A Gale Watch is
now in effect for these waters for the majority of the day
Wednesday. Winds then weaken into Thursday as the east Coast low
slides into the Canadian maritimes.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from late Tuesday night through Wednesday evening for
LHZ361>363.
Small Craft Advisory from 6 AM to 4 PM EDT Tuesday for LHZ421-422.
Lake St Clair...None.
Michigan waters of Lake Erie...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LEZ444.
&&
$$
AVIATION.....SC
DISCUSSION...DG
MARINE.......KDK
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