Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 180701
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
301 AM EDT Mon Mar 18 2024

.KEY MESSAGES...

- Lake enhanced/effect snow into Monday. The western U.P. near Lake
  Superior, and Baraga, Alger, and northern Schoolcraft counties
  could see an additional fluffy 2 to 4 inches.
- A prolonged gale event on Lake Superior is expected to end tonight.
- Blustery northwest to north winds continue today before
  calming down tonight.
- The snow today into tonight, combined with blustery winds,
  will result in some hazardous driving conditions.
- Light snow possible Tuesday followed by another lake effect
  snow event through early Thursday.
- Blustery winds return Tuesday night and Wednesday.
- Northwest gale force winds and heavy freezing spray possible Tuesday
  night and Wednesday across eastern Lake Superior.

&&

.SHORT TERM /THROUGH THIS AFTERNOON/...
Issued at 301 AM EDT Mon Mar 18 2024

Upper air pattern consists of a 500 mb trough and closed low over
the desert sw and a ridge over the Pacific NW with a deep trough
over the eastern U.S. The deep trough moves east and narrows over
the eastern U.S. today with upper ridging starting to move into the
upper Great Lakes by 00z Tue. DGZ continues to be in the cloud layer
below the inversion which is at 5000 feet, but inversion falls today
below 3000 feet, so until the wind backs to the west and southwest
which is late this afternoon, the light snow showers will continue,
but pops will decrease. This is covered well in the forecast, but
did hang on to pops longer in the west and the Keweenaw as models
tend to end it quicker than what actually happens.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 342 PM EDT Sun Mar 17 2024

The broad ridge extending up the west coast and downstream troughing
extending down the east coast will position Upper Michigan within
northwest flow through the first half of the work week, subjecting
the forecast area to the impacts of any clipper system riding the
ridge southeast into the trough. In terms of sensible weather, this
means snow chances, more winter like temperatures, and gusty winds.
Toward the end of the week, there`s a potential for the pattern to
shift to more zonal flow; however, confidence is low given the broad
and longitudinally elongated negative height anomaly stretching
across most of Canada and an eastward progressing deep trough into
the west coast. Overall, this results in less confidence in the
forecast for this weekend.

Tonight, a surface high sprawled out over the Northern Plains will
continue to spread eastward towards the Great Lakes. Lake effect
snow showers continue into early MOnday, but should gradually wind
down through the morning with increasing subsidence and lowering
inversion heights courtesy of drier air working in. By afternoon,
most of the area should be dry with just some isolated snow shower
activity lingering across the eastern UP. Additional light snow
totals generally below an inch are expected Monday, but some 1-2in
amounts are possible across Alger county.

Monday evening, a shortwave/clipper system will exit Canada into
northern Minnesota. As it moves into the Upper Great Lakes, light
snow will move in from northwest to southeast. Through the day on
Tuesday, a secondary surface low will slowly move eastward just
north of Lake Superior while a secondary shortwave drops into the
region. As this pulls away, a tighter pressure gradient will develop
over the region as cold air advection sweeps south. In effect, this
will develop lake effect snow showers and support blustery
conditions the rest of the day Tuesday, continuing into Wednesday.
An inverted surface trough should gradually take form across eastern
Lake Superior, sustaining shower activity across eastern Upper
Michigan into early Thursday. High pressure shifts east through
Ontario during the day Thursday, working to diminish snow shower
activity for most of the area.

At this point, guidance begins to vary as the broad trough over the
east coast begins lifting while another closed low drops into
northern Manitoba, reinforcing the negative height anomaly across
Canada. Guidance remains in disagreement on whether another
shortwave ejecting out of the northern Rockies will get caught up in
this broad circulation. If it does, another round of precip could
move into the region Thursday night; if it doesn`t, then this
impulse should remain too far south to impact us. The same level of
uncertainty exists for another wave Friday night into Saturday, then
we look ahead to another low pressure system deepening over the
Plains Sunday into Monday that could bring another round of wintry
weather into early next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 116 AM EDT Mon Mar 18 2024

Ongoing lake enhanced snow off of Lake Superior is diminishing and
will continue to do so overnight as a drier air mass begins to
overspread the area. That said, lake effect shsn/flurries won`t
completely end until passage of sfc high pres ridge today. At IWD,
expect MVFR to prevail thru this morning with -shsn diminishing to
flurries by sunrise. Lingering flurries will end, and MVFR cigs will
clear out to VFR early to mid aftn. At CMX, expect MVFR to prevail
thru today with -shsn diminishing to flurries this morning.
Lingering flurries will end, and MVFR cigs will scatter out to VFR
this evening at CMX. However, next approaching disturbance will
likely bring a period of -sn and MVFR conditions to CMX late
evening. At SAW, MVFR will prevail thru today, though a period of
IFR cigs is possible overnight. Ongoing -shsn will diminish to
flurries this morning, then end in the aftn. The MVFR cigs will
clear out to VFR at SAW this evening.

&&

.MARINE...
Issued at 342 PM EDT Sun Mar 17 2024

Northwest gales of 35-40kts continue mainly across the eastern half
of the lake the rest of today before slowly falling back below gale
force through the first half of tonight. A few gale force gusts are
not out of the question in western Lake Superior as well, but
confidence is low (around 20%). Winds continue to fall below 30
knots by Monday morning.

Light winds should persist the rest of Monday through Tuesday
morning. Another system moving through the region then will bring
another punch of colder air and tighter pressure gradient, with the
threat for gales across the east half increasing Tuesday night into
Wednesday. Internal probabilistic guidance shows around 80-90%
chance for gales beginning Tuesday night, with a low chance (20-40%)
for high-end gales developing Wednesday afternoon. Additionally,
with this trend and the colder airmass, heavy freezing spray is
appearing to be more likely. Winds decrease Wednesday night, coming
in at or below 20 knots the rest of the week.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
  Small Craft Advisory until 11 AM EDT this morning for LSZ246-
     247.

  Small Craft Advisory until 2 PM EDT /1 PM CDT/ this afternoon
     for LSZ240>242.

  Small Craft Advisory until 5 PM EDT this afternoon for
     LSZ243>245.

  Gale Watch from Tuesday evening through Wednesday evening for
     LSZ243>251-264>267.

  Small Craft Advisory until 11 PM EDT this evening for LSZ248-
     249.

  Small Craft Advisory until 2 AM EDT Tuesday for LSZ250-251.

Lake Michigan...
  Small Craft Advisory until 11 AM EDT this morning for LMZ221-
     248-250.

&&

$$

SHORT TERM...07
LONG TERM...LC
AVIATION...Rolfson
MARINE...LC


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