Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 242326
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
726 PM EDT Sun Mar 24 2024

.KEY MESSAGES...

- Late season winter storm lifting northeast from Colorado brings
accumulating snow and hazardous travel this afternoon into Monday.
- Gales are expected across Lake Superior Monday into possibly
Tuesday.
- Westerly lake effect snow develops early Wednesday morning and
continues through Thursday evening, mainly across the Copper Country.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 357 PM EDT Sun Mar 24 2024

RAP analysis has a deepening surface low over eastern CO this
afternoon, with tight southerly flow out ahead of it leading to
robust WAA into the Great Lakes. A strong 40-55kt 850mb LLJ is
draped across the Plains, with the exit region directed northeast
IA. Light snow has spread into the Great Lakes with modest WAA and
isentropic ascent. However, the steadier snowfall remains well to
our southwest so far, across central MN to western WI on the nose of
the jet. Will note a heavier band moving through northern IA at this
time where 850mb frontogenesis is maximized. There are also a couple
of prominent dry slots noted on water vapor imagery; the first is
working through SW MN behind the leading swath of steady snowfall,
and the second moving northward through eastern IA behind the narrow
band of heavier snow.

Weak radar returns are apparent across the UP, with plenty of ASOS
sites reporting snow on and off as well as brief drops in
visibility. So, expect flurries and light snow to continue the rest
of the afternoon before steadier snowfall starts to move in just
before 00Z. Guidance remains in fairly good agreement on QPF amounts
up to a tenth of an inch by 00Z, highest along the WI border; with
SLRs still around 14:1, this should result in a quick half to 1.5 in
of snow into the evening.

Steadier snowfall arrives after 00Z as the stronger ascent reaches
the area. HREF snowfall rates continue to favor widespread quarter-
to half-inch per hour snowfall rates across the central and western
UP from around 00-09Z, and several hours of higher rates up to 1-
1.5in/hr from around 03-08Z as the heavier band currently moving
through IA on the back edge of the main precip shield arrives.
Simulated reflectivity does indicate that this band washes out
somewhat while lifting through WI, with only around a 40% chance of
those higher snowfall rates being realized as the band pivots into
the UP. Snow quickly tapers off across the eastern UP the second
half of the night as the warm front lifts to the NW and the dry slot
moves in from the southeast, but snow will continue across the far
western UP. SLRs remain quite low with a narrow DGZ up above 10kft
in soundings, and quite warm (though sub-freezing before 12Z)
profiles. Ratios starting off around 10-14:1 before 06Z begin to
fall below 10:1 the second half of the night. With widespread QPF
amounts up to a quarter to half an inch to the west, and up to a
quarter inch in the east, we should be looking at snow totals
generally around 4 to 8 inches for much of the western UP. Higher
embedded amounts up to 10in are possible particularly throughout the
Keweenaw, where colder profiles lead to higher SLRs. Lighter snow
totals around 1-3in are expected across the eastern UP. With no real
major changes to the timing and snowfall totals, our current
headlines will remain intact.

Otherwise, expect temperatures to largely hold steady overnight,
hovering in the upper 20s to lower 30s. Stable soundings indicated a
limited potential for us to tap into the stronger winds arriving
aloft tonight, but we could still see some 20mph gusts heading into
the second half of the night.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...
Issued at 316 PM EDT Sun Mar 24 2024

The long-term forecast starts off continuing the precipitation
across the area due to the vertically-stacked low lifting through
the Plains towards western Lake Superior. While we will likely see
some snow initially over the western half of the U.P., with the warm
nose continuing northwards across the area throughout the day,
expect the progressive transition over to rainfall from the
southeast to northwest throughout the day Monday. In addition, some
recent CAMs such as the 12z HRRR are highlighting the dry layer in
the lower levels being stronger and moving a little further west
than previously anticipated. Thus, precipitation chances look to be
fairly limited (around 10 to 40% chance) Monday morning into early
Monday afternoon over the eastern half. As we see the transition
from snow to rain across the area Monday, we could see a wintry mix
of sleet and freezing rain Monday morning into Monday afternoon over
the higher elevations of the western U.P. in-between the snow and
rain. While a subtle shortwave lifts around the vertically-stacked
parent low towards our area late Monday, with the dry slot in the
lower levels `eating away` much of the precipitation potential,
icing and sleet accumulations look to be fairly minimal. Indeed, by
the time some of the CAMs show freezing rain over the higher
elevations over the western U.P., there is a diminishing window of
negative energy near the surface in comparison to a growing layer of
positive energy aloft within the atmosphere. Thus, with surface
temperatures likely to be near freezing already, the sun being out
(although cloud covered), and with an ever shrinking negative energy
layer overhead, I`m thinking icing accumulations will be no more
than a glaze and mostly on elevated surfaces and the snowpack that
will have developed by then. That being said, it could make for an
extra slick spot here or there on the untreated roadways across the
higher elevations, particularly the Keweenaw where the colder
temperatures are looking to hold on the longest.

Moving into Monday night and Tuesday, expect pure rainfall across
the area as we will reside in the warm-sector of the parent low by
then. Two shortwaves look to rotate around the parent low Monday
night through Tuesday, with the first shortwave bringing light to
occasionally moderate rainfall at times, particularly over the
western U.P. where a local deformation band could set up. In
addition, some locally higher rainfall rates could be seen near Lake
Michigan due to some slight upslope flow that could occur. Behind
this shortwave, the second shortwave looks to lift up into the area
Tuesday and bring some additional light rainfall across the area
(there won`t be as much moisture available in the atmosphere by
then), save for the south wind lake-effect belts over the eastern
U.P.; this area could see some locally moderate rainfall at times as
a deformation zone could enhance the rain rates. By the late
afternoon Tuesday, the cold air advection behind the parent low
begins to work its way into our far west by Ironwood, transitioning
any remaining rainfall back over to snow showers through Tuesday
night.

As the parent low continues lifting through northern Ontario
Wednesday, some lake-effect/enhanced snow showers are expected
across mainly the west snow belts as delta Ts across Lake Superior
drop to the upper teens to around 20C behind the wake of the low. In
addition, there is a chance (30%) that some scattered snow showers
will traverse from west to east across the interior areas of the
U.P. Wednesday if the comma-head of the low is south enough to be
over us during the day. While only light snowfall is generally
expected for the area, we could see some locally higher snow totals
across the Keweenaw as some of the medium range guidance hint at a
possible (30%) convergent band setting up over the area. A secondary
shortwave low rotating around the parent low looks to keep the lake-
effect snowfall over the west snow belts going late Wednesday night
through Thursday. As ridging builds into the region Thursday night
into Friday, expect the lake-effect snowfall to slowly end from west
to east while transitioning to the northwest snow belts.

Moving into next weekend, expect temperatures near normal. While we
could see an additional shot for precipitation sometime during the
weekend, with model guidance kind of being all over the place right
now, the confidence in precipitation chances is rather low at this
time (around 30-ish% chance).

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 726 PM EDT Sun Mar 24 2024

Snow will continue overnight with IFR conditions expected at all
sites. IFR conditions will last through the period at IWD. IWD could
also briefly see some freezing rain Mon morning before a rain and
snow mix occurs before becoming all rain by late Mon afternoon. At
CMX, LIFR will move in by Mon afternoon with snow changing over to
rain by mid afternoon. At SAW, dry slot comes in later tonight and
snow will end and conditions will go VFR late tonight. Rain moves
back in at SAW by Mon afternoon and will go back to IFR.

&&

.MARINE...
Issued at 316 PM EDT Sun Mar 24 2024

East to southeasterly winds are increasing this afternoon through
tonight as a warm front moves into the Upper Midwest, with winds
reaching speeds of 20 to 30 knots by midnight tonight. As the warm
front begins moving into Lake Superior tonight into Monday, winds
slowly continue increasing, with some gale force gusts being seen
from time to time during the morning hours along the International
Border and western lake as some mixing occurs within the first 500
to 1000 feet up from the surface. As the mixing continues and the
warm front continues advecting over Lake Superior, more consistent
gales of 35 to 40 knots begin occurring by the afternoon hours
Monday. As the parent low begins lifting towards western Lake
Superior Monday night into Tuesday, the winds over the western half
of the lake begin to back to the northeast and weaken. Meanwhile,
some of the CAMs are showing some sharp increases in the wind gusts
along the International Border to Whitefish Bay Monday night into
Tuesday morning, especially the Hires-FV3 and the HRRR. While I do
have my reservations due to mixing likely (70% chance) being limited
due to the temperature inversion just above the surface by this
time, if the funneling due to a convergence of the winds is strong
enough, some gales are certainly possible (50% chance). As the low
continues into northern Ontario Tuesday evening, the southeasterly
winds over the eastern lake weaken whereas cold air advection behind
the low will increase winds to generally 20 to 30 knots from the
northwest over the west half. As cold air advection continues to
spread across the lake into Wednesday, winds back to the west at
around 30 knots. That being said, some gales up to 35 knots are
possible (40 to 50% chance) near the Keweenaw Wednesday. A secondary
shortwave low rotating over Lake Superior Wednesday night into
Thursday looks to keep westerly winds of 20 to 30 knots going. By
Friday, the winds are projected to weaken to 20 knots or less as
ridging moves back across the Upper Great Lakes.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Warning until 2 PM EDT Monday for MIZ001-003.

  Winter Weather Advisory until 2 PM EDT /1 PM CDT/ Monday for
     MIZ002-004-005-009>012-084.

  Winter Weather Advisory until 5 AM EDT Monday for MIZ006-013-
     014-085.

Lake Superior...
  Small Craft Advisory until 11 AM EDT Monday for LSZ244.

  Small Craft Advisory until 8 PM EDT Tuesday for LSZ245.

  Gale Warning from 8 AM EDT /7 AM CDT/ Monday to 2 PM EDT /1 PM
     CDT/ Tuesday for LSZ162-263.

  Small Craft Advisory from 8 AM EDT /7 AM CDT/ Monday to 8 PM
     EDT /7 PM CDT/ Tuesday for LSZ240-241.

  Small Craft Advisory from 8 AM to 8 PM EDT Monday for LSZ242.

  Small Craft Advisory from 2 AM Monday to 8 PM EDT Tuesday for
     LSZ243.

  Gale Warning from 11 AM Monday to 2 PM EDT Tuesday for LSZ244-
     264.

  Small Craft Advisory until 2 PM EDT Tuesday for LSZ246>248.

  Small Craft Advisory from 5 AM to 2 PM EDT Monday for LSZ249-
     250.

  Small Craft Advisory until 2 PM EDT Monday for LSZ251.

  Gale Warning from 2 PM Monday to 2 PM EDT Tuesday for LSZ251-
     266-267.

Lake Michigan...
  Small Craft Advisory until 11 AM EDT Monday for LMZ221.

  Small Craft Advisory from 2 AM to 8 PM EDT Tuesday for LMZ221.

  Small Craft Advisory until 8 PM EDT Tuesday for LMZ248-250.

&&

$$

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


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