Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 280511
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
111 AM EDT Thu Mar 28 2024

.KEY MESSAGES...

- Westerly lake effect snow continues tonight through Thursday
  evening, mainly across the Copper Country.
- Moderate to heavy lake effect snow and blowing snow is expected,
  mainly across the Copper Country through tonight.
- Heaviest snow amounts expected through tonight from Twin Lakes to
  Painesdale.
- Next chance of widespread precipitation occurs Friday night
  and Saturday, followed by a system worth monitoring for
  Monday/Tuesday next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 311 PM EDT Wed Mar 27 2024

Latest water vapor imagery and RAP analysis show broad troughing
over the Great Lakes, with an embedded closed low circulation moving
towards western Lake Superior. Chilly WSW flow with 850mb
temperatures around  -13 to -16C is keeping in lake effect snow
showers across the WSW wind snow belts across the western UP.
Occasionally heavier banding is apparent on satellite at times off
the Bayfield peninsula, directed into the Keweenaw. Meanwhile, with
the approaching midlevel low, widespread lower level stratocumulus
remains across most of the UP, with widely scattered flurries and
light snow showers.

With better mixing this afternoon courtesy of CAA and diurnal
instability, inversion heights are increasing in model soundings to
around 7kft with much of the mixed layer occurring in the DGZ. Still,
soundings are not overwhelmingly moist and there is an inverted-v
type signature below the cloud layer, which may be helping to cut
down on snowfall rates...at least, apart from where we are seeing
heavier banding. Thus, for the rest of the afternoon, across most of
the area may be fairly light, well below an inch. In the snow belts
of the western UP, a general 1-3in is more favored among guidance,
but higher embedded totals are possible where we are seeing heavier
banding into the area.

Soundings moisten up into the evening as the midlevel low heads into
the area. Crosshair signature is also noted in the model soundings
with the best model omega/lift intersecting the DGZ, maximizing snow
growth. As a result, expect LES accumulation to really take off as
we head closer to 00Z. HREF guidance shows a widespread quarter to
half inch/hr snowfall rates across the western UP, with higher
embedded rates up to 1in/hr from northern Houghton through southern
Keweenaw counties. This should bring in several more inches of
snowfall overnight, but this starts to taper off into the early
hours of Thursday as the low moves north of Lake Superior, inversion
heights begin to lower, and soundings start to dry out. Though the
heaviest snow totals will be in the western snow belts in the western
UP, but some light snow accumulations (generally a trace) are
possible across much of the UP at least through the first half of
the night with the low moving through. Expect another  4-8 inches of
snow overnight from the Porcupines northward through the Keweenaw,
with the highest amounts from Twin Lakes to Painesdale. This would
lead to event totals near a foot in the warning area from this
afternoon through early Thursday.

Meanwhile, increased mixing from the colder air is leading to
blustery west winds this afternoon, with gusts as high as 30-40 mph
at times across portions of the Keweenaw, exacerbating occasional
whiteout conditions in blowing snow. Elsewhere, gusts are staying in
the 20-30mph range. Wind gusts fall back into the night, with most
of the area gusting up to 20mph and higher gusts around 20-30 mph
more common in the Keweenaw.

With blowing snow and a potential for several more inches of snow
across the western UP, our winter headlines remain in place through
Thursday morning.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 249 PM EDT Wed Mar 27 2024

Medium range guidance continues to handle the overall theme in the
extended forecast period well, presenting a consistent picture of
the main features in play going into the weekend. Starting off on
Thursday, the mid-upper level low that`s been responsible for the
snow and rain these past few days will continue its northeastward
exit toward James Bay while increasing anticyclonic flow and ridging
builds across the Plains. At the surface, high pressure will press
into western Wisconsin through the day, helping to pull in dry air
and subsidence that will result in diminishing lake effect snow
activity for the west wind snow belts. While the trend will be
decreasing activity, another inch or two of snow should be expected
in the Copper County, with the highest amounts being along the Spine
of the Keweenaw. Elsewhere, mostly dry conditions are expected.
Daytime highs should climb into the 30s, maybe near 40F for the
southern portions of Menominee County. The dry conditions will
persist overnight and Friday. Overnight lows should be mostly in the
teens interior west and low to mid 20s elsewhere. Daytime highs
Friday should top out in the 40s except mid to upper 30s near Lake
Superior and in the Keweenaw.

During the day on Friday, the mid-level ridge axis will shift
through the region as a surface low organizes in the Central Plains
and a northern stream shortwave presses through the Northern Tier
along the international border. As these features move into the
Upper Great Lakes, precip will move into the forecast area. Timing
among the various guidance packages suggest increasing precip
chances Friday evening that should persist through Saturday as the
surface low lifts through southern Lake Michigan and southern Lower
Michigan and the attendant inverted trough moves through Upper
Michigan. Precip type appears to be a mix of rain, snow, and maybe,
freezing rain, at least early on. As the event progresses through,
warm nose feature around 2-3k feet should break down as weak cold
air advection sets up. This should help any precip transition over
to rain or snow. Precip should come to an end Saturday evening,
followed by a dry Sunday thanks to another surface high moving
through the region.

Attention then shifts to a the potential interaction of a trough
exiting the Rockies and shortwaves dropping out of Canada. Model
trends with this system appear to be moving south and there is a
general trend toward potential phasing with a shortwave late Monday
and Tuesday. GEFS and EC ensemble systems continue to suggest weak
clustering of their membership and both their ensemble means move
the surface low near southern Lake Michigan and into southern Lower
Michigan. The same ensemble systems suggests the greater probability
of moderate QPF being near the ensemble means. This suggests a
significant precipitation event/snow event is becoming less likely,
but certainly continues to warrant monitoring in the coming days.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 111 AM EDT Thu Mar 28 2024

The lake-effect snowfall will gradually dwindle throughout the TAF
period over the west snow belts as ridging builds in from our west.
While KIWD hangs on to MVFR cigs early this morning, expect it to
improve to VFR before dawn this morning as the cloud cigs lift due
to the departing low. That being said, we could (50% chance) see
MVFR cigs return again for a few hours over KIWD late this morning
before settling into VFR conditions for the rest of the TAF period.
As for KCMX, IFR conditions are expected to continue early this
morning due to the continuing lake-effect snow. With most of the
CAMs showing the snowfall rates lightening up after 8 AM EDT, I`m
thinking we will see an improvement to MVFR conditions by late this
morning over the Keweenaw; we could even see VFR conditions return
this evening as the peak of the incoming ridging moves into the far
western U.P. As for KSAW, expect VFR conditions across the TAF
period. While some blustery westerly winds could be seen early this
morning, winds look to weaken by this evening as the ridging moves
in.

&&

.MARINE...
Issued at 249 PM EDT Wed Mar 27 2024

Strong, mostly westerly and southwesterly winds will persist this
afternoon and evening as a surface low slowly pulls away into Hudson
Bay, leaving behind continued lake-induced instability and modest
pressure gradient forces thanks to high pressure building in across
the Plains. Expecting today`s low end gales to lighten through the
night as these forces begin balancing, but given the persistent
colder airmass aloft, near 30kt gusts should be expected at least
through Thursday. The colder airmass and wind will also make
freezing spray accumulation possible, although the trend to weaker
winds should reduce the risk through late tonight into Thursday. No
changes were made to the current gale warnings. Winds lighten to
around 20kts or less Thursday night, then remain light going into
the weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory until 8 AM EDT this morning for MIZ001-
     002.

  Winter Storm Warning until 8 AM EDT this morning for MIZ003.

Lake Superior...
  Small Craft Advisory until 8 PM EDT /7 PM CDT/ this evening
     for LSZ240>244.

  Small Craft Advisory until 8 AM EDT this morning for LSZ249.

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

Lake Michigan...
  Small Craft Advisory until 2 AM EDT early this morning for
     LMZ221-248-250.

&&

$$

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


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