Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 240519
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
119 AM EDT Sun Mar 24 2024

.KEY MESSAGES...

- A brief period of quiet and dry weather continues through tonight.
- Late season winter storm lifting out of Colorado through the
  early part of the coming week will bring accumulating snow
  late Sunday into Monday morning.
- Heaviest snow accumulations will be Sunday night, resulting in
  hazardous travel into early Monday before a transition to rain
  during the day Monday.
- High end east to southeasterly gales are expected across Lake
  Superior Monday into Monday night.
- Westerly lake effect snow, mainly for the Copper Country
  Wednesday into Thursday.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 217 PM EDT Sat Mar 23 2024

Water vapor imagery and RAP analysis show mid-level troughing over
central and eastern Canada, anchored by a deep mid-level low
centered on the Hudson Bay shore of Ontario. At the surface,
sprawling surface high pressure centered over Manitoba is building
into the Great Lakes.

In spite of very dry midlevel air, lake-induced stratocumulus is
apparent on satellite courtesy of chilly NW flow over Superior
(850mb temperatures hovering around -18 to -20C). The Day Cloud Type
RGB shows higher cloud tops across the eastern UP, with a longer
fetch off of Superior. There, weak, cellular, lake-induced snow
showers are apparent on radar with some drops in visibility noted in
ASOS sites as well. Elsewhere, lower-topped, patchy strato-cu across
much of the western and central UP, becoming somewhat more organized
over Marquette county along the lake breeze. Precipitation has yet
to develop there, but will not rule out some light snow showers as
cloud tops do appear to be climbing. Totals across northern
Marquette county and across the eastern UP should only peak at
around a quarter to half an inch, with just isolated flurries and
snow showers elsewhere. Otherwise, temperatures are climbing through
hte 20s this afternoon, and should peak in the upper 20s and lower
30s across most of the area.

Any lingering flurries should end by sunset. The surface high
continues drifting eastward overnight, resulting in a wind shift
over mainly to the SE. With 850mb temps across northern Lake MI
around -12C, some flurries may develop into portions of central
Upper MI late tonight. Otherwise, expect midlevel cloud cover to
increase from the south courtesy of warm air advection ahead of the
much-advertised deepening low pressure system over the Plains.
Precipitation should hold off until after 12Z Sunday. Increasing
clouds and a shift over to southerly flow likely means that
overnight lows will occur fairly early in the night; expect most of
the area to fall into the teens, with some cooler pockets possibly
bottoming out in the single digits by 06Z. After that, temperatures
hold steady and perhaps even increase towards morning.

&&

.LONG TERM /SUNDAY THROUGH SATURDAY/...
Issued at 357 PM EDT Sat Mar 23 2024

The long-term forecast is mostly dominated by the presence of a low
pressure lifting through the Plains into Canada. As this low
continues its northward journey, the warm front moves through late
Sunday through Monday. This warm front initially brings snowfall
across the area Sunday night before transitioning to all rain Monday
(there could be a wintry mix of sleet/freezing rain over the
interior west mid-Monday). The rain continues into Tuesday before
the cold front of the parent low transitions what`s left of the
precipitation back over to snow late Tuesday. Afterwards, we could
see some lake-effect snow over the west snow belts, particularly the
Keweenaw, Wednesday into Thursday. Some more normal to above normal
temperatures and additional synoptic precipitation could return late
this upcoming week.

A surface high pressure ridge around 1030mb moving into Quebec
Sunday in conjunction with the deepening low off the Colorado
Rockies looks to increase southerly flow across the area, eventually
becoming southeasterly late in the afternoon. While antecedent dry
air near the surface should keep any snowfall aloft from hitting the
ground, it`s not likely but still possible (20 to 30% chance) that
we see some light snow develop over the higher elevations over the
western U.P. and the south/southeasterly flow upslope areas Sunday
morning into early Sunday afternoon. However, as the warm front of
the parent low (in Colorado at this time) begins to lift towards
Upper Michigan late Sunday, expect to see snow chances increase from
our southwest to northeast throughout the afternoon to evening
hours.

We expect most of the winter weather/snowfall impacts to be felt
across the area Sunday night when the brunt of the warm front makes
its way across Upper Michigan. Some impressive frontogenesis and
isentropic lift will allow moderate to heavy snowfall rates to
develop over Upper Michigan throughout the overnight hours; the HREF
hourly mean snowfall rates generally range from half to 1 inch per
hour rates, with the stronger snowfall rates being seen over the
western U.P. While the atmospheric thermal profile would initially
suggest high SLRs, with model soundings showing turbulence
developing within the warm front (causing snow crystal fracturing)
and warming temperatures within the profile, I`ve slightly lowered
SLRs even further down to generally 12:1 in the evening hours to
10:1 late during the night. CAMs show a dry slot working its way
into Upper Michigan late Sunday night from the southeast to
northwest within the warm front. This dry slotting will work to keep
snow totals lower over the eastern U.P. However, with snowfall
lasting longer over the western U.P. Sunday night into Monday
morning, the snow totals are project to be higher. Therefore, I`m
thinking we could around 2 to 5 inches of snow over the east and
around 5 to 7 inches over the west before we get into the daylight
hours Monday morning; there could locally be more over the Keweenaw
as some southeasterly lake-enhancement could come into play. The
slick roads and accumulating snowfall could make travel hazardous
over the western U.P. by Monday morning.

Monday`s forecast is a bit tricky as the parent low lifts through
northwestern Iowa. What model and ensemble guidance is agreeing on
is that we should see an anomalously high amount of precipitation
across most of our area Monday into Tuesday (see the ECMWF EFI for
instance). And the guidance suggests that eventually we will see a
transition from snowfall to rain across the area Monday. However,
what`s in question is when this will occur. The most recent model
guidance suggests that a wintry mix of sleet and freezing rain is
possible over the interior west mid Monday morning into Monday
afternoon before the full transition over to rain. With the most
recent guidance hitting this solution, I`ve tailored my forecast
grids to reflect this. Now, whether this solution stays or is
adjusted with future forecast packages remains to be seen...

Guidance keeps light to moderate rainfall across the area Monday
evening through Tuesday as the parent low lifts through the Upper
Mississippi Valley into western Lake Superior. A subtle shortwave
rotating around the low keeps the system rainfall going across our
area until Tuesday evening; once the parent low lifts into northern
Ontario Tuesday night, the cold front of the low is expected to move
through. Thus, expect any remaining light precip across our area to
transition back to snow Tuesday night into Wednesday from west to
east. Overall, guidance has around 1 to 2 inches of liquid falling
across our area from late Sunday through Tuesday. Hopefully, this
additional precipitation will reduce fire weather concerns as we
move towards summertime.

Behind the low, I`m thinking that we will see lake-effect snow
showers develop over the west snow belts as delta Ts get into the
upper teens. An additional shortwave looks to reinvigorate the lake-
effect snowfall Thursday before ridging moving in looks to kill it
Friday. We could see more precipitation as we move into next
weekend; however, it will depend on where a shortwave low moving
through the Plains tracks.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 117 AM EDT Sun Mar 24 2024

VFR conditions to prevail until early this afternoon. However, they
will quickly deteriorate to MVFR at that point when the next Plains
system moves closer to the Upper Peninsula.  Widespread MVFR
conditions will become predominant at all TAF sites with
visibilities dipping into the IFR range at times through Mon 05Z.
IFR will then become the prevailing flight category through the end
of the TAF period until the system weakens.  Meanwhile,
southeasterly winds will become strong at CMX this evening/tonight
with sustained speeds in the 12 to 15 kt range, gusting to 22 kts.

&&

.MARINE...
Issued at 357 PM EDT Sat Mar 23 2024

Light winds of 20 knots or less continue this afternoon into Sunday
morning before an approaching low pressure system progressively
increases winds from the east and southeast Sunday afternoon into
Monday; gales of 35 to 45 knots look to occur along the
International Border and over the western U.P. Monday into Monday
evening, with the highest winds being seen over the far western lake
near Minnesota. As the warm front of the low begins moving over the
lake Sunday night through Monday, we could see mixing decrease over
the lake and end the gales. However, if the warm air advection is
weak enough near the surface, we could see gales continue into
Tuesday, with the highest gales being seen near Whitefish Point.
Once the cold front moves through Tuesday night and Wednesday, we
could see westerly gales return across Lake Superior along and
behind it.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Storm Watch from this afternoon through Monday
     afternoon for MIZ001>003-009-010.

Lake Superior...
  Small Craft Advisory from 8 PM this evening to 8 AM EDT Monday
     for LSZ251.

  Gale Watch from Monday morning through Tuesday morning for
     LSZ162-243>245-251-263-264-266-267.

  Small Craft Advisory from 2 AM EDT /1 AM CDT/ Monday to 2 AM
     EDT /1 AM CDT/ Tuesday for LSZ240.

  Small Craft Advisory from 2 AM EDT /1 AM CDT/ to 8 PM EDT /7
    PM CDT/ Monday for LSZ241-242.

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

  Small Craft Advisory from 5 PM this afternoon to 8 AM EDT
     Monday for LSZ244-245.

  Small Craft Advisory from 5 PM this afternoon to 2 AM EDT
     Tuesday for LSZ246>248.

  Small Craft Advisory from 11 PM this evening to 2 AM EDT
     Tuesday for LSZ249-250.

Lake Michigan...
  Small Craft Advisory from 8 PM this evening to 8 AM EDT Monday
     for LMZ221-248-250.

&&

$$

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


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