Area Forecast Discussion
Issued by NWS Marquette, MI

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000
FXUS63 KMQT 262016
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
416 PM EDT Tue Mar 26 2024

.KEY MESSAGES...

- Scattered rain showers this afternoon change over to snow this
  evening with a cold front moving through.
- Rapidly falling temperatures behind the cold front tonight may lead
  to a flash freeze on untreated roadways.
- Westerly lake effect snow develops early Wednesday morning and
  continues through Thursday evening, mainly across the Copper
  Country.
- Several inches of snow and blowing snow expected, mainly
  across the Copper Country. Heaviest snow expected Wednesday
  afternoon and night. A Winter Weather Advisory has been issued
  for the Copper Country.
- 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 331 PM EDT Tue Mar 26 2024

Water vapor imagery and RAP analysis show a tight closed low moving
over western Lake Superior, amid broader midlevel troughing
extending across the Plains and into the Great Lakes. A pronounced
dry slot is evident across the UP and the eastern 2/3rds of Lake
Superior. At the surface, a 990mb surface low is analyzed over
western Upper Michigan, with a sharp cold front directed from
western Lake Superior to far western WI. Most of the area has been
able to enjoy a brief period of dry weather this afternoon, with Day
Cloud Phase showing lower cloud cover even mixing out across much of
the eastern half of the UP. Another embedded shortwave zipping
around the closed low is touching off another round of scattered
rain showers across north-central WI, which are moving into the
central UP already. Temperatures so far have stayed plenty warm
enough for precipitation to remain as all snow, with most of the
area hovering in the upper 40s.

This evening, the closed low will continue to move NNE over Lake
Superior, reaching Ontario closer to midnight. The frontal boundary
will soon begin tracking into the western UP, and should be through
most of the area by midnight. This should kick up another round of
light precipitation, with a quick transition over to snow. Given a
warm nose aloft in model soundings across the western UP, will not
rule out some pockets of freezing rain or ice pellets. A quick
transition over to a lake effect snow regime is expected the second
half of the night as 850mb temperatures quickly fall back to near -
12 to -15C. With winds generally out of the WSW, LES should be
confined to the far western UP, particularly the Keweenaw. Light
snow totals well below an inch are possible across much of the UP
with the passing cold front, with higher totals around an inch in
the WSW snow belts of the western UP.

Otherwise, with a rather tight pressure rise/fall couplet, and
robust CAA resulting in increasing lower level lapse rates (thus
allowing us to tap into stronger winds aloft), expect blustery
conditions to develop along and behind the cold front. Will note
that winds are already gusting up to 20-30mph in eastern MN, where
surface temperatures are already in the upper teens and lower 20s.
Temperatures likewise plummet with the passing front through the
first half of the night here in the UP. This is posing a concern for
a flash freeze tonight given wet roadways following the past day`s
precipitation. However, with most of the area having enjoyed a brief
dry period today, only a brief burst of light rain/snow this evening
with the passing front, and blustery conditions tonight potentially
helping to dry things out, this may not end up being particularly
widespread.

&&

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
Issued at 414 PM EDT Tue Mar 26 2024

Broad troughing mid-week will gradually shift to something more
zonal as the ongoing system lifts northeast and a deep closed low
drops south to near southern California. Together, this will support
a lake effect episode until ridging to shifts eastward across CONUS,
setting up a dry Friday before another eastward progressing system
moves into the midwest for the weekend.

Beginning Wednesday, cyclonic flow overhead in the wake of a
northeastward lifting surface low toward Hudson Bay and a closed low
pushing through Minnesota, combined with 850mb temps of -17 to
-15C will support lake effect snow for the western counties of Upper
Michigan. Inversion heights of around 4-5k ft should limit the
convective potential, but access to the DGZ should still support
widespread snow showers through the day. Model soundings show strong
winds within the mixed layer, upwards of 40 mph or so in the
Keweenaw Peninsula. These blustery winds will primarily be westerly
in the morning, but shift to southwesterly by afternoon, allowing
the best convergent signal to gradually lift and focus into northern
Houghton and Keweenaw County by Wednesday night. This northward
shift coincides with increasing cyclonic flow, which would further
increase snowfall rates. This matches well with the recent HREF >1
inch per hour rates, which lights up the Keweenaw with the greatest
potential beginning late Wednesday. Overnight Wednesday, winds
become more westerly, potentially enabling the more intense showers
to dip back into northern Houghton and Ontonagon counties. Between
Wednesday afternoon and Wednesday night, confidence is high (>75%)
that snow amounts will climb above 4 inches across the west wind
snow belts and medium (50%) that 8 inches will be exceeded. This,
with the wind potential and the likely blowing snow risk, opted to
issue a Winter Weather Advisory. Lake effect snow should gradually
taper off during the day Thursday.

Elsewhere in the southern and eastern portions of Upper Michigan
Wednesday into Thursday, mostly dry conditions with winds
potentially gusting upwards of 25 mph are expected. Daytime highs
Wednesday should top out in upper 20s to near 30F in the west and
low to mid 30s south and east. Overnight lows in the teens are
expected in the interior west. Elsewhere, near 20F lows are expected.

By Friday, surface high and mid-level ridging should support a dry
and seasonable day across the region. Daytime highs near 40F or in
the 40s are expected. As the pattern shifts to something more zonal,
a shortwave will press east across the Northern Tier as a weak
southern stream impulse shifts into the Illinois/southern Wisconsin
region. As the surface low pushes eastward into Lower Michigan and
eastern Great Lakes Saturday, inverted trough tied to the northern
stream shortwave will move through the Upper Great Lakes, giving us
a chance for another rain/snow mix Friday night and Saturday.

A quick look at next week is interesting. The trough setting up over
the western US will shift eastward, enabling a low to eject out of
the Central Plains while to the north, a northern stream shortwave
will drop southeast through the Northern Plains. Whether or not
these phase is the question, as their proximity to us could support
a moderate to heavy precip event if they do. 0 and 12z
deterministic present mixed options; these phase the two features
but vary greatly in where this occurs. No surprise, ensemble
clustering highlights this spread well in the location of the
surface low lifting out of the Plains. At this point, its advised
that anyone with travel plans Monday/Tuesday keep tabs on the
forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 123 PM EDT Tue Mar 26 2024

Poor flying conditions to persist for duration of TAF period with a
low pressure system moving northward across the UP this afternoon.
This is keeping in rain showers at IWD and CMX so far this
afternoon, though showers are becoming a little more spotty at SAW.
Otherwise, fog and low stratus are keeping in IFR or LIFR ceilings
at all terminals, as well as MVFR or worse visibility at times. A
cold front moving through tonight will help to lift ceilings to
MVFR/IFR, and bring in another quick round of precipitation
(changing to snow) the first half of the night. Lake effect snow
lingers after midnight, mainly at IWD and CMX, with a slight
improvement generally to MVFR at all terminals by the morning.
Meanwhile, surface winds shifting over to the WSW by tonight will
increase above the 12 kt threshold at all TAF sites with gusts up to
24 kts.

&&

.MARINE...
Issued at 459 AM EDT Tue Mar 26 2024

Lake Superior will remain under the influence of low pres that will
track from ne IA early today across western Lake Superior this
aftn/early evening. Result will be changing wind directions and wind
speeds across the lake. Ongoing ne gales of 35-40kt across western
Lake Superior will temporarily subside in the vcnty of the passing
low this aftn. Over eastern Lake Superior, se winds will
occasionally gust to 35kt gales this morning closer to the
International Border. As the low lifts n of the area this evening, w
to wsw winds will ramp up to 35-40kt gales over much of w and
central Lake Superior. These gale force winds will continue thru Wed
before diminishing by late Wed evening. Internal probabilistic
guidance indicates a 25-35pct chc of gusts into the 40-45kt range in
a large area surrounding the Keweenaw Peninsula. Freezing spray will
also occur during these gales, and some hvy freezing spray will
occur at times over portions of western Lake Superior late
tonight/Wed morning. Westerly winds of 25-30kt will then prevail
across Lake Superior late Wed night thru Thu. A high pres ridge will
then arrive on Fri, leading to winds diminishing to mostly under
20kt. Wind should remain mostly under 20kt into and thru the
upcoming weekend.

&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 2 PM Wednesday to 8 AM EDT
     Thursday for MIZ001>003.

Lake Superior...
  Small Craft Advisory until 8 AM EDT /7 AM CDT/ Wednesday for
     LSZ240-249>251.

  Gale Warning until 11 PM EDT /10 PM CDT/ Wednesday for LSZ162-
     244-263-264.

  Heavy Freezing Spray Warning from 5 AM EDT /4 AM CDT/ to 2 PM
     EDT /1 PM CDT/ Wednesday for LSZ162-240>244-263-264.

  Small Craft Advisory until 8 PM EDT /7 PM CDT/ this evening
     for LSZ241>243.

  Gale Warning from 8 PM EDT /7 PM CDT/ this evening to 11 PM
     EDT /10 PM CDT/ Wednesday for LSZ241>243.

  Small Craft Advisory until midnight EDT tonight for LSZ245>248.

  Gale Warning from midnight tonight to 5 PM EDT Wednesday for
     LSZ245>248-265.

  Gale Warning from midnight tonight to 11 PM EDT Wednesday for
     LSZ266.

Lake Michigan...
  Small Craft Advisory until 8 AM EDT Wednesday for LMZ221-248-
     250.

&&

$$

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


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