Area Forecast Discussion
Issued by NWS Marquette, MI

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744
FXUS63 KMQT 111207
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
707 AM EST Wed Dec 11 2019

.SHORT TERM...(Today and tonight)
Issued at 438 AM EST WED DEC 11 2019

Across the Keweenaw, low-level water vapor and IR imagery this
morning, coupled with webcams and surface observations show moderate
to at times heavy snow continuing to impact locations around and
near the Houghton/Hancock area. Pre-dawn temperatures ranged from 15
below across parts of the interior west to near zero along the Lake
Superior shoreline. Winds have been rather slow to come up early
this morning, so wind chills are currently around the 15 to 20 below
zero mark across many locations. As the winds continue to increase
through the morning hours, wind chills are still expected to fall to
around 25 to 30 below inland from the Great Lakes and along the
eastern shoreline of the Bay of Green Bay. Wind chills are expected
to improve throughout the day, but given the lingering gusty
northwest to west winds, they look to only improve to around 5 to 15
below zero. So, still going to be a very brisk day!

Lake-effect snow showers currently in the west-southwest wind snow
belts early this morning will push into the northwest wind snow
belts through the early/mid morning hours. The strongest band over
the Keweenaw does look like it will be efficient enough to produce
another 3-4``, perhaps locally higher over the next couple of hours,
but as winds become northwesterly and the stronger area of
convergence funneling into the Keweenaw weakens, leaving behind
light to moderate snow showers through the rest of today. Given the
gusty winds and arctic airmass coming into the region, did maintain
SLRs around, but less than 20:1. So, not expecting the super fluffy
LES, but the combo of smaller snowflakes, blowing/falling snow will
allow for sharp visibilities restrictions at times. As the colder air
shifts east in time, it does looks like "warmer" 850mb air works
into the region and lift could move back down into the DGZ, which
would allow for some lingering fluffier snow this afternoon (albeit
less intense as inversion lower). Given the blowing snow and
expected reduced visibilities through at least mid-day, did opt to
to extend the advisory for Ontonagon and N. Houghton counties.

Multiple stronger bands pushing east across Lake Superior into
Canada this morning will drop southeast later this morning, bringing
impacts out east around the time for the morning commute and
lingering through this evening. The main areas impacted look to be
near and especially east of Munising and near/north of M-28, with a
sharp cutoff in snowfall totals expected. Much of western Alger
County and locations south of M-28 towards Lake Michigan look to
remain dry today. As the main area of ongoing snow over the lake
does push onshore in a couple of hours, models do show a few
stronger bands developing. With the arrival of the sharply colder
air this will help steepen inversion heights, but at times will push
the lift above the DGZ. However, time-height analysis in BUFKIT does
show some periods of times when stronger lift does look to dip into
the DGZ, so it`s not out of the question there could be a few
stronger, more efficient snow bands with higher SLRs. Regardless of
SLRs, visibilities will be a concern due to the falling and blowing
snow.

Elsewhere, lake-effect clouds and a few light snow showers may push
into the higher terrain of the north-central this morning and
afternoon, but very little in the way of accumulations are expected.
Much of central Upper Michigan, especially the south central will
see a cold, yet sunny day.

Tonight lingering lake-effect snow across the west-northwest wind
snow belts, which will eventually push offshore as flow backs
southwesterly ahead of a shortwave progged to lift northeast across
the region on Thursday. There could be some lingering impacts from
lake-effect snow, but it looks like a battle between better lift
through the DGZ, as 850mb temps warm slightly to around -15C,
lowering inversion heights. Opted to not extend any headlines into
the overnight hours due to the uncertainty as things start to wind
down in regards to the lake-effect snow. Otherwise, tonight mid-
level clouds moving in will help keep temperatures warmer.
Widespread snow starts to arrive from the southwest late tonight,
more details about that snow below in the long-term discussion.

.LONG TERM...(Thursday through Tuesday)
Issued at 512 AM EST WED DEC 11 2019

Models suggest that a nearly zonal pattern will become more
amplified into next week as a ridge builds along the west coast with
downstream troughing extends into the central CONUS from a deep low
over north central Canada. Several shortwave troughs will move
through the region bringing period pcpn chances as mainly seasonal
temps give way to cooling early next week.

Thursday, the models were in reasonable agreement with a shortwave
moving out of the northern Plains through WI that sill support a
period of moderate to strong 280k-290k isentropic lift across Upper
Michigan. The 2g-3g/Kg moisture available is consistent with QPF
values in the 0.20-0.35 range and overall snowfall amounts from 3 to
6 inches, heaviest south. SREF and GEFS plumes were also fairly
well clustered. SLR values are expected to drop from near 20/1 to
15/1 or less as the DGZ shrinks into the afternoon. As the deeper
moisture moves out during the evening, some fzdz may be possible
as low level moisture and isentropic lift lingers.

Friday, another shrtwv approaches with increasing pcpn chances
mainly over the west in the afternoon. With a continued shallow
moisture profile, any light pcpn that develops may be mixed with
fzdz.

Sat into Sun, there is less confidence with how the weak shrtwvs
will develop or interact and support light snow chances ahead of the
deepening trough. Eventually a n to nw low level flow will
strengthen between high pressure over the plains and a low moving
toward New England. This will support increasing LES chances as 850
mb temps drop from near -10C Sat to around -20C Sun.

Mon-Tue, the ECMWF and majority of GEFS ensembles keep the effects
from a developing storm mainly to the south and east of the northern
Great Lakes while the GFS brushes the area with some pcpn or lake
enhanced snow. So, for now, only lower end POPs remain with mainly
quiet weather. Temps should average slightly below normal with highs
in the upper teens and lower 20s.
&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 706 AM EST WED DEC 11 2019

Moderate to at times heavy lake-effect snow at KCMX continues to
bring IFR to LIFR vsbys, and MVFR ceilings this morning. Do expect
conditions to improve later this morning and afternoon, but
lingering snow and blowing snow will likely keep vsbys down in the
IFR range. Towards the evening hours, conditions should briefly
improve to MVFR, before trending back down to IFR as another push of
lake-effect snow lifts north across the Keweenaw Peninsula tonight.
Could catch a break in the lake-effect snow early Thursday morning,
but widespread snow moves back in around the tail end of this TAF
period.

KIWD will see gusty westerly winds today, with some MVFR lake-effect
clouds and a few showers moving over the next few hours. Otherwise,
conditions improve to VFR later this morning/afternoon and remain so
until late tonight/early Thursday morning when snow moves back in
with at MVFR ceilings to start. KSAW will see gusty northwest winds,
maybe a few lake-effect/diurnally driven clouds later this
morning/afternoon. Otherwise, mostly VFR conditions prevail until
snow arrives towards the end of this TAF period, when MVFR ceilings
and snow moves in.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 518 AM EST WED DEC 11 2019

Arctic air spilling through the region will bring northwest to west
winds to 40 kts over the eastern Lake this morning. With the cold
air and winds, heavy ice accumulation due to freezing spray will
be possible across the entire lake today. Additionally, some lake
effect snow showers will reduce visibilities today.

Winds will shift to southwest to south ahead of and during the next
shortwave moving through Thursday. These southern winds will be
light and help to warm things up to end the freezing spray concerns.
The more favorable conditions will linger into the early part of
the weekend. Another system will move through the region Saturday
and winds will swing around to the north Saturday afternoon into
the evening with winds of 20 to 30 knots. The colder air may help
produce some gale force gusts at bridge height, mainly over the
central lake and areas where freezing spray will be possible.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Wind Chill Advisory until noon EST /11 AM CST/ today for MIZ004-
     005-009>013-084.

  Winter Weather Advisory until 10 PM EST this evening for MIZ006-
     007-085.

  Wind Chill Advisory until 10 AM EST this morning for MIZ006-007-
     014-085.

  Winter Weather Advisory until 4 PM EST this afternoon for MIZ002-
     003.

  Winter Weather Advisory until 10 AM EST this morning for MIZ001.

Lake Superior...
  Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ this
     evening for LSZ162-240>244-263>267.

  Gale Warning until 5 PM EST this afternoon for LSZ264>267.

Lake Michigan...
None.
&&

$$

SHORT TERM...Ritzman
LONG TERM...JLB
AVIATION...Ritzman
MARINE...JLB



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