Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 141959

Area Forecast Discussion
National Weather Service Marquette MI
259 PM EST Sun Jan 14 2018

.SHORT TERM...(This evening through Monday)
Issued at 259 PM EST SUN JAN 14 2018

...Moderate to heavy lake effect/enhanced snowfall expected tonight
downwind of Lake Michigan...

Upstream of Upper Michigan, water vapor imagery showed shortwave
energy digging south across the northern Plains this afternoon with
its associated low pressure trough tracking just ahead across the
Upper Mississippi Valley. As a sharp axis of 850mb warm air
advection continued to nose into the surface through this afternoon,
widespread snow developed across the northern Plains and stretched
into northern portions of Minnesota. Immediately downstream of the
area, a band of lake effect snow has developed across eastern Lake
Michigan. Elsewhere, conditions were mostly sunny across Upper
Michigan this afternoon with mid and high clouds beginning to stream
eastward. The main forecast concerns during this time period are
widespread light system snow tonight through Monday, moderate to
heavy lake enhanced snow expected off of Lake Michigan tonight into
Monday, and then the return of lake effect/enhanced snow across the
far west and north central on Monday.

Widespread system snow tonight through Monday transitioning to lake
enhanced snow on Monday: As the above mentioned shortwave continues
to dig south across north central portions of the CONUS, widespread
snow will move across much of Upper Michigan. The stronger warm air
advection and moisture is expected to remain south of the area;
therefore, system snow over the next 24 hours is expected to remain
fairly light. As the shortwave becomes cutoff across the region
tonight into Monday and slows down, weak warm air advection will
continue to linger across the area allowing the widespread light snow
to linger. Overall, the system snow should only amount to around 1
to 3 inches across the area, except downwind of Lake Michigan where
lake enhanced snow is expected (see the below discussion). As the
surface low slowly tracks across southern Lake Michigan into Lower
Michigan, flow will back east-northeast on Monday, so expect lake
enhanced snow to impact the Keweenaw and north central portions of
Upper Michigan. Models are not highlighting much QPF across these
areas, outside of the high-res ARW/NMM, likely due to the lack of
saturation through the DGZ advertised by forecast soundings. If the
airmass can modify more than what is shown in current guidance,
headlines may be needed across the Keweenaw Monday. Further west,
medium and high-res guidance have slowed the arrival of lake effect
snow on the back side of the exiting surface trough, with the
potential for meso-lows coming onshore shifting a bit further west
across far northwest Wisconsin.

Moderate to heavy lake enhanced snow downwind of Lake Michigan
tonight into Monday: The main concern during this time period is the
band of moderate to heavy lake effect/enhanced snow expected to push
onshore tonight through mid/late Monday morning downwind of Lake
Michigan and its impacts on travel. With the surface low progged to
track across Wisconsin/Iowa/Illinois, southwesterly flow across
northern Lake Michigan will back southeasterly and allow this strong
band of lake effect snow to push onshore across Schoolcraft and
Delta counties late tonight into Monday morning, and become enhanced
by lingering synoptic-scale lift. With 850mb temperatures around -15
to -18C initially and the leading edge of the PV anomaly tracking
across the region, inversion heights will lift upwards of 8-10kft,
with decent lake induced instability. Therefore, expect a deep
convective layer in which forecast soundings continue to show strong
lift and saturation through the DGZ. This will result in SLRs of at
least 20-30:1. Initially as this band comes onshore, the 1000-850mb
convergence signature remains fairly transient across Schoolcraft
county, but based on the strong lift through the DGZ, wouldn`t be
surprised if locations across southern portions of the area pick up
a quick 4 to 6 inches of snow as the band moves overhead. It is
conceivable that a few locations across far southwest Schoolcraft
county may see warning criteria snowfall, but based on how transient
the band is expected to be opted to hold off on upgrading their
advisory for now.

As winds continue to back Monday morning expect the strong band of
lake enhanced snow to push into Delta, Menominee, and possibly
portions of Dickinson Counties. This will result in slippery to
difficult travel Monday morning, including along US-2 and US-41.
Delta County looks like it will take the brunt of the accumulating
snow, especially the Garden and Stonington Peninsulas where the lake
effect snow is expected to be more persistent. By the end of Monday,
far southeast portions of Delta County may see upwards of 10 to 12
inches of new snow. Elsewhere, across Delta County, 6 to 8 inches
are expected with much of this snow falling from the early to late
morning hours on Monday. Confidence is not as high in regards to how
things will play out across Menominee and Dickinson Counties as the
low-level moisture gets reduced significantly due to ice cover on
the Bay of Green Bay. However, there should still be enough
lingering modified moisture and lift to foster an additional 2 to 4
inches Monday morning west of the Bay of Green Bay. Therefore, did
opt to expand the winter weather advisory further west to include
Dickinson and Menominee Counties to draw attention for potential for
travel impacts during the Monday morning commute.

.LONG TERM...(Monday through Saturday)
Issued at 515 AM EST SUN JAN 14 2018

Attention is on Mon into Tue when moderate to potentially heavy lake
enhanced snow is expected.

An upper closed low accompanied by a more broad surface low will
move S of the area Sun night and Mon, then shift E Mon night. Lake
enhancements with southerly winds will favor S-central Upper MI for
snow Mainly Mon morning, potentially with another 1-3 inches of
accumulation there. Elsewhere, light synoptic forced snow is
expected Mon, except potentially over the far W where heavier lake
enhanced snow is possible depending on meso-low development and
placement. If better banding can get into the Ironwood area, some
significant snowfall amounts could result, but at this time it is
too uncertain to put that into the forecast.

For Mon night into Tue, as the low shifts E, meso-lows will not be
as much of an issue and the typical NE-N wind snow belts will see
moderate to potentially heavy snow. Generally have 6-8" Mon night
through Tue over western Ontonagon and Gogebic Counties, the higher
terrain near Lake Superior in Marquette County and a small portion
of the keweenaw, with lower amounts elsewhere. However, if winds
shift faster, these amounts could be higher.

No significant impacts expected after Tue. Will see a warmup with
highs around freezing Thu through the weekend.

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1247 PM EST SUN JAN 14 2018

MVFR ceilings will quickly move west to east across Upper MI this
afternoon into this evening, followed shortly after by IFR
visibilities, as a trough brings -SN to the area. There could be a
period of LIFR visibilities at KIWD this evening. Also, LIFR
visibilities will be possible at KCMX late this evening into Monday
morning due to lake enhancement from Lake Superior, but confidence
was too low to include a specific time in the TAF at this point.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 259 PM EST SUN JAN 14 2018

As low pressure tracks south of the area across Wisconsin and
Illinois tonight, an inverted surface trough will linger across Lake
Superior and bring winds of 20 to 30 knots. Cannot rule out a few
gale force gusts to 35 knots tonight out ahead of the low pressure
system across the eastern half and then again Monday night night
behind the exiting low across the west half. Periodic heavy
freezing spray is possible behind the exiting system, otherwise only
moderate freezing spray is expected through the first half of the
week. Tuesday through the end of the week, expect winds to remain
between 20 to 30 knots with a chance for gales Wednesday.

Upper Michigan...
  Winter Weather Advisory until 1 PM EST Monday for MIZ014.

  Winter Weather Advisory from 7 PM this evening to 1 PM EST
     Monday for MIZ085.

  Winter Weather Advisory from midnight tonight to 6 PM CST Monday
     for MIZ011-012.

  Winter Storm Warning from 1 AM to 7 PM EST Monday for MIZ013.

Lake Superior...
Lake Michigan...


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