Area Forecast Discussion Issued by NWS Marquette, MI
000
FXUS63 KMQT 171743
AFDMQT
Area Forecast Discussion
National Weather Service Marquette MI
143 PM EDT Sun Mar 17 2024
.KEY MESSAGES...
- Lake enhanced/effect snow into Monday. The western U.P. near
Lake Superior, and Baraga, Alger, and northern Schoolcraft
counties could see an additional fluffy 2 to 5 inches.
- A prolonged gale event on Lake Superior is expected to end tonight.
- Blustery northwest to north winds continue today before
calming down tonight.
- The snow today into tonight, combined with blustery winds,
will result in some hazardous driving conditions.
- Light snow possible Tuesday followed by another lake effect
snow event through early Thursday.
- Blustery winds return Tuesday night and Wednesday.
- Northwest gale force winds and heavy freezing spray possible Tuesday
night and Wednesday across eastern Lake Superior.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 141 PM EDT Sun Mar 17 2024
Lake-enhanced snow showers continue across the northwest to north-
northwest snow belts the rest of this afternoon into tonight,
eventually becoming pure lake-effect late tonight as the better
moisture and troughing moves away. While the SLRs should be close to
around 20:1 due to temps being mostly in the DGZ, with the under-
performance of the snow totals over most of the western U.P. last
night, I`m cautious about how much more snowfall we will receive the
rest of today through tonight. That being said however, more recent
public reports seem to indicate that the snowfall rates are
beginning to increase to more in line to what we were thinking
yesterday. So, with that being said, it still looks like we will see
an additional 2 to 5 inches over Gogebic, Ontonagon, northern
Houghton, Baraga, and Alger/northern Schoolcraft counties from
2 PM EDT today to 8 AM EDT Monday morning. With blustery
conditions slowly winding down this evening, we still could see
some patches of blowing snow near the lakeshore this afternoon
and evening, which could cause some reductions in visibility
from time to time. With moderate to heavy snowfall being
reported every once in awhile across the different observation
sites near Lake Superior, I`m thinking these higher snowfall
rates will likely (70% chance) continue until late tonight.
Therefore, be on the lookout for slick roads and reduced
visibilities if you`re driving today and tonight near Lake
Superior; even the counties bordering Lake Superior that aren`t
currently under a Winter Weather Advisory could see these
hazards. Otherwise, besides the snowfall, temperatures have been
fairly static today. With cold air advection weakly continuing
over the area today into tonight, expect the static temperatures
today to slowly drop tonight once the sun goes down; expect
lows in the mid teens to mid-20s.
&&
.LONG TERM /TONIGHT THROUGH SATURDAY/...
Issued at 312 AM EDT Sun Mar 17 2024
Guidance packages continue to present a consistent representation of
the pattern for a majority of the extended forecast period. The
broad ridge extending up the west coast and downstream troughing
extending down the east coast will position Upper Michigan within
northwest flow early in the extended period, subjecting the forecast
area to the impacts of any clipper system riding the ridge southeast
into the trough. In terms of sensible weather, this means snow
chances, more winter like temperatures, and gusty winds. Toward the
end of the week, there`s a potential for the pattern to shift to
more zonal flow; however, confidence is low given the broad and
longitudinally elongated negative height anomaly stretching across
most of Canada and an eastward progressing deep trough into the west
coast. Overall, this results in less confidence in the forecast for
this weekend.
Tonight, Upper Michigan will continue to be under the influence of
mid-upper level cyclonic flow as a deep trough digs southeast into
the Ohio Valley. This will maintain the colder airmass aloft and
sustain the ongoing lake effect snow event for the forecast area.
Through the night, surface high and mid-level ridging will inch
across the Northern Plains. Given the timing of it`s progression
into the area though, suspect the snow shower activity downwind of
Lake Superior will persist into the early morning hours. However, by
sunrise, activity should begin waning as inversion heights fall due
to increasing subsidence and increasing mid-level dry air. By
afternoon, most, if not all show showers save for some isolated ones
in the east should be diminished. Guidance suggests additional
snowfall amounts on the order of 1 to 5 inches tonight into early
Monday morning for the northwest wind snow belts, with the higher
amounts being in Alger County and the Michigamme Highlands of
Baraga/Marquette counties.
Monday evening, a shortwave/clipper system will exit Canada into
northern Minnesota. As it moves into the Upper Great Lakes, light
snow will move in from northwest to southeast. Through the day on
Tuesday, a secondary surface low will slowly move eastward just
north of Lake Superior while a secondary shortwave drops into the
region. As this pulls away, a tighter pressure gradient will develop
over the region as cold air advection sweeps south. In effect, this
will develop lake effect snow showers and support blustery
conditions late Tuesday into Wednesday. An inverted surface trough
should gradually take form across eastern Lake Superior, sustaining
shower activity across eastern Upper Michigan into early Thursday.
High pressure shifts east through Ontario during the day Thursday,
working to diminish snow shower activity.
At this point, guidance begins to vary as the broad trough over the
east coast begins lifting while another closed low drops into
northern Manitoba, reinforcing the negative height anomaly across
Canada. Given the differences in timing and influence presented in
18 and 0z guidance, its unclear if a shortwave ejecting out of the
northern Rockies will get caught up in this broad circulation. If it
does, another round of precip could move into the region Thursday
night; if it doesn`t, then this impulse should remain too far south
to impact us. The same level of uncertainty exists for another wave
Friday night into Saturday.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 103 PM EDT Sun Mar 17 2024
Favorable lake-enhanced snowfall continues off of Lake Superior into
tonight over the northwest to north-northwest snow belts. That is,
until late tonight when the snowfall becomes pure lake-effect again
and dies out Monday morning. As this happens, expect KIWD and KCMX
to stay mainly IFR, with some bounces up and down to LIFR/airport
mins and MVFR from time to time this afternoon through tonight.
Meanwhile, KSAW will stay generally MVFR this afternoon. However,
there could be some degradation down to IFR vis if a heavier band
moves over the terminal. As the winds back more towards the north
tonight, conditions at KSAW worsen, becoming IFR. Once we get into
Monday morning, conditions are expected to improve to MVFR and
eventually VFR near the end of the TAF period for all the terminals.
&&
.MARINE...
Issued at 312 AM EDT Sun Mar 17 2024
A low end northwest gale event has been ongoing overnight, with
lightening winds observed across western Lake Superior. As we
progress through the night and Sunday, expecting the east half to
continue to see gales of 35-40kts. Winds should lighten by Monday
morning, with the lake being below 30kts near sunrise. Across the
west half, some stray gale force gusts will be possible, with
chances increasing as you move west toward Copper Harbor, but
otherwise.
Light winds should persist afterwards through Tuesday morning.
Another system moving through the region then will leave behind
another punch of colder air and tighter pressure gradient. There has
been a slight upward trend between previous and current guidance
packages, suggesting the threat for gales across the east half is
increasing. Additionally, with this trend and the colder airmass,
heavy freezing spray is appearing to be more likely. Winds decrease
Wednesday night, coming in at or below 20 knots the rest of the
week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 2 AM EDT /1 AM CDT/ Monday for
MIZ002>004-006-009-084-085.
Lake Superior...
Small Craft Advisory until 2 PM EDT /1 PM CDT/ Monday for
LSZ240>242.
Gale Warning until 2 AM EDT Monday for LSZ243>251-264>267.
Lake Michigan...
Small Craft Advisory until 11 AM EDT Monday for LMZ221-248-250.
&&
$$
SHORT TERM...TAP
LONG TERM...JTP
AVIATION...TAP
MARINE...JTP