Area Forecast Discussion
Issued by NWS Marquette, MI

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210
FXUS63 KMQT 242050
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
350 PM EST Sat Feb 24 2018

.SHORT TERM...(This evening through Sunday)
Issued at 348 PM EST SAT FEB 24 2018

...Winter storm expected tonight into Sunday followed by strong
and gusty westerly winds...

The main forecast concerns over the next 24 hours are the arrival of
a winter storm tonight through early/mid Sunday morning and it`s
impacts, followed immediately by the onset of strong and gusty
westerly winds behind the exiting system. Overall did not make many
changes to the inherited forecast with the highest snowfall totals
still expected across the far west, with 5 to 7 inches of snow
expected, and will tapper off as we move towards eastern Upper
Michigan where 1 to 3 inches are possible as snow may mix with
freezing rain and sleet at times. Did opt to add a few more counties
to the inherited wind advisory for Sunday, mainly for the far west
and north central.

Tonight, the shortwave currently ejecting out of the central and
southern Rockies will lift northeast across the Plains and up into
the Upper Mississippi and Great Lakes Region. Given the track of
this shortwave and its progged negative tilt, models have come into
good agreement with the track of the surface low remaining across
western and central Upper Michigan, before lifting northeast over
north central Lake Superior. The initial surge of wintry
precipitation tonight will arise as warm air advection and moisture
transport from the south-southeast strengthen. As the main shortwave
pivots across the Upper Great Lakes early Sunday morning, the
arrival of the main upper-level PV anomaly/vort maximum will work in
concern with the strengthening upper-level jet to provide addition
lift to prolong this winter weather event through the early/mid
morning hours on Sunday.

Across the west and north central, precipitation should remain all
snow during this event. With thermodynamic profiles well below the
DGZ and warmer than -10C have lowered SLRs down a bit, so still
expecting this round of system snow to take on wet and heavy
characteristics, making snow removal more difficult. Across the
east, confidence is not high in regards to how precipitation types
will play out as there are still some pretty large discrepancies in
regards to the magnitude of the return flow. Complicating matters
further, as this better lift and stronger warm air advection
arrives, temperatures at the surface will also warm towards and/or
above freezing. Therefore, we`re still looking at a wintry mix of
snow, freezing rain, and sleet across the east, but if the warmer
air and deeper moisture can return this far north we could see ice
accumulations greater than what is reflected within this forecast
update. Across the south central, precipitation will fall as a mix
of rain and snow at times, with a small window for some freezing
rain.

During the early to mid morning hours on Sunday, lingering wintry
precipitation will begin to diminish from the southwest to
northeast, with perhaps a few light snow showers possible in the
west wind belts throughout the day; however, the focus then quickly
shifts towards the onset of strong and gusty westerly winds. Behind
the exiting system, winds aloft will remain strong with around 40 to
50 knots just above the surface. Therefore, with cold air advection
giving way to steeper low-level lapse rates and stronger turbulent
mixing, would not be surprised if we see wind gusts approach and/or
exceed 45 knots in some locations. The 4-6mb/3 hour pressure rises
behind the system will certainly assist in these gustier winds as
well. Given the westerly wind direction, the strongest winds should
be felt across the Keweenaw Peninsula, and then further south into
Ontonagon county and across the north central, especially near Lake
Superior and across the higher terrain.

.LONG TERM...(Sunday night through Saturday)
Issued at 308 PM EST SAT FEB 24 2018

Pretty tranquil, even early spring-like, stretch of weather expected
through the early part of the extended forecast.  With mean trough
position over the western U.S. and west southwesterly flow into the
Great Lakes temperatures will remain above normal for much of the
week. Temperatures will climb into at least the lower 40s inland
from the ice covered nearshore areas of the Lakes through Wednesday.
If any of those days end up being full sun days...temperatures could
go even higher.

The only time period for any impactful weather this week will occur
late Wednesday night through Thursday.  Models are still having some
consistency issues with the handling of energy ejecting out of the
trough in the southwest but they are suggesting an upper low closing
off somewhere over the upper midwest or lower Great Lakes with an
associated surface low moving eastward through these areas. How far
north and west the precipitation shield gets will be the forecast
challenge over the next couple of days. There will be plenty of
moisture for the system to work with but if the track stays over the
southern Lakes any significant precipitation would be confined to
the southern U.P. or further south. Precipitation type would also be
an issue with not much cold air wrapped into the system.

Upper ridging will build back into the Great Lakes by late in the
week into next weekend with temperatures continuing to run at or
above normal.
&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1233 PM EST SAT FEB 24 2018

There is a narrow area of scattered to broken MVFR ceilings just
south of KSAW this afternoon, but do not expect much of an impact
from these clouds as they continue to thin. Otherwise, VFR
conditions will persist across all terminals through the remainder
of this afternoon. However, as we progress through the overnight
hours conditions will deteriorate rapidly as moderate to heavy wet
snow is expected to impact all terminals as a surface low tracks
northward across the region. Expect visibilities to be sharply
reduced for at least a 3-6 hour time period as this band of snow
pushes northward. The potential is there for snow to mix with sleet
and/or freezing rain at times at KSAW, but confidence was not high
enough to include mentions of this wintry mix at this time.

While ceilings and visibilities will improve by mid-Sunday morning,
strong and very gusty westerly winds, especially at KCMX, will pick
up behind the exiting surface low. With the snow expected to be wet
and heavy, confidence is not high if we will see blowing snow and
resulting reduced visibilities on Sunday.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 348 PM EST SAT FEB 24 2018

As a strengthening low pressure system tracks across Lake Superior
later tonight/Sunday morning, southeasterly winds will ramp up to
gales of 40 to 45 knots across the far eastern portions of the lake.
As the surface low lifts northeast of the region through Sunday
morning, westerly gales will wrap around the exiting surface low.
Expect winds to reach high-end gales and perhaps even a few gusts
that approach storm force. Expect these gales to linger through
Sunday night. Monday through the middle of next week, winds will
start off between 20 and 30 knots, but they will gradually weaken to
less than 15 knots by Wednesday.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 11 PM EST /10 PM CST/ this evening
     to 7 AM EST /6 AM CST/ Sunday for MIZ004-005-010>013-084.

  Wind Advisory from 7 AM to 7 PM EST Sunday for MIZ001>005-084.

  Winter Weather Advisory from 1 AM to 10 AM EST Sunday for MIZ006-
     007-014-085.

  Winter Storm Warning from midnight tonight to 10 AM EST Sunday
     for MIZ001-003.

  Winter Storm Warning from 10 PM EST /9 PM CST/ this evening to 7
     AM EST /6 AM CST/ Sunday for MIZ002-009.

Lake Superior...
  Gale Warning from 1 AM Sunday to 1 AM EST Monday for LSZ266-267.

  Gale Warning from 9 AM EST /8 AM CST/ Sunday to 1 AM EST
     /midnight CST/ Monday for LSZ162-263>265.

Lake Michigan...
  Gale Warning from 7 AM to 7 PM EST Sunday for LMZ248-250.

&&

$$

SHORT TERM...Ritzman
LONG TERM...MZ
AVIATION...Ritzman
MARINE...Ritzman



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