Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 250841
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
341 AM EST Sun Feb 25 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...(Monday through Saturday)
Issued at 338 AM EST SUN FEB 25 2018

The recent active weather pattern will take a break through mid
week. With westerly flow aloft there will be no real intrusions of
cold air as more mild pacific origin airmass dominates. Even with
the fresh snow in place, with good deal of sunshine expected both
Mon and Tue, could see highs make run well into the 40s.

Low pressure crosses northern Ontario on Tue. Weak cold front tied
to low slides across Upper Michigan Tue night and may provide focus
for some light rain and snow showers over the south central Tue
night. High pressure brings another dry day on Wed but more of a
north to northeast wind will keep it cooler than earlier in the
week.

Only real potential for significant weather the upcoming week is Wed
night into Thu as upper trough tries to deepen across the Great
Lakes. Associated sfc trough and low pressure should bring a period
of moderate to heavy qpf WI into lower MI, especially Thu. ECMWF
keeps main focus for rain and snow south of Upper Michigan while GFS
clips southern area with at least light rain/snow. GFS ensembles
(GEFS) indicate highest probs for 0.50-1.00 inch of qpf stays south
but there is still room for light snow to make it into at least
southern forecast area. Projections for this system continue to
show a sharp north to south gradient in precip. Will keep chance
pops attm for scntrl and southeast area on Thu. Once that system
moves by, high pressure brings more dry weather with seasonable
temps into the weekend.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1154 PM EST SAT FEB 24 2018

As a low pres system rapidly lifts ne across Upper MI
overnight/early this morning, a band of mdt/hvy snow will swing
across the area, impacting all terminals with at least a 2-4hr
period of LIFR conditions. The potential is there for snow to mix
with sleet and/or freezing rain at times at KSAW, but confidence
remains too low to include a mention of this wintry mix in the fcst.
Snow will rapidly diminish/end early this morning with conditions
improving to MVFR. Strong and gusty westerly winds are then expected
today as the low lifts n of the area, especially at KCMX where gusts
up to around 45kt are likely. Gusts to around 35kt should occur at
KIWD/KSAW. With the snow expected to be wet and heavy, confidence in
blsn is low, but would be most likely to occur at KCMX. Conditions
will improve to VFR at all terminals by evening, if not sooner.
&&

.MARINE...(For the 4 AM Lake Superior forecast issuance)
Issued at 338 AM EST SUN FEB 25 2018

As a strengthening low pressure system tracks across Lake Superior
this morning, expect southeasterly gales of 40 to 45 knots across
the far eastern portions of the lake. As the surface low lifts
northeast of the region later this morning, westerly gales to 45
knots will develop over much of Lake Superior. Some gusts may reach
storm force, but not prolonged enough to issue storm warning. Expect
the gales to linger through tonight. 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 until 7 AM EST /6 AM CST/ this morning
     for MIZ004-005-010>013-084.

  Wind Advisory from 7 AM this morning to 7 PM EST this evening
     for MIZ001>005-084.

  Winter Weather Advisory until 10 AM EST this morning for MIZ006-
     007-014-085.

  Winter Storm Warning until 10 AM EST this morning for MIZ001-003.

  Winter Storm Warning until 7 AM EST /6 AM CST/ this morning for
     MIZ002-009.

Lake Superior...
  Gale Warning until 1 AM EST Monday for LSZ266-267.

  Gale Warning from 9 AM EST /8 AM CST/ this morning to 10 PM EST
     /9 PM CST/ this evening for LSZ162-263>265.

Lake Michigan...
  Gale Warning from 7 AM this morning to 7 PM EST this evening for
     LMZ248-250.

&&

$$

SHORT TERM...Ritzman
LONG TERM...JLA
AVIATION...Rolfson
MARINE...JLA



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