Area Forecast Discussion
Issued by NWS Marquette, MI

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234
FXUS63 KMQT 222026
AFDMQT

Area Forecast Discussion
National Weather Service Marquette MI
326 PM EST Fri Feb 22 2019

.SHORT TERM...(This evening through Saturday)
Issued at 324 PM EST FRI FEB 22 2019

Surface ridge axis passes overhead this evening through the wee
hours of Saturday morning. As winds go nearly calm, have dropped
lows into the mid teens over the east. Did not go too low, however,
because WAA clouds aloft will inhibit radiative cooling.

For the day Saturday, looking at a mid-level shortwave in SW flow
passing through Wisconsin and clipping Upper Michigan. Will see a
broad region of WAA/isentropic lift out ahead of the wave, but in
addition, meso models show an fgen band around 700 mb lifting
across central and western Upper Michigan late morning through the
afternoon Saturday. This could lead to enhanced snowfall in these
areas. So for precip, leaned towards hi-res models as there is a
solid consensus in them for a broad band of QPF exceeding 0.3" and
perhaps a narrower band embedded in there with QPF in excess of
0.5". While all of the U.P. will see at least light accumulations,
this heavier band is most likely to set up along a SW to NE axis
through Iron, Baraga, and Marquette Counties, and perhaps northern
Dickinson.

The DGZ will be pretty high (around 600-700 mb and above) and pretty
thin (only about 100 mb thick) which, along with fairly strong winds
below the dendritic growth layer shattering the dendrites, will
probably lead to smaller flakes and therefore lower SLRs of around
10-12:1. Still, given the QPF, this results in 3-5" of snow for the
aforementioned heavier snow areas and generally 1-3" elsewhere.
Since this predominantly falls in less than 12 hours and since it
will be a wetter snow, have opted to hoist a Winter Weather Advisory
for Saturday ahead of the main event even though snow amounts are a
bit on the marginal side.

There are two close calls here: Iron Mountain is tough as most hi-
res guidance keeps them right on the edge of the heavier snow to
their west. So is the Keweenaw as the ARW and extended HRRR put the
band over them, so we`ll need to watch things closely to see if a
small shift in snow placement drastically changes snow totals in
either of these places.

For temps on Saturday, also tended towards the hi-res models on
land. Did this assuming that they`re probably handling evaporative
cooling under the heavier snow better than the coarser global models.

Big system moves in very late in the period and will be covered in
the long-term section.

.LONG TERM...(Saturday through Thursday)
Issued at 507 AM EST FRI FEB 22 2019

...SIGNIFICANT WINTER STORM TO IMPACT THE REGION STARTING SATURDAY
NIGHT...

Most attention is on Sat night into Mon, but isentropic ascent ahead
of the upcoming system looks to bring snow and a wintry mix on Sat.
Generally expecting 0.1-0.2 inches of QPF through the day, which is
supported by most guidance. The NAM is by far the outlier with 0.5-
0.75 inches, but it is the outlier with the upcoming system and was
not used as input into this forecast. Expect 1-2 inches of snow on
Sat with some trace ice amounts possible over the S.

Very strong, dynamic system moves in Sat night and Sun. Model
guidance is in relatively very good agreement with excellent
consistency, with the exception of the NAM which was not used for
this forecast. A stacked low will move from NW MO at 00Z Sun to E-
central Upper MI by 12Z Sun while the surface low deepens to below
979mb! The low keeps a quick pace and moves to Quebec by 00Z Mon.
Models have been very persistent with placement and amounts of
precip and the strength of the system, which allowed enough
confidence for a watch issuance this morning, which was also
supported by the very impactful nature of the system. Main hazards
are very heavy snowfall (especially over the NW half), a
snow/sleet/freezing rain combo SE, and strong winds (especially near
Lake Superior). Precip moves in from the S a little after 00Z Sun
and largely exits by 18Z with just some lingering snow and lake
effect remaining. Current forecast has 10+ inches of snow over the
NW half, much of which falls between 06Z and 18Z Sun. Snow will be
wet and heavy. Over the SE, 3-6 inches of snow is expected along
with sleet and freezing rain accumulations, which are less certain.
Winds increase dramatically on Sun when the system bombs out and
starts to shift quickly E. Currently forecasting NW gusts to 55mph
over and near central Lake Superior, with gusts of 35-45mph
elsewhere. This seems very reasonable, but could end up even higher.
Blowing snow and some power outages will be the primary impact from
the wind. Blowing snow near Lake Superior E and Harvey could lead to
impossible travel Sun into early Mon. Only expecting relatively
minor track/amount changes to the forecast. The trickiest part of
this forecast is ptype forecasting over the SE half, but that is
typical with this type of setup.
&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1242 PM EST FRI FEB 22 2019

Clear skies and thus VFR at SAW and IWD through the rest of this
afternoon, though MVFR cig is holding on at CMX. Conditions
deteriorate late tonight at all three sites with the arrival of
snow. Have kept MVFR cig and IFR vis at all three sites through the
end of the TAF period for now but it is possible that the snow is
periodically heavy enough to reduce vis to LIFR, mainly Saturday
afternoon. Also a slight chance of LLWS mid-late morning Saturday
but looks pretty marginal and being late in the TAF period have left
it out for now.
&&

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 324 PM EST FRI FEB 22 2019

Quiet through Saturday night with winds less than 25 knots.
Northerly gales expected Sunday morning across Lake Superior,
building to storms to 50 knots over the eastern arm Sunday afternoon
and night. Gales subside over the western arm Sunday night and over
the eastern arm midday Monday. After that, quiet conditions expected
through the middle of next week with gusts less than 20 knots over
the western arm and less than 25 knots over the eastern arm.
&&

.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
  Winter Weather Advisory from 7 AM EST /6 AM CST/ to 7 PM EST /6
     PM CST/ Saturday for MIZ001>005-009>011-084.

  Winter Storm Watch from Saturday evening through late Sunday
     night for MIZ001>005-009-084.

  Winter Storm Watch from Saturday evening through Monday
     afternoon for MIZ006-007-085.

  Winter Storm Watch from Saturday evening through Sunday evening
     for MIZ010>014.

Lake Superior...
  Storm Warning from 10 AM Sunday to 4 AM EST Monday for
     LSZ249>251-266-267.

  Gale Warning from 7 AM EST /6 AM CST/ Sunday to 1 AM EST
     /midnight CST/ Monday for LSZ162-240>248-263>265.

Lake Michigan...
None.
&&

$$

SHORT TERM...RJC
LONG TERM...Titus
AVIATION...RJC
MARINE...RJC



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