Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 120509

Area Forecast Discussion
National Weather Service Marquette MI
1209 AM EST Thu Jan 12 2017

.SHORT TERM...(This evening through Thursday)
Issued at 346 PM EST WED JAN 11 2017

Very busy shift dealing with the snow that has been largely driven
by FGEN. Heaviest band ended up settling over central Marquette
through western Iron Counties, dropping somewhere around 4-6 inches.
That snow is diminishing and moving E, and will exit the area this
evening. See the WSW for more details on exiting snowfall.

NW winds tonight will swing around to the SW late tonight ahead of
the next disturbance. Even with 850mb temps around -20C, only
expecting light scattered LES tonight due to very dry low level air,
low inversion heights, and anticyclonic flow. LES may pick up later
in the day tomorrow over the Keweenaw as the disturbance moves in
and flow turns out of the WNW late.

.LONG TERM...(Thursday night through Wednesday)
Issued at 347 PM EST WED JAN 11 2017

The medium/extended range period wl start on the cold side as an
arctic airmass surges into the Upr Lks on Thu ngt behind a shrtwv
tracking thru scentral Canada. But as upr hgts begin to rise as the
arctic branch lifts to the n in Canada and an upr rdg builds over
the se CONUS, there wl be a gradual warming trend into next week.
Sfc hi pres that wl dominate the Great Lks during this transition wl
bring mainly dry wx into at least Mon. Depending on the track of a
polar branch shrtwv/sfc lo pres lifting ne fm the srn Plains on the
nw flank of the se upr rdg, there could be a mixed rain/snow event
next Tue into Wed. Pacific air and well above normal temps wl
dominate much of next week.

Thu ngt/Fri...Thu evng wl feature strong wnw winds under the tight
pres gradient in the wake of Thu cold fropa. H925 winds fcst as hi
as 40kts early in the evng in area of strong caa/enhanced mixing and
ahead of pres rise center aprchg fm MN that allows the isallobaric
wind to line up with the gradient flow wl result in wind gusts that
at least aprch advy criteria. With the influx of arctic air in its
wake that wl drop h85 temps as lo as about -25C, les and blsn wl
return in the favored sn belts downwind of Lk Sup. But vigorous
subsidence under strong dnva/deep lyr qvector dvgc in the wake of
passing shrtwv into Quebec that wl drop the invrn base to near 3k ft
agl and the near absence of a dgz in the arctic air invasion wl tend
to limit the les intensity. The best chc for moderate sn totals wl
be over the e, where there wl be a longer fetch acrs Lk Sup and more
moistening/temp moderation that allows a 2k ft deep dgz just above
the sfc. Even though no heavy les is likely, the smaller flakes/
gusty winds/blsn wl efficiently reduce vsby in the favored sn belts.
Some marginal wind/les/blsn advys wl probably be needed in these
exposed wnw sn belts. The magnitude of the blsn wl diminish later on
Thu ngt as the pres gradient and winds slowly slacken following the
passage of the pres rise center to the e. Since min temps over the w
near the WI border wl be dominated by a more unmodified flow of
arctic air, min temps are likely to fall to arnd -10F. These areas
away fm lk moderation wl see wind chills aprch advy criteria even
though the pres gradient/winds wl slacken during the ngt. The
arrival of the trailing sfc hi pres rdg/more acyc and weakening llvl
winds wl bring improvement on Fri even though some light les wl
linger as h85 temps moderate slowly toward -15C late in the day
under continued larger scale subsidence. With a wshft to the sw,
locations over the w except for the Keweenaw should see an end to
the les during the aftn.

Fri ngt/Sat...Hi pres is fcst to build into the central Great Lks to
the s of an arctic branch shrtwv passing thru nw Ontario. Some clds
and perhaps a few sn showers wl brush the nrn tier as the lo pres
trof associated with this feature swings across Lk Sup. But with
pwat fcst as lo as 0.10-0.15 inch and an absence of mstr inflow, any
pcpn wl be light and limited to areas near Lk Sup. Depending on the
cld cover, some locations over the scentral could be quite chilly on
Fri ngt with lighter winds closer to the hi pres passing just to the
s. More clds and a stronger wsw flow over the nrn tier wl limit the
diurnal temp fall in that area. As h85 temps warm to arnd -8C on
Sat, expect max temps to rebound into the 20s.

Sat ngt into Mon...Hi pres is fcst to build over the Upper Lks and
bring dry wx to the cwa under rising upr hgts as the arctic branch
flow retreats into Canada and an upr rdg builds over the se CONUS.
There wl be a slow warming trend as h85 temps recover to arnd 0C on
Mon. Tended to lower fcst min temps a bit blo the consensus on Sat
ngt with light winds and moclr skies.

Tue/Wed...While there are still some differences in the longer range
fcsts, many of the models have trended toward allowing a polar
branch shrtwv lifting out of the srn Plains under the sw flow arnd
the se CONUS upr rdg to push far enuf n to bring some pcpn to Upr
MI. Since most of the guidance shows h85 temps rising aoa 0C, any
pcpn wl be at least mixed with rain and freezing rain.

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1209 AM EST THU JAN 12 2017

MVFR cigs with lake effect clouds and a few light snow showers are
expected to persist overnight until winds back to the southwest
THursday morning. Although conditions will improve to VFR the
southwest winds will become gusty, especially at CMX where some
gusts to around 35 knots are possible which result in blsn with vsby
likely into the MVFR category.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 347 PM EST WED JAN 11 2017

Winds will diminish under 20 kts tonight as a hi pres ridge builds
into the Upper Lakes. A strong cold front will push across Lake
Superior on Thu, followed by wnw gales to 40-45 kts and heavy
freezing spray as the strong winds whip up hier waves in the presence
of an incoming arctic airmass. Opted to issue gale/heavy freezing
spray warnings for much of Lake Superior. Expect the gales/heavy
freezing spray to slowly diminish late Thu night as hi pres builds
over the Upper Lks on Fri. The relatively weak pres gradient around
this hi pres will cause winds to run no hier than about 25 kts thru
the weekend into Mon.

Upper Michigan...
Lake Superior...
  Heavy Freezing Spray Warning from 7 PM this evening to 11 AM EST
     Friday for LSZ251-267.

  Gale Warning from 4 PM this afternoon to 1 AM EST Friday for

  Heavy Freezing Spray Warning from 3 PM this afternoon to 11 AM
     EST Friday for LSZ248>250-266.

  Heavy Freezing Spray Warning from 11 AM EST /10 AM CST/ this
     morning to 11 PM EST /10 PM CST/ this evening for LSZ162.

  Gale Warning from 1 PM EST /noon CST/ this afternoon to 10 PM
     EST /9 PM CST/ this evening for LSZ162-240>244-263-264.

  Heavy Freezing Spray Warning from 1 PM this afternoon to 7 AM
     EST Friday for LSZ243-244-264.

  Heavy Freezing Spray Warning from 11 AM EST /10 AM CST/ this
     morning to 5 AM EST /4 AM CST/ Friday for LSZ240>242-263.

  Heavy Freezing Spray Warning from 3 PM this afternoon to 7 AM
     EST Friday for LSZ245>247-265.

Lake Michigan...


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