Area Forecast Discussion
Issued by NWS Marquette, MI

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FXUS63 KMQT 122026

Area Forecast Discussion
National Weather Service Marquette MI
326 PM EST Thu Jan 12 2017

.SHORT TERM...(Today and tonight)
Issued at 416 AM EST THU JAN 12 2017

LES has lingered primarily across the Keweenaw and eastern portions
of the area this morning and should gradually weaken, if not diminish
in some locations this morning. The next system that will clip the
area later today is evident on water vapor satellite imagery with
energy digging across southern Saskatchewan and Manitoba. This system
is already showing signs of slowing its southward progress as the jet
streak appears to be getting ready to round the base of the
shortwave trough.

As the above mentioned system approaches the area, low-level flow
will back to the southwest across the area providing a brief break
or at least some weakening of LES in the northwest wind snowbelts
through the late morning/early afternoon. However, as this system
clips the region and lifts back north into Ontario, later this
afternoon/evening, an arctic airmass will filter south across the
area with 850mb flow veering to the northwest. This will allow for
LES to redevelop across the northwest wind snowbelts later today and
linger through the overnight hours. The main surface low is progged
to track over northern portions of Lake Superior; however, multiple
things are in play to see gusty winds across the area as this low
tracks north of the area. Not expecting winds to be as strong as we
experienced a few days ago as the stout pressure falls/rises will
remain well north of the area. The strongest winds should be
confined to the Keweenaw Peninsula and along the shoreline of Lake
Superior. Once the LES begins, could see a few hours of moderate to
at times heavy snow, but inversions start to lower through the
overnight hours so currently thinking that snowfall totals will fall
just short of LES advisory criteria. Given the strong winds expected
later this afternoon into Friday morning across the Keweenaw, expect
the blowing and drifting snow be become a problem. Therefore, have
opted to run with a winter weather advisory, primarily for the
impacts of blowing snow on visibilities and drifting of snow already
on the ground, and additional snow expected later today. Upon
collaboration, will let the day shift re-evaluate the potential for
similar impacts across eastern portions of the area as the strong
wind are not expected to arrive there until later tonight. The strong
winds will begin to diminish from west to east across the area
towards daybreak on Friday, but expect a bitter cold start to the day
as wind chills will drop below zero as the arctic airmass moves
overhead. Wind chills Friday morning look to range from -6 to -25,
with the coldest values expected in the interior west.

.LONG TERM...(Friday night through Thursday)
Issued at 326 PM EST THU JAN 12 2017

A hi pres rdg near the Great Lks wl bring generally dry wx to the
area this weekend. Although the weekend wl start on a seasonably
chilly note, there wl be a warming trend into early next week as upr
hgts begin to rise with the arctic branch retreating n into Canada
and an upr rdg building over the se CONUS. 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 wl probably be a mixed pcpn event
arnd Tue. Pacific air and well above normal temps wl dominate much of
next week.

Fri ngt/Sat...A clipper shrtwv embedded in the arctic branch flow is
fcst to track across Ontario to the n of a hi pres rdg stretching fm
the ne states into the Upr MS River Valley. A lo pres trof associated
with the clipper is fcst to cross Lk Sup during this time. But with
an absence of any sgnft mstr inflow and the passage of the sharper
dpva/deep lyr qvector cnvgc to the n closer to the shrtwv track,
expect any accompanying pcpn to be light and limited mainly to areas
near Lk Sup. Some of the guidance does show a weak disturbance
tracking thru WI and bringing some lgt pcpn to the scentral right
under the sfc rdg axis, but if this pcpn does occur it wl be light.
Depending on the cld cover associated with this disturbance, some
locations over the scentral could be quite chilly on Fri ngt with
lighter winds closer to the hi pres rdg axis 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 thru Sun ngt...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 downstream of a trof over the sw states. There wl be a slow
warming trend as h85 temps recover to -2C to -4C on Sun. Lowered fcst
min temps blo the consensus on Sat ngt in areas away fm lk
moderation with light winds and moclr skies.

Mon thru Tue ngt...Concern during this time wl focus on the timing/
pops/ptype associated with shrtwv/sfc lo pres lifting out of the sw
trof toward the Great Lks. Although Mon is likely to be dry until at
least early aftn, some of the faster models indicate some waa sn
well ahead of the sfc lo wl arrive over the scentral in the aftn.
While the longer range guidance continues to show some variability on
the fcst mass/thermal fields with uncertainty on the interaction btwn
the primary shrtwv and another disturbance in the plains, current
trends sug the heaviest pcpn wl fall on Tue and over the central and
ern cwa. Since the bulk of the models show h85 temps rising aoa 0C
over much of the cwa, the associated pcpn is likely to be wintry mix.

Wed/Thu...Expect a drying trend on Wed following the passage of the
disturbance/sfc lo pres to the ne. The zonal flow of Pacific air in
its wake is fcst to lift h85 temps as hi as 5C on Wed, so expect
well above normal temps. This warm, dry wx wl linger on Thu with the
persistent flow of Pacific air.

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 134 PM EST THU JAN 12 2017

A shortwave dropping into the area this afternoon will bring snow
showers and lowered CIGs to KCMX this afternoon, which will continue
as lake effect through much or all of tonight. Additionally, at KCMX,
strong W-NW winds will lead to blowing snow and further reduced VIS.

Most uncertain at KIWD where it appears only a short period of some
light snow showers late this evening into early tonight. Could go

KSAW will likely not see any snow, although some flurries can`t be
ruled out completely. No significant impacts otherwise.

.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 326 PM EST THU JAN 12 2017

Expect wnw gales to 35-45 kts under the tight pres gradient between
a lo pres moving into Quebec and hi pres building into MN to slowly
diminish under gale force late tonight with the slow approach of the
hi pres/flatter pres gradient. Not out of the question there could
be some storm force gusts this evng. The hi waves whipped up by the
strong winds and very cold arctic air surging into the area will
result in heavy freezing spray that will diminish on Fri as the
winds/waves subside. As the pres gradient sharpens between a lo pres
crossing Ontario and the hi pres moving to the e on Fri night, expect
sw winds to increase up to 30 kts and then shift to the w following a
lo pres trof passage on Sat. But then as the hi pres builds closer
later on Sat into Sun and lingers into Mon, expect winds to diminish
under 20-25 kts. As a lo pres approaches from the sw later on Mon
into Tue, winds will shift to the e-ne. Since this lo pres is
forecast not to deepen significantly, winds are now expected to
remain under 25 kts.

Upper Michigan...
  Winter Weather Advisory until 1 AM EST Friday for MIZ001-003.

  Wind Chill Advisory from 10 PM this evening to 10 AM CST Friday
     for MIZ009-010.

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

  Gale Warning until 4 AM EST Friday for LSZ245>251-265>267.

  Heavy Freezing Spray Warning until 11 AM EST Friday for

  Heavy Freezing Spray Warning until 9 AM EST Friday for LSZ243-

  Gale Warning until 1 AM EST /midnight CST/ Friday for LSZ162-

  Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Friday
     for LSZ240>242-245>247-263.

  Heavy Freezing Spray Warning until 11 PM EST /10 PM CST/ this
     evening for LSZ162.

Lake Michigan...


SHORT TERM...Ritzman
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